AnSlope Cruise III - NBP04-08 Cruise Report

 

Table of Contents

1      Introduction and Overview.. 2

1.1 The AnSlope Project 2

1.2 A Brief History of AnSlope. 2

1.3 A Rough Outline of Anslope-3 Operations and Science. 4

1.4 Acknowledgements. 8

1.5 AnSlope-3, Personnel 9

2 Program Reports. 10

2.1 CTD.. 10

2.2 Lowered Acoustic Doppler Current Profiler (LADCP) 11

2.3 Turbulence Measurements with “Vampire”. 14

2.4 Salinity (Autosal) and T/C Sensor Behavior 20

2.5 Dissolved Oxygen Titration. 23

2.6 CFC-Sampling. 27

2.7 Transient Tracers (He, Tritium, O-18) 32

2.8 Nutrient Sampling and Analysis. 32

2.9 XBT Transit and Underway Measurements. 39

2.10 Ship-mounted ADCP Measurements (SADCP) 45

2.11 Ship acoustic systems: influence of thrusters on on-station data quality. 48

2.12 Oceanographic conditions in northern iceberg field near 57.5oS. 50

3 Station Maps and Tables. 52

3.1 Station Maps. 52

3.2 CTD/LADCP Stations. 54

4 Other Project Reports. 58

4.1 Sea Ice Observations. 58

4.2 Marine Mammal Passive Acoustic Monitoring and Cetacean and Wildlife Diversity. 60

4.3 Ornithological Observations. 70

4.4 Educational/Public Outreach. 73

4.5 Satellite Imagery. 73

4.6 Weekly Reports. 77

4.7 Contact List 87

 


 

1      Introduction and Overview

 

1.1 The AnSlope Project

The primary goal of the AnSlope project is to better understand the physical processes that govern the transfer of dense shelf waters into the intermediate to bottom layers of the adjacent deep ocean, and the compensatory poleward flow of waters from the oceanic regime. Assuming that the upper continental slope and its typically associated Antarctic Slope Front (ASF) are the primary gateways for the exchange of shelf and deep ocean waters, four specific objectives have been identified: [1] Determine the mean ASF structure, its principal scales of variability (from ~1 km to ~100 km, and from tidal to seasonal), and its role in cross-slope exchanges and water mass mixing; [2] Determine the influence of slope topography (canyons, proximity to a continental boundary, isobath divergence/convergence) on frontal location and outflow of shelf water; [3] Establish the role of frontal instabilities, benthic boundary layer transport, tides and other oscillatory processes on cross-slope advection and fluxes; [4] Assess the effect of diapycnal mixing (shear-driven and double-diffusive), intrusive lateral mixing, and non-linearities in the seawater equation of state (thermobaricity and  cabbeling) on the rate of descent and fate of outflowing, near-freezing shelf water.   

The core field elements of AnSlope consist of CTD-O/rosette casts, bottom-moored current/temperature/salinity arrays, ship- and CTD-mounted Acoustic Doppler Current Profilers (ADCPs), microstructure profiling systems mounted on the CTD or operated independently in free-fall mode, geochemical analyses of water samples for chlorofluorocarbons (CFCs), helium, tritium and oxygen isotopes, and basic tidal modeling. On this cruise, no mooring work was done, the microstructure studies were accomplished independent of the CTD with a 'VMP,' and two ship-mounted ADCPs were operated in addition to dual LADCPs. Water samples were taken and processed aboard ship by representatives of the collaborating Italian CLIMA program, frequent sea ice observations were made according to AsPect protocols, and observers routinely logged marine mammals and seabirds along the ship's track.

The fieldwork phase of AnSlope has consisted of three dedicated cruises, two of which were completed earlier, in Feb-Apr of 2003 and 2004. On those cruises, bottom-moored arrays were set near the mouth of Drygalski Trough, recovered, and some reset for recovery in January 2005. In addition, a pre-AnSlope site survey was carried out from the NBP during December 2002 to better define the slope and shelf break area in the western Ross.

 

1.2 A Brief History of AnSlope

AnSlope 3 has had a rather checkered history. At the proposal stage, it was conceived as a complement to the summer A-1 and A-2 cruises, an opportunity to assess the ASF environment at its winter extreme. It was realized that the NBP would have some difficulty carrying out station work near Cape Adare in midwinter, but that end-of-winter conditions could as well be accessed in October and November, at which time the high salinity shelf water (HSSW) reservoir could be expected to be near its maximum volume. The work was anticipated to be difficult, nonetheless, so 65 days of ship time were requested, at a time between the two summer cruises when bottom-moored current, temperature, salinity arrays would be deployed and operating. The project was approved on the second round, but since then the 'late winter' component has been repeatedly altered by ship scheduling and related constraints.

First the requested Oct-Nov 2003 period was found to be committed to another project. In lieu of that time frame, a shorter, early-summer period was offered and accepted, partly on the rationale that more ground could be covered at that time of year, providing access to the ASF well beyond the Cape Adare region where the A-1 and A-2 would be tied down with mooring work. Indeed, earlier observations had suggested that the ASF might well be stronger in the eastern Ross. Planning for a Dec 2003 - Jan 2004 cruise was thus initiated, personnel committed and substantial time expended on organization and communications. Fairly late in this process, the issue of refueling the NBP in the Ross Sea was raised, and it was realized that the only viable option would be to draw >100K gallons from a USCG icebreaker midway during the cruise, at which time the Polar Sea/Star would be enroute to its channel work. The numbers looked reasonable, if tight, but a decision was made that it would not work, and shorter biology and geophysics cruises then assumed the available ship time. At this remove we do not have access to the notes and considerations that led to the revised schedule, but recall that USCG reluctance to lighten its load prior to working the thick, fast ice in McMurdo Sound was a deciding factor.

AnSlope-3 was then postponed to the Oct - early Dec 2004 period, a year later than originally requested, but consistent with a decision to redeploy some of the moorings for a second year during A-2. At that point in the game, A-3 could have been started earlier, due to an apparent weakness in the NBP schedule in September. However, we were still wary of being unable to work successfully in the NW Ross at that time, and eventually shortened the cruise by five days after analyzing available fuel usage information for past cruises in winter/spring. It did appear that 60 days could be managed, given a full load at the start and a conservative average burn rate of ~6250 gal/d. However, one day before flying south to begin a 60-day NBP04-08, we were informed by RPSC that the ship could only use 220K gallons of fuel between pit stops. That constraint, subsequently revised to 200K gallons in our sailing orders, reportedly resulted from a series of inclining tests and stability calculations that appeared to show the NBP could not meet 'damage stability' criteria under which she was chartered, without retaining about half of her fuel load as ballast. After initially thinking that it made little sense to attempt in ~30 days what was expected to be difficult in 60, we 'bit the bullet' and decided to try and make the best of being dealt another bad hand.

Since A-3 was to be a two-act opera, and satellite imagery showed that ice conditions in the Ross in early October were forbidding, we opted to try and work initially in a more accessible area of the continental margin, south of Tasmania. We had obtained summer data in that region in December 2000 - January 2001, and so knew something about its hydrography, both oceanographic and bathymetric. The ASF is not limited to the Ross Sea, but occurs at other locations along the Antarctic continental margin, where similar processes are believed to occur. In retrospect, this worked out reasonably well, as we were able to gain access to both the shelf break and interior shelf polynyas in a relatively short time. Meanwhile, we kept a satellite eye on the Ross Sea, and eventually decided to attempt work in that sector on the second A-3 leg, following a refueling in Timaru, NZ. Additional time was allowed for the Ross Sea work by departing the George V Coast area a few days early, and assuming that a longer period could be accommodated in the Ross by very conservative fuel use. In the end, that may have been a bad gamble, as we were caught by a major storm enroute to the Cape Adare region. This set us back by several days at the outset, as the NBP was advected NW and then had to cross compact, heavily ridged ice at great fuel expense in order to reach the study area. Otherwise, we found the late November Ross Sea ice to be workable, with plentiful leads, and more could have been accomplished with another 20,000 gallon of fuel. But as this report is being assembled, we are enroute to Lyttelton NZ, and expecting to arrive ~ five (science) days early.

Many already know that we have questioned the decision to hamstring the NBP prior to 04-08, knowing that she is no less safe at present than on numerous prior cruises. We have also argued against costly alterations to the vessel that appear to have worsened an initial problem, primarily to benefit a project that could most likely have been accomplished on other ships. We are concerned that proposed solutions to the existing 'damage stability' problem will cut further into the endurance that is so essential to effective use of a research vessel in remote polar regions. And we are weary of seeing a capable research ship spending more time on transit, in port and on 'hazmat' duty than doing the science for which it was ostensibly chartered, at considerable expense. But our responsibility is only to complain when we end up suffering for such decisions, however desirable or necessary, they may be judged by others. With that said, on to the achievements of this nearly completed cruise.

 

1.3 A Rough Outline of Anslope-3 Operations and Science

This cruise report is one of three primary documents resulting from A-3. Another is the set of DVDs that contain all of the relevant cruise data, and a third is the RPSC Data Report that includes more technical details about data acquisition, sensor calibration, etc. An appendix to the Cruise Report includes the weekly science reports that we are required to send to 'mo-sciweekly@usap.gov', and the Data Report includes the Marine Project Coordinator's daily 'sitrep' reports. The Cruise and Data Reports will be on the DVDs, which are distributed to AnSlope PIs and the CLIMA and Whale Observation programs, with copies to RPSC aboard ship and in Denver.

More than half of the A-3 CTD/rosette stations and VMP profiles were taken on leg 1, where the belt of pack between the ice edge and shelf break was narrow (~100 km), numerous grounded icebergs east of 150o E continue to hinder the westward movement of thick multiyear sea ice, and the coastal polynyas east of the Mertz Glacier Tongue were readily accessible. The work began with several cross-slope sections between ~149oE and 142oE (sample shown in Figure 1), shorter than occupied during NBP00-08, but sufficient to span the broad frontal region in that sector. This was followed by along-slope CTD and VMP work, a quick tour of open water areas deep on the shelf, and a final cross-slope transect.

New bottom water is clearly being formed, and deep water modified, along this part of the continental margin, and it is primarily a fresh variety that does not reflect much influence of the higher salinity water deep in the shelf troughs. Only our westernmost section showed a thin bottom layer on the upper slope with higher salinity, and that outflow was not pursued westward. Initially a large iceberg blocked further access to the slope region, and in the end a decision had by then been made to save time for use in the

 

 

Figure 1. Transect across the outer shelf and slope near 143o E (Figure A.1).  Panels show potential temperature, salinity, zonal velocity, meridonal velocity, and dissolved oxygen and a T-S diagram. Zonal and meridional velocities have had their means removed. Dissolved oxygen has been corrected according to the onboard calibration.

 


 

 

Ross Sea. But given the general properties of bottom water in the Australian-Antarctic Basin, HSSW may not be a significant contributor in this sector, much less to the global ocean. Deep water modification in this region is classic Carmack/Killworth large-scale interleaving, as has been noted previously, a process not often reported in the Ross sector. Waters over the upper slope were remarkably fresh, even in comparison to summer measurements. Modified Circumpolar Deep Water (MCDW) intrusions onto the shelf seemed relatively weak and shallow, and a tendency is noted for deep water and shelf water to enter/exit the shelf across or near the same sills. Of course that traffic keeps appropriately to the left, this being the southern hemisphere, and may also be evidenced by bottom temperature distributions on the slope. Shelf water formation was ongoing, albeit intermittently (see VMP section below), and we are increasingly convinced, as others may already know, that the smaller, less-heralded coastal polynyas, initially neglected in favor of the storied Mertz, are where the saltiest shelf water is formed. Ice Shelf Water (ISW) was also observed, but must compete with the effects of strong surface forcing in winter, and may be less apparent thereby.

On A-3 Leg 2, we began by occupying shallow, widely-spaced reference CTD stations across the eastern Ross Gyre, while moving southward through the pack near the prime meridian. Just prior to that time, satellite data suggested lower ice concentrations might be encountered across the eastern end of the Gyre, but that seemed like a long and potentially risky route to reach the AnSlope mooring sites. A substantial flaw lead north and slightly west of Cape Adare had beckoned for weeks, and appeared to be located near the shelf break, so we diverted SW toward it, across the Adare Trough. At that point we began to encounter much thicker, more compact ice, and had barely reached the downslope end of a planned transect when a large storm halted the proceedings. Persistent easterlies closed off the flaw lead and then strong SE winds moved us much farther NW than desired. Much fuel was consumed backing and ramming toward the SE before we were finally able to accomplish a transect across the 'Visbeck' mooring (Figure 2).

Ice and weather conditions then improved and remained good for the rest of our Ross Sea survey. Several sections were completed in the vicinity of the Drygalski Trough sill, one near the AnSlope moorings. VMP profiling near the Drygalski sill was followed by a section downstream and across the outer Joides Trough, and along the outer western axis of the Challenger Trough. By then it was time to begin heading north, and along that route short sections were occupied across the slope and outer Iselin Bank, ending with a deep cast at the northern side of a passage north of the Bank. On both legs of the cruise, XBT casts were utilized along some transects to guide station work, add detail to the lateral thermal structure, and save time.

The Ross sector was also found to be fresher than anticipated at this time of year, with the ASF more than a spring tidal excursion south of the continental shelf break. Both east and west of Iselin Bank, bottom water on the continental slopes indicated a fresh shelf water/surface water component, quite likely derived from the E-W flow that tracks the ASF. ISW continues to elude us on the slope, implying that little of it leaves the shelf in undiluted form, most of it recirculates back under the Ross Ice Shelf, or we have yet to stumble on its primary exit time/location during brief surveys. The apparent weak roles of

 

 

Figure 2. Transect across the outer shelf and slope near 173°E (Figure A-2).  Panels show potential temperature, salinity, zonal velocity, meridonal velocity, and dissolved oxygen and a θ-S diagram. Zonal and meridional velocities have had their means removed. Dissolved oxygen has been corrected according to the onboard calibration.

 

 
both ISW and HSSW near the shelf break at this time of year present an interesting puzzle, one that may require more than the narrowly-focused AnSlope data sets to solve.

Conversely, deep water and its derivative intrusions onto the shelf were alive and well, dominating much of the subsurface water column and often extending to the sea floor. Has the HSSW reservoir shrunk to a point where it can no longer keep the MCDW/CDW at bay? Are we witnessing a response to the anomalous sea ice and glacial ice conditions over the shelf during recent summers? Were the A-3 measurements obtained at a time when the forcing was weak and the ocean regime was relaxing after a more active period caused by the large storm? We trust that the moorings, when recovered in January 2005 and analyzed in conjunction with the meteorological and sea ice data, will shed additional light on these issues.

The following sections in this report provide more detail about the profiling, water sampling and underway observations made on A-3. Most all CTD stations were sampled for CFC, dissolved oxygen and salinity, vs. 58% and 44% on A-1 and A-2, respectively. Relatively few helium, tritium and oxygen isotope samples were taken on station, but many more nutrient samples in order to accommodate onboard processing by the CLIMA group. Many more XBT casts were also made on A-3, mostly enroute to and from the study areas, and the accompanying underway sampling was not done on prior AnSlope cruises (see Section 2.9). As the station table (Table A-1) in the appendix demonstrates, about 12 days were spent in each of the two study areas, out of about 55 days at sea and another 5 days in port. Future inspection of RPSC records will show the NBP 'sailing for science' more than 90% of the time during A-3. However, when actual time on site is closer to 40%, it may be time for another rubric to monitor NBP performance.

 

1.4 Acknowledgements

We thank the many people who have contributed in many ways to the AnSlope 3 adventure, aka NBP04-08.  From the responsive and responsible ECO/RPS hands, to the conscientious and congenial science party, all have persevered with talent, care and good humor. We also thank OPP O125172, for which we have tried to give good weight in return.  We may have spurned Hobart and ranted at Holik, but from Denver to Palisades, Seattle to Suitland, McMurdo to Timaru, many others have helped to see us through.  From a perfect storm off Cape Adare to a perfect finish across the ACC, from here to there and back again, we now have some icy tales to tell.

 

 


1.5 AnSlope-3, Personnel

 

Science Staff

Stan Jacobs

Chief Scientist

LDEO

Gerd Krahmann

LADCP/CTD/tracer sampling

LDEO

Robin Robertson

CTD/XBT/underway sampling

LDEO

Deb LeBel

CFC sampling/analysis

LDEO

Guy Mathieu

CFC sampling/analysis             

LDEO

Raul Guerrero

CTD/autosal/sample analysis

LDEO/INIDEP

Sarah Searson

CTD/XBT/underway sampling

LDEO

Alison Criscitiello

Oxygen/tracer sampling

LDEO

Basil Stanton

Oxygen/sampling analysis

LDEO/NIWA

Laurie Padman

VMP/ AnSlope PI/

Earth & Space Research

Loren Mueller

VMP/CTD/XBT

Earth & Space Research

Denis Franklin

Sea ice observations

LDEO

Ian Southey

Sea ice/ sea bird observations

LDEO

Sarah Dolman

Marine mammal observations

IWC/ WDCS

Kelly Asmus

Marine mammal observations

IWC/ Deacon University

Alessandra Campanelli

nutrient sampling

CLIMA/ ISMAR-CNR

Serena Massolo

nutrient sampling

CLIMA/ Universitá di Genova

RSPC Support Staff

Karl Newyear

Marine Projects Coordinator

Annie Coward

Marine Technician

Amy West

Marine Technician

Jeff Morin

Marine Science Technician

Sheldon Blackman

Electronics Technician

Kevin Pedigo

Electronics Technician

Rob Hodnet

Information Technician

Dean Klein

Information Technician

 

LDEO = Lamont-Doherty Earth Observatory

CLIMA = Climate Long-term Interaction of the Mass balance of Antarctica (Italy)

INIDEP = National Institute for Fishery Research (Argentina)

IWC = International Whaling Commission

NIWA = National Institute for Water and Atmospheric Research (New Zealand)

WDCS = Whale and Dolphin Conservation Society

 


2 Program Reports

 

2.1 CTD

Temperature, salinity, and dissolved oxygen profiles were obtained with a SeaBird Electronics SBE 911+ CTD system fitted with 2 sets of ducted conductivity-temperature sensors, dual pumps, and one/two SBE 43 dissolved oxygen sensors. The sensor suite was mounted vertically on a flat surface just inboard of the lower CTD/rosette frame supports. As the sensor pairs gave slightly different values and drifted slightly with time (sea section 2.4.), post-cruise calibration plus intercomparisons with bottle data will be required during data reduction. A transmissometer and fluorometer were also installed, both with 6000 m-depth capability. One Hertz GPS data from the vessel's Ashtech GPS was merged with the CTD data stream and recorded at every CTD scan. Data were acquired using a PC running Windows 98 and SeaBird's Seasave software, version 5.30b. Raw data were copied over the network to a separate drive immediately after station completion. Processed data were copied to a network disk drive and were generally available within minutes after station completion.

Spiking and modulo error counts were of increasing concern during the first leg of the cruise, and led to analyses suggesting a conducting cable fault in the vicinity of 600 m. After considerable discussion, the outer 700 m of cable was lopped off after station 79, enroute to Timaru, followed by a new end termination and test cast near the end of XBT transect #2 (station 80). These measures did not totally eliminate either the spikes or modulo errors, but reduced them to insignificant levels during the 2nd leg.  Station 57 needed to be restarted due to pump tubing problems. At station 98, the pump hose for the primary sensors was dislodged when bottles were fired. Consequently, data values for station 98 subsequent to 47 db are suspect.  The pump for the secondary sensors was found to be operating incorrectly at the start of station 132 and was replaced.

Most profiles reached within 10 m of the sea floor, with bottom approach guided by a 12 kHz pinger (OSI) mounted on the frame, along with an SBE bottom contact switch fitted with a 10 m lanyard and weight.  The pinger and bottom contact switch generally worked well, except for a few stations where the ship drifted rapidly and/or the bottom current was strong, or where the ship's thrusters complicated the bottom approach. (See section 2.11 below.)  Transmissometer readings were nearly constant for all casts except # 85, which is puzzling, since early data in this region indicated significant suspended material near the bottom. In an attempt to determine whether the instruments might be at fault, transmissometers were switched in and out before various casts (20, 29, and 81) and the transmissometer cable was changed (cast 9).  The surface reference marker on the CTD cable indicated the depth of the CTD beneath the surface was changed before casts 5 and 80.

Water samples were taken with a 24-position SBE 32 Carousel sampler with 10 liter 'Bullister' bottles. Water was collected for onboard analyses of salinity, dissolved oxygen, chlorofluorocarbons (CFCs) and nutrients (silicate, phosphate and nitrate). Salinity and oxygen analyses are primarily for standardizing the CTD conductivity and O2 sensors. Additional samples were drawn on some stations for later analysis at LDEO and in Italy of helium, tritium, oxygen isotopes and nutrients. The rosette was generally trouble free except for minor problems such as trip failure due to sticky latches, open vents and dislodged O-rings, as noted on the bottle cop sheets. Most bottles were closed on most stations, but usually two or more were fired at each chosen depth, as the water columns encountered rarely required more detailed sampling. Sample depths emphasized water column extrema in T and S, regions with homogeneous layers for salt and O2 control, and layers near the sea surface and sea floor.  Several experiments were conducted with tripping procedures, such as cycling already closed bottles to greater depths on yo-yo stations, and tripping during the upcast without stopping. The fish was typically raised and lowered near 50m/min, but slower near the air and sediment interfaces.

Station setup was more problematic than we encountered on prior NBP cruises, often requiring more than 30 minutes from the time a decision was made to stop for station until the ship was ready for the CTD to be launched.  This complicated related preparations, such as starting the LADCP system, and on one occasion an LADCP connector was deep fried as the package went over minus its dummy plug. Time required to get the CTD out of the water and back into the relative warmth of the Baltic room was also of concern, given –20oC air temperatures at some stations. While the CTD sensors seemed to withstand such thermal shock without incident, we cannot easily account for all jumps that occurred, e.g. between sensor output and bottle oxygen values. On the other hand, some time was saved by limiting the O2 sensor equilibration time at 4 m depth to 1-2 minutes prior to each station. We do not believe this negatively impacted O2 sensor performance, which was less good overall than expected from these new instruments. After rather large offsets and jumps during leg 1, a second O2 sensor was added, beginning at station 88, with some improvement. Hysteresis also continues to plague these sensors, although much less so that the earlier Beckmann oxygen units. See section 2.5 for more details on the bottle-CTD oxygen comparisons.

Against some prior advice, and after a full round-house discussion, the Baltic room was made available for VMP casts rather than undertaking that operation on deck and in the wet lab. To protect the CTD during the 12-24 hr VMP stations, during which time the Baltic room door was open, the CTD/rosette was shunted aside, but not disconnected from the conducting cable. It was covered with a tarp, kept warm by a small heater and the sensors were drained. This procedure worked reasonably well, although water was left on the sensors during the last VMP cycle, and a heater may have failed, perhaps accounting for a coincident shift in the secondary conductivity sensor output (see section 2.4.). As noted above, all the CTD temperature, salinity and oxygen data will be reprocessed after post-cruise sensor calibration data are available. At that time it will be determined whether the primary or secondary sensor outputs, or some combination of the two, will be used for the final data set. [Stan Jacobs]

 

2.2 Lowered Acoustic Doppler Current Profiler (LADCP)

A dual head (one up and one downward looking) lowered ADCP (LADCP) system was attached to the CTD/rosette for the entire cruise. Three different heads were used. All units were versions of the 300kHz “workhorse” type. During leg one to the George V Coast, the upward looking system (SN 5254) was a loan from RDI, the ADCP manufacturer manufacturer, while the downward looking was the most reliable unit owned by Lamont (SN 149). SN 5254 is a newly developed head with a stronger output power. RDI thereby hopes to extend the range of the workhorses under difficult conditions such as the low amount of scatterers in parts of the deep ocean.

During test station 1 the battery case developed a leak through which sea water came in contact with the battery pack. This was not noticed directly after the cast. A few days later (there was a 5 day gap between the test and the second station) it was found that one endcaps of the battery case had been blown off. It was not clear whether the alkaline batteries exploded themselves or whether electrolysis caused the failure of the endcap assembly. As the battery case was heavily corroded a spare battery housing was prepared and installed.

During the first few stations unit SN 5254 developed one bad beam. As the RDI workhorse systems each have four transducers they can still operate with one failing transducer. Only the error estimate of the velocities is lost in this case. Unfortunately this system developed a second failing transducer, which rendered it inoperable. Also, we did not find that 5254 provided a significantly longer range. After cast 12, when the second transducer failed, we removed both systems from the rosette.

The data gathered until then was of reasonable acoustic quality at most stations. All profiles in the George V Coast region were, however, plagued by the close proximity to the south magnetic pole. In this region the flux gate compass from which the ADCPs derive their heading does not work reliably. During the first leg of the cruise an attempt was made to derive ADCP heading from other data. So far we have not been able to create a method of recovering the heading over the full length of a profile. Under some circumstances the developed algorithm, which is based on the assumption that the current measured by the ADCP does not change much over the 1.5 second ping interval, is able to recover parts of the rotation. In these cases it is possible to compare the flux gate measured heading with the independently derived rotation and evaluate the quality of the measured heading. In a few cases this evaluation indicated that the measured heading was reliable in spite of the proximity to the south magnetic pole.

After e-mail consultation with colleagues at LDEO we resumed LADCP operations at station 49 with SN 150 as the upward looking unit. Except for the unusable compass data both profilers worked well.

Before station 58, the dummy plug was not placed on the CTD/rosette side of the connection between ADCPs and computer. One of the power holding pins of the  plug corroded away during the cast. This rendered unusable the second quintopus cable, which connects the battery with the two ADCPs and the deck cable. The first had been found early during the cruise to be unreliable. ET Sheldon Blackman cut the corroded part off the second cable and replaced it by the same part of the uncorroded, but unreliable, first cable. He built a high pressure safe connection between the two salvaged pieces. A replacement cable ordered from the manufacturer did not reach the ship in time for our mid-cruise port call in Timaru, NZ. A new battery housing was received but has not been used.

During the second leg of the cruise no serious problems were encountered. SN 149 developed one broken beam but remained otherwise fully functional.

Previous experience with LADCP systems in the Southern Ocean indicated that profiles going deeper than about 1500m give unreliable results as the amount of scatterers at these depths is too low for the RDI workhorses. Several such profiles lead to suspicious looking results.

All in all, about 50 out of 100 LADCP profiles were located far enough from the magnetic south pole and shallow enough for a sufficient amount of scatterers. Table A-2 in the appendix lists the LADCP profiles taken and whether they are deemed reliable

 

Figure 3: Example LADCP profile showing a three layered current structure.

 

after being processed with the current version of the processing routines (see Figure 3 for a profile deemed reliable). As the processing routines are under continuous development, we always hope that future advances will result in additional reliable results. [Gerd Krahmann]

 

2.3 Turbulence Measurements with “Vampire”

Operations Summary

The Vertical Microstructure Profiler (VMP, a.k.a. “Vampire”; see photo on Figure 4) is a tethered, free-fall profiler measuring microscale (order 1 cm) temperature and conductivity (T and C), and velocity shears u/z and v/z.  Vampire also carries pumped calibrated CTD-quality T and C sensors (SeaBird SBE-3 and SBE-4), for providing simultaneous high-accuracy (but lower vertical resolution) scalar data. Instrument depth and motion (speed and tilt) are monitored by a pressure sensor and 3‑axis accelerometer.  The latter data provide a means for removing instrument-induced “noise” from the shear sensors.  The instrument fall speed w is ~0.6 m/s, the rate determined by a balance by syntactic foam buoyancy elements and a “chimney sweep” drag brush.  The chosen fall speed is a compromise between sensitivity of the shear probes (µ w2: i.e., better at higher w) and the vertical resolution of the microscale scalar sensors (better at lower w).  Vampire is ~2.2 m long when fully assembled.

The primary goal of deploying Vampire on AnSlope-3 was to obtain higher-quality measurements of turbulent mixing rates than we obtained on AnSlope-1 using the CTD-mounted Microstructure Profiling System (CMiPS).  In particular, we hoped to obtain turbulence data through the upper interface of the bottom-trapped plumes of outflowing dense shelf water, as seen in AnSlope 1 CTD/LADCP/CMiPS data.

Vampire was deployed from the Baltic Room, replacing the CTD there for periods of a few hours to a day.  Once the technique for converting the Baltic Room was sorted out, turnover took about 2 hours to set up for Vampire, and 1.5 hours to return to CTD operations.

Maximum deployment depth was ~800 m.  We had ~1300 m of cable available on the winch drum, and could have deployed deeper if there had been a good scientific justification.  However, because Vampire “kites” with the drag on the cable due to the lateral motion of the ship (generally tied to wind-driven ice motion) relative to the deep ocean currents, the amount of line that must be unspooled from the winch is generally greater than the instrument’s final depth.  Thus, we tentatively estimate a maximum profiling depth of ~1000 m for the present winch cable.

Mechanical Issues

 The main technical problem we encountered with Vampire deployment was with the winch drum.  This drum was re-engineered from a standard commercial model in order to accommodate more cable (for deeper profiling).  However, the drum flanges were not strong enough to support the pressure exerted by the cable during retrieval: as a result, the drum flanges were warped, and subsequently rubbed against the supporting winch frame.

Data Storage

Vampire data are included on the Cruise CD.  The data are provided in Matlab format, and are listed as “raw_data” and “processed_level_1”.  The raw-data files are in counts (digitized voltages and frequencies) as originally recorded directly off Vampire. The process-level_1 files are a quick-look version of data in engineering units. These data require further post-processing, but contain versions of all the signals that are useful to look at. Setup files (*.setup; ASCII text), list basic information about configuration for each deployment.

Each file contains header and data structure arrays (HDR and DATA).  See Matlab documentation for how to access contents of structure arrays.  HDR data are profile start time, time base (always UTC here) and the limits used for trimming bad data off the start and end of the original data files (using “trim_files.m”).  DATA arrays are in two forms, “fast data” and “slow data”. For the first two deployments in AnSlope 3, the fast and slow sampling rates were 512 Hz and 64 Hz, respectively.  For reasons explained below, these rates were reduced to 256 Hz and 32 Hz for the third deployment. Table 1 shows signals in the DATA structure array. Information in structure arrays is accessed as follows:

load A3_001_030.mat;   % load process_level_1 file, giving HDR and DATA

                                             %   structure arrays

Pf = DATA.P_fast;         % etc.

 

 

 

Variable

Units

Sample rate

Description

 

 

 

 

Ax, Ay, Az

m s-2

Fast

3-axis accelerometer

tilt

degrees

Fast

Derived from Ax, Ay, Az

P_fast

Dbar

Fast

Pressure record for fast channels

P_slow

Dbar

Slow

Pressure record for slow channels

W

m s-1

Fast

Fall speed

Sh1, Sh2

s-1

Fast

Velocity shear from airfoil probes

T_SBE

oC

Slow

SBE-3 temperature

C_SBE

 

Slow

SBE-4 conductivity

S_SBE

psu

Slow

Salinity from T_SBE and C_SBE

t_f

s

Fast

Time (seconds) for fast channels

t_s

s

Slow

Time (seconds) for slow channels

T1_lo

oC

Fast

FP07 T1 low-resolution

T1_hi

oC

Fast

FP07 T1 pre-emphasized (high-res)

dT1dz

oC m-1

Fast

FP07 T1 gradient

T2_lo

oC

Fast

FP07 T2 low-resolution

T2_hi

oC

Fast

FP07 T2 pre-emphasized (high-res)

dT2dz

oC m-1

Fast

FP07 T2 gradient

C_raw 1

 

Fast

Raw output for C_dC

 

1 Microconductivity not available on AnSlope 3. 

 

Table 1: Parameters sampled by Vampire, and their sampling rate categories.

 

Results

A total of 60 good profiles were obtained in 3 sessions as described below (see also Table 2, below). One profile is shown in Figure 4.  Graphical summaries of all processed_level_1 profiles are on the cruise CD/DVD as *.PNG graphics files.

 

Deployment 1: Intrusions along the George V Land Coast shelf break

Vampire was deployed for a period of ~20 hours in sea ice over the upper slope in the George V Land region (AnSlope 3, first leg).  22 profiles were obtained in this period. The ship generally drifted with the ice, with one repositioning (after profile A3_001_012) to move the ship up the slope closer to the shelf break.  The data set provides information on the turbulence associated with interleaving intrusions of cold shelf water and warm offshore water of CDW origin.

The number of intrusive layers frequently corresponded to the number of high-backscatter layers visible in the 38 kHz Ocean Surveyor vessel-mounted ADCP.  There are a few potential explanations for this observation, ranging from the two water types (“shelf” and “offshore”) having distinct scatterer populations, to the higher backscatter that is expected theoretically, associated with high variance of high-wavenumber thermal (and hence sound speed) gradients.

 

Deployment 2: Upper-ocean response after katabatic winds in the Mertz Polynya

Vampire was deployed for a period of ~6 hours in the open water of the coastal polynya along the edge of the Mertz Glacier Tongue. 10 profiles were obtained in this period. The ship used dynamic positioning (“DP”) to stay in an exact location and with a consistent orientation to the wind.  Deployment was initiated during a period of intense offshore katabatic winds, with speeds of 50-60 knots, and clear visual evidence of rapid surface cooling and ice formation.  Unfortunately for our science interests, the wind dropped to ~10 knots during the ~2-h taken to convert the Baltic Room to Vampire use.  However, the air temperature remained cold, below -10oC.  The data set provides some information on the turbulence energetics of the surface mixed layer under moderate convective conditions, but we were frustrated at being so close to a “katabatic” data set and missing it.  Nevertheless, from preceding CTD operations in the harsh conditions, it is clear that the ship is capable of operating (with CTD or Vampire from the Baltic Room) in high-wind, ice-free, high-convection conditions using DP rather than free drift.

 

Deployment 3: Mixing over the Drygalski Trough sill

Vampire was deployed for a period of ~24 hours in sea ice over the sill at the northern end of the Drygalski Trough.  28 profiles were obtained in this period.  Winds were light, and the ship drifted in a rough ellipse presumably driven by ocean tidal currents and perhaps some near-inertial (wind-forced) variability.  The data provide information about mixing between an intrusion of Modified Circumpolar Deep Water (MCDW) and the cold surface layer and cold, dense bottom layer.  A sample profile from this deployment (A3_002_023) is shown below (Figure 4). 

We experienced two problems during this station.  First, upon original setup, the data acquisition system reported many “Bad Buffers”, symptomatic of noisy or erratic communication with the instrument.  After consulting the manufacturer over Iridium phone, we lowered the communication baud rate and instrument sampling rate (the latter from 512 Hz to 256 Hz).  This did not solve the problem, and the cause of the signal noise was ultimately determined to be the deck cable leading to the winch.  The entire data set was acquired, however, at the lower sampling rate.  The second problem was that we accidentally bottom-crashed Vampire after drop A3_002_012, breaking the microstructure sensors. The crash occurred because of the way Vampire is deployed: in order to obtain good data, cable is let out faster than the instrument falls, so that the real-time displayed pressure at Vampire is not a good indication of how deep the instrument will ultimately fall. We need to mark the wire accurately, and also monitor ship-recorded water depth more carefully.   Displays of depth from the Bathy-2000 (“BAT”) system are in “uncorrected meters”, i.e., based on a sound speed of 1500 m s-1.  For accurate approaches towards the seabed, we also need to account for the ~1% difference between depth (in m) and pressure (in dbar).

The data from this deployment show a strong modulation of mixing rates in the MCDW intrusion during the day.  Data were collected just after neap tides for this region; nevertheless, it is likely that mixing rates are influenced by variations of the predominantly diurnal tidal currents during the course of a day. We were not able to test the variability in mixing between spring and neap tides, but we take the present data set as indicating that tides are an important contributor to mixing of MCDW intrusions and dense shelf water in the northern trough and over the sill. This is a potentially significant preconditioning mechanism for determining the average volume and density of shelf water exiting the NW Ross Sea troughs.

Acknowledgments

A large number of people contributed to Vampire operations on AnSlope 3.  We thank Annie Coward and Jeff Morin (RPSC) for working out the mechanics of how to deploy Vampire from the Baltic Room, and helping to implement the solution.  Amy West and Karl Newyear (RPSC) also contributed to converting the Baltic Room between CTD and Vampire use.  Alison Criscitiello, Raul Guerrero, Robin Robertson, Sarah Searson and Basil Stanton all helped with Baltic Room Vampire operations.  The ship crew’s ability to keep workable space around the Baltic Room is gratefully acknowledged.  The name “Vampire” was coined by Robin Robertson just before Halloween.

[L. Padman and L. Mueller]


Table 2:  Details of Vampire profiles during AnSlope 3

 

Profile  ID     Date      Time      Lat      Lon    File size

                        (UTC)                           (bytes)

 

Deployment 1: George V Land Shelf Break

A3_001_010.mat  25-Oct-2004 13:18:34  -65.922  144.602  19289784

A3_001_011.mat  25-Oct-2004 13:44:52  -65.921  144.606  53301784

A3_001_012.mat  25-Oct-2004 14:47:58  -65.918  144.616  78382784

A3_001_013.mat  25-Oct-2004 15:41:20  -65.916  144.624  79766784

A3_001_014.mat  25-Oct-2004 16:51:04  -65.913  144.635  84837784

A3_001_015.mat  25-Oct-2004 17:51:54  -65.911  144.643  82993784

                                                                 Moved South 2.5 km, A3_001_016.mat  25-Oct-2004 21:27:52  -65.935  144.654  66272784   up-slope towards

A3_001_017.mat  25-Oct-2004 22:24:42  -65.936  144.659  74017784   shelf break

A3_001_018.mat  25-Oct-2004 23:43:30  -65.937  144.661  76313784

A3_001_019.mat  26-Oct-2004 00:19:38  -65.937  144.661  74017784

A3_001_020.mat  26-Oct-2004 01:12:54  -65.937  144.660  53792784

A3_001_022.mat  26-Oct-2004 01:18:34  -65.938  144.660  19161784

A3_001_023.mat  26-Oct-2004 02:18:48  -65.938  144.656  68280784

A3_001_025.mat  26-Oct-2004 03:20:46  -65.937  144.650  69509784

A3_001_027.mat  26-Oct-2004 05:07:34  -65.937  144.614  61323784

A3_001_028.mat  26-Oct-2004 06:11:34  -65.936  144.599  59888784

A3_001_029.mat  26-Oct-2004 07:08:18  -65.936  144.582  60821784

A3_001_030.mat  26-Oct-2004 07:38:44  -65.936  144.573  10981784

A3_001_031.mat  26-Oct-2004 07:45:16  -65.936  144.570  14427784

A3_001_032.mat  26-Oct-2004 08:03:46  -65.937  144.564  47645784

A3_001_033.mat  26-Oct-2004 08:34:52  -65.937  144.553  53362784

A3_001_034.mat  26-Oct-2004 09:08:28  -65.937  144.539  47901784

Deployment 2: Mertz Polynya

A3_001_035.mat  29-Oct-2004 03:44:58  -67.056  145.178  76785032

A3_001_036.mat  29-Oct-2004 04:21:40  -67.056  145.178  56528024

A3_001_037.mat  29-Oct-2004 04:51:22  -67.056  145.178  53153888

A3_001_038.mat  29-Oct-2004 05:22:44  -67.056  145.178  44035288

A3_001_041.mat  29-Oct-2004 06:36:34  -67.056  145.178  44087104

A3_001_042.mat  29-Oct-2004 06:58:48  -67.056  145.178  44867392

A3_001_043.mat  29-Oct-2004 07:29:44  -67.056  145.178  41162040

A3_001_044.mat  29-Oct-2004 07:52:14  -67.056  145.178  39350512

A3_001_045.mat  29-Oct-2004 08:14:08  -67.056  145.178  33438408

A3_001_046.mat  29-Oct-2004 08:44:00  -67.056  145.178  79168568

Deployment 3: Drygalski Trough Sill

A3_002_002.mat  22-Nov-2004 19:32:08  -72.216  172.960  15928664

A3_002_003.mat  22-Nov-2004 20:19:56  -72.222  172.967  27171720

A3_002_004.mat  22-Nov-2004 21:06:08  -72.229  172.976  22909704

A3_002_010.mat  22-Nov-2004 22:13:44  -72.234  172.993  27233696

A3_002_011.mat  22-Nov-2004 23:11:44  -72.238  173.006  27171720

A3_002_012.mat  22-Nov-2004 23:59:30  -72.240  173.018  26078504 Bottom-crash

A3_002_014.mat  23-Nov-2004 01:33:38  -72.248  173.040  26421912

A3_002_015.mat  23-Nov-2004 02:18:56  -72.251  173.051  29440448

A3_002_016.mat  23-Nov-2004 03:20:24  -72.255  173.067  29441464

A3_002_017.mat  23-Nov-2004 04:06:08  -72.255  173.082  25953536

A3_002_018.mat  23-Nov-2004 04:50:08  -72.255  173.095  27015256

A3_002_019.mat  23-Nov-2004 05:38:06  -72.257  173.110  28514872

A3_002_020.mat  23-Nov-2004 06:24:50  -72.257  173.128  26016528

A3_002_021.mat  23-Nov-2004 07:15:16  -72.255  173.147  32428504

A3_002_022.mat  23-Nov-2004 08:05:56  -72.254  173.167  28483376

A3_002_023.mat  23-Nov-2004 08:49:56  -72.251  173.183  26859808

A3_002_024.mat  23-Nov-2004 09:33:32  -72.248  173.196  25828568

A3_002_026.mat  23-Nov-2004 10:50:10  -72.240  173.205  27952008

A3_002_028.mat  23-Nov-2004 11:38:48  -72.236  173.205  27889472

A3_002_029.mat  23-Nov-2004 12:29:08  -72.231  173.199  28763144

A3_002_030.mat  23-Nov-2004 13:16:20  -72.228  173.191  29766280

A3_002_031.mat  23-Nov-2004 14:06:16  -72.227  173.181  28170448

A3_002_032.mat  23-Nov-2004 14:43:20  -72.227  173.174  27358664

A3_002_033.mat  23-Nov-2004 15:28:58  -72.228  173.164  26640352

A3_002_034.mat  23-Nov-2004 16:14:06  -72.230  173.155  26140480

A3_002_036.mat  23-Nov-2004 17:01:40  -72.235  173.148  26140480

A3_002_037.mat  23-Nov-2004 17:58:50  -72.241  173.143  28295416

A3_002_038.mat  23-Nov-2004 19:02:16  -72.248  173.143  29357136



Figure 4: Example Vampire profile from Deployment 3 over the sill at the northern end of the Drygalski Trough.  Location is shown as a red dot on the map (upper center).  Upper right: T-S relationship from Seabird (CTD-quality) sensors.  Middle left: profile of fall speed (m s-1). Middle center: profiles of temperature from SeaBird SBE-3 (blue) and FP07 microstructure sensor (red), which is calibrated against the SBE-3.  Middle right: profile of salinity derived from Seabird sensors. Lower left: profile of microscale gradient, T/z, from FP07 thermistor.  Lower center: profile of velocity shear, u/z, from airfoil shear probe (only shear-1 installed for this profile).  Lower right: photo of Vampire being prepared in the Baltic Room.

2.4 Salinity (Autosal) and T/C Sensor Behavior

In order to monitor the performance of the CTD conductivity sensors, 818 salinity samples were analyzed using the on-board autosals. Autosal SN 59-213 was used for stations 1 to 88 (518 samples), while stations 91 to 142 were measured on Autosal SN 61-670 (300 samples). Both instruments performed within factory specifications, although instrument 59-213 required lowering the flow rate to obtain adequate repeatability. Laboratory temperature control was excellent, remaining 1 to 2ºC below the setting temperature (24ºC). The fan set up on top of one of the salinometers kept the lab temperature vertically homogeneous.  Data from the Autosals were captured using the ACI 2000 hard/software package. The connection failed on 3 occasions, but without a clear pattern, we were unable determine the cause. This occurred with both autosals, using the ACI and a home made box (probably from SCRIPP’s), and two 50 way ribbon cables. ACI did not reply to email inquiries concerning this problem.

An average of two boxes (48 samples) was measured on each “run” with standardization performed at the beginning and end of each.   The standards for calibration came primarily from batch P140 (OSI) from November 2000 (approx. 44 vials) plus three P141 vials from June 2002 and two P143 vials from February 2003, for inter-calibration.  On three occasions (Runs 3, 16 & 19), vials from two different batches were used consecutively without finding differences between them. As seen in Table 3, little or no re-standardizing was required between runs. The Standby reading for instrument 213 ranged from 6135 to 6141 while instrument 670 varied from 6067 to 6072. For reference, 5 units change in the Standby readings is equivalent to .00005 CR units or about 0.001 psu.

Errors in salinity resulting from the primary and secondary conductivity sensors were tracked throughout the 142 stations (Figure 5). Salinity errors, denoted DeltaS, are reported as rosette salinity minus CTD salinity. The primary conductivity sensor showed a stable bias from station 1 throughout station 133. Mean Delta S was -0.0015 with a standard deviation of 0.0022. For the estimation of this error, 655 points out of 761 (86 %) were used. Points excluded were greater than 1.5 times the standard deviation of the mean error. The secondary sensor started with a DeltaS @ +0.0075 and decreased down to near 0 around station 50. As this sensor’s DeltaS is neither constant nor linear, it may not be as suitable as the primary for final calibration. Both sensors appear to drift from station 134 to 138 and from station 139 to 142 the offsets are constant at much higher DeltaS values  (+0.010 for the Primary and +0.0044 for the Secondary).  

 

 

Run

1

2

3

4

5

6

7

8

9

10

11

12

213

6139

6139

6138

6138

6141

6137

6138

6135

6140

6141

6137

6138

 

 

 

 

 

 

 

 

 

 

 

 

 

Run

13

14

15

16

17

18

19

20

 

 

 

 

670

6069

6072

6071

6071

6071

6069

6068

6067

 

 

 

 

 

Table 3: Salinometer Standby readings throughout the cruise. Good stability was observed between runs as little or no re-standardizing was needed.

 


Although the drift in DeltaS values coincided with Autosal run # 19, no problems were observed in the pre- and post-standarizations of the salinometer. Standby readings also showed no significant change relative to prior or subsequent runs. Finally, the rate of change in DeltaS is larger for the primary sensor (change in DeltaS of +0.0115) than for the secondary sensor (where change was less than +0.005), as shown in Figure 5. This differential behavior was also observed in the salinity difference between the primary and secondary sensors (see below). After station 140, the primary conductivity sensor was soaked (for 15 min.) and flushed with a 1% solution of Triton X 100.  No subsequent changes in the offset were observed.

Applying a linear correction as a function of ‘Sta#’ for 134-138 and a constant offset +0.010 for 139-142, the residual has a standard deviation of 0.0022.

Comparison among Primary and Secondary CTD sensors

  Differences between the T sensors (Pri-Sec) are constant around -0.001 throughout the cruise. Differences in S between the conductivity sensors are more complicated, and include the following features:

-   A gradual drift toward near zero on the secondary sensor from station 1 to 52 (Figure 6).

-   A jump (probably in the secondary sensor) between stations 80 and 81, coincident with the Timaru port call, in spite of the fact that both sensors were flushed and kept filled with DI water at that time. The aft dry lab distiller, that provided DI water for the sensors, was out of service. Sensors were flushed after each station only with filtered water.   

-   The anomalies at station 98 were caused when the primary hose was knocked off when a bottle was fired at 47 db.

-   A jump between stations 110 and 111 (not obvious in DeltaS from the bottles) occurred at the time of a VMP station staged from the Baltic room. With the door open, the CTD package was covered and TC sensors were warmed by a heater. However, on this occasion, the TC plumbing was left with filtered water on, the heater was found off and water in the plumbing was slushy. 

-   Station 111 shows a larger S0-S1 than typical, and a result from tripping bottles while the CTD was underway.

From station 134 to 138 the difference between primary and secondary drifts, as observed in both sensors when compared against bottle salinities. However, the primary sensor showed a steeper drift than the primary. The cause of this drift is unknown, but could be oil or biological coating/stain on the electrodes that may change their geometry. It could also be a problem within the CTD. SBE technical services might be consulted to check out, which could require factory service.

-   From station 139 to 142 the difference between primary and secondary sensors returned to a constant value, but much higher than before. Both sensors then differed from the bottle data by +0.010 and +0.0044, primary and secondary, respectively.

Along XBT sections, thermosalinograph (TSG) salinities were comparies with samples drawn from the sea surface water system and analyzed with the Autosal.  Out of 111 samples, 109 were used to estimate the preliminary error of the TSG.  The error was constant throughout the cruise with a mean value of –0.005 psu and a standard deviation of 0.011 psu. [Raul Guerrero]

Text Box: Figure 6: Difference in salinity (S) and temperature (T) between primary and secondary sensors at the time of bottle closing

 

2.5 Dissolved Oxygen Titration

A SBE43 dissolved oxygen sensor was incorporated in the CTD sensor array. At CTD stations water samples were drawn from selected rosette bottles for dissolved oxygen analysis using the modified Winkler method. Whole bottle samples were titrated using an amperometric titrator designed by Dr. C. Langdon. An RPSC titration unit was used while other laboratory equipment, sample flasks and chemicals were supplied by LDEO.

Titrations were done on 865 CTD samples and 181 surface samples from the 4 Transects between New Zealand and Antarctica. No major problems were encountered with the oxygen analyses. The usual minor problems such as bubbles in the micro burette or sticking of bottle top dispensers occurred occasionally. Initially some difficulty was experienced in getting stable blank determinations and this may have been due to inconsistent performance of the 1 ml standard dispenser. However this eventually settled down and is not thought to have affected O2 results. Sensitivity analysis of the WHP O2 equation shows that final accuracy is only very weakly affected by the blank value. Standard determinations showed some variation but these were within the usual accepted range.

Comparison of the rosette O2 and the primary CTD O2 sensor data showed that the sensor was reading consistently low.  The Delta O2 (rosette – CTD) at each station (color coded for in situ temperature) are shown in Figure 7. Note that the 3 panels in this figure are plotted with some overlap to show the changes over time. Delta O2 values were typically in the range 04 - 1.2 ml/l, and the temperature dependence is evident with the largest Delta O2 values at low temperatures. The figure also shows there were variations with time throughout the cruise. These variations were a slow drift over time interspersed with periods of apparent stability. On occasions there was an apparent abrupt change in O2 sensor calibration while on station. This occurred at Stations #52 and #98 and accounts for the outliers at these stations. The problems at Station # 98 are covered in the CTD section of the report. Another outlier at Station #124 has been checked and remains unexplained.

Plotting Delta O2 against CTD Temperature for all data showed the clear decrease in Delta O2 with increasing temperature up to a temperature of 2.0, with a generally flat response at higher temperatures. The All Data plot showed a large spread but suggested that a simple temperature correction could be found by taking stations in similar groups suggested by Figure 7. Figure 8 are plots of Delta O2 against temperature for  all 142 Stations in 8 groups. For each plot a least squares straight line has been fitted for the data at temperatures below 2o C. The straight line parameters and Root Mean Square deviations of Delta O2 from the straight line are given for each panel. We believe these parameters should be used in the final post processing of the CTD O2 data.

An additional SBE43 sensor was installed on the CTD at Station #88, as a secondary while retaining the original primary sensor. Comparison of these sensors showed a mean difference of 0.336 ml/l, with the secondary sensor reading higher than the primary sensor. Consequently the secondary sensor values were closer to the rosette data. The standard deviation between the primary and secondary sensors was 0.094 ml/l.  The Delta O2 (rosette-secondary sensor) exhibited a similar tendency to the primary sensor with higher values of Delta O2 at the low temperatures.  These Delta O2 data are shown in Figure 9a with a fitted straight line as was done for the primary sensor.  After removal of the temperature effect, Figure 9b shows a quadratic curve fitted to the residuals to remove the pressure dependence, while Figure 9c shows the residual Delta O2 after removal of both temperature and pressure trends. It can be seen that the remaining variation is very small with a standard deviation of 0.039 ml/l.

The surface water samples on the four transects (see Figure 10) between New Zealand and Antarctica were drawn from the thermosalinograph sea water system in the wet lab. Some problems were experienced with fine air bubbles in the water flow and as a result extra care was needed in taking these samples. Even then on occasion, fine air bubbles could form (presumably from out gassing) within the flask during the interval between sampling and titration. When this occurred appropriate comments were added to the log sheets. [Basil Stanton]

 

 

Figure 7: Difference between titrated and CTD-measured dissolved oxygen. The color of the dots indicates the temperature.

 

 

 

Figure 8: Temperature dependency of the dissolved oxygen deviation between CTD sensor and titrated measurements.

 

 

Figure 9: Delta O2 variation for the secondary O2 sensor.

 

 

Figure 10: Titrated dissolved oxygen content on XBT transect 3.

 

2.6 CFC-Sampling

Water sampling

Water samples were collected using 10-l Niskin-type bottles with coated internal springs and baked o-rings. CFC samples were the first samples taken and were drawn into 100-ml precision ground glass syringes. The syringes were capped with stainless steel Luerlock caps and stored in a sink filled with uncontaminated surface seawater. Tension was maintained on the syringe plunger with rubber bands and the samples were analyzed within 12 hours of collection, typically less.  For most of the cruise, the water bath temperatures were less than -1.0C, which ameliorated any potential degassing during sample storage.

Sampling from the uncontaminated seawater line

Water samples were collected on all four transits between New Zealand and the ice.  On the first two transits, samples were collected every two hours; on the second two transits every 30o of latitude.  Sampling was simply a matter of inserting the tip of the syringe into the length of Tygon tubing providing flow to the syringe water bath and following standard rinse and storage procedures.  Data quality statistics (see Data Quality section) were not significantly different from samples drawn from the rosette. 

Water sample analysis

 From the syringes, the water samples were injected through a three-way valve into a calibrated glass volume (approximately 35 cc, calibrated to better than 0.1%). The three-way valve and the calibrated volume were flushed with sample water prior to taking the aliquot for analysis.  

The water in the calibrated volume was subsequently transferred to a glass stripper chamber where the dissolved gases were purged with ultra high purity nitrogen, which was also used as the gas chromatograph carrier gas. The released CFCs were concentrated by adsorption on a unibeads 2S cold trap at –70°C. Subsequently the trap was isolated and heated to 100°C. The desorbed gases were then backflushed into the chromatographic columns using ultra pure nitrogen. Cooling was accomplished with liquid CO2 and heating was done electronically. The entire stripping, trapping and GC analysis procedure was automated with a Shimadzu Chromatopac C-R8A used to control the sequential steps of the procedure.

Air sample collection and analysis

Air samples were drawn from an interface with the ship's on-board pCO2 measurement system.  Aliquots of air taken from this line for CFC analysis were passed through magnesium perchlorate to remove water vapor, isolated in a calibrated sample loop, and then analyzed in the same way as standard gases (see section on calibration). Samples were only collected when the wind direction was from the bow to avoid contamination with the ship’s atmosphere.

Gas chromatography

The CFC analysis system consisted of a Lamont-built purge and trap system interfaced to a HP 6890 gas chromatograph which contained a precolumn (stainless steel, 3 foot length, 0.085 inch ID packed with 80-100 mesh Porasil B) and a main column (stainless steel 5 foot length, 0.085 inch ID packed with 60-80 mesh Carbograph 1AC) mounted in the GC oven and maintained at a constant temperature of 90°C. The main column was followed by a 0.085 inch ID, 4 inch long stainless steel column packed with 80-100 mesh mol sieve 5A. This was mounted outside the GC oven and maintained at 50°C. Its purpose was to separate CFC-12 from N2O and it was valved out of the gas stream after CFC-12 eluted. The detector was operated at 260°C. The chromatographic run required 8 minutes and the total analysis time was 10 minutes per sample. 

CALIBRATION

Procedure

The response of the electron capture detector to different amounts of CFCs was calibrated by filling 10 different sized calibrated loops attached to a multiport valve with a gas mixture (CFCs in nitrogen) of known CFC content. Loops were filled individually and after relaxation to ambient temperature and pressure, the standard gas was concentrated onto the cold trap and subsequently injected into the gas chromatograph by the same procedure used for water samples. Calibration curves were run approximately once a week during the course of the cruise and one of the standard volume loops

was run frequently (at least every other hour) to check for drifts in the detector’s response between calibration curves.

Standard

 Lamont standard 842 was used on this cruise. It was calibrated before and after the cruise against an air standard (Lamont standard 35078) that had been analyzed at R. Weiss’ laboratory. The CFC concentrations on the SIO98 scale for this standard are:

CFC-11:           387.83 pptv

CFC-12:           200.49 pptv

CFC-113:          105.82 pptv

PROBLEMS

A high CFC-11 stripper blank (-0.078 t 0.369 pmol/kg, averaging 0.003 pmol/kg) persisted for most of the cruise.  We believe this is due to a small secondary peak overlapping with the CFC-11 peak, and post-cruise corrections will be made on shore.

DATA QUALITY

Stripping efficiency

Stripping efficiencies were measured approximately every day throughout the cruise.  The overall averages were 99.8% for CFC-11, 99.7% for CFC-12 and 99.3% for CFC-113. The efficiencies for CFC-12 and CFC-113 would be expected to be higher than CFC-11 because of their lower solubility.  However, the CFC-12 and CFC-113 concentrations were lower than the CFC-11 concentration for the samples used in these determinations and thus are more sensitive to small uncertainties in blanks. We do not believe the stripping efficiency is less for CFCs 12 and 113 than for CFC-11 and a correction has not been made for stripping efficiency for any of the CFCs.

Blanks

System and stripper blanks were measured for every 6-8 water samples that were run and are presented in Tables 4 and 5.  The stripper blanks averaged about 0.003, 0.007, and 0.010 pmol/kg for CFCs 11, 12, and 113 respectively.  Blank corrections were made by interpolating between blank determinations made before and after a given analysis, and variability in blanks had little effect on the data quality.

Rosette bottle/sampling blanks could not be determined for this cruise because CFC-free water was not sampled. In cruises where we have been able to determine such blanks, they have been in the range of 0.002 to 0.005 pmol/kg. We have not applied a correction for bottle/sampling blank to this data set.

Precision

The precision of the measurements was monitored throughout the cruise by making replicate measurements. For atmospheric measurements, 3-6 replicates were measured at each location. For water measurements duplicate samples were collected at most stations.

The average precisions of the atmospheric measurements were 1.26%, 1.42%, and 2.44% for CFCs 11, 12 and 113 respectively.  Mean mole fractions were 251.7 ppt, 537.66, and 79.88 ppt.

The average differences between duplicates with CFC-11 concentrations greater than 1 pmol/kg were 1.2% for CFC-11, 0.5% for CFC-12, and 1.7% for CFC-113.  The average differences for  concentrations less than 1 pmol/kg were 0.007 pmol/kg for CFC-11, 0.003 pmol/kg for CFC-12, and 0.003 pmol/kg for CFC-113.

Duplicates were drawn on approximately 80% of the samples taken from the uncontaminated seawater line.  The average reproducibility was 1.1%, 0.7%, and 1.7% for CFC-11, CFC-12, and CFC-13, respectively.

RESULTS

Underway Measurements

     We compared samples drawn from the surface bottle (~3 m) from six stations with water drawn from the uncontaminated seawater supply (~7 m) when the CTD was at the surface at the end of the cast (Table 4).  The average difference was 2.23%, 1.26%, and 1.01% for CFC-11, CFC-12, and CFC-113, respectively.  These differences are only slightly larger than the average precisions for Leg I, during which the comparisons were made.  This suggests that underway measurements for CFCs can provide useful information, assuming an uncontaminated seawater supply of the same quality as the Palmer's.

We completed four transects between New Zealand and 65-70oS.  The four transects reflect a change from late winter to early spring conditions, with the southern ends of

 

CFC-11 (pmol/kg)

CFC-12 (pmol/kg)

CFC-113 (pmol/kg)

CFC-11 Difference (pmol/kg)

 CFC-12 Difference (pmol/kg)

CFC-113 Difference (pmol/kg)

Underway

5.492

2.994

0.540

-

-

-

Station 2

5.402

2.923

0.527

1.67

2.43

2.47

Underway

4.997

2.709

     0.490

-

-

-

Station 3

4.885

2.687

     0.489

     2.29

0.82

0.20

Underway

4.469

2.522

0.418

-

-

-

Station 30

4.348

2.468

     0.415

2.78

2.19

0.72

Underway

4.675

2.542

0.445

-

-

-

Station 46

4.492

2.504

0.441

4.07

1.52

0.91

Underway

4.600

2.548

0.444

-

-

-

Station 47

4.667

2.557

0.452

1.44

0.35

1.77

Underway

4.662

2.566

0.439

-

-

-

Station 57

4.611

2.572

0.439

1.11

0.23

0

 

Table 4 CFC concentrations for six pairs of stations where both surface rosette and underway samples were collected together and the differences in concentrations between the samples

 

Transects 1 and 2 occurring off George V Land and those of Transects 3 and 4 in the Ross Sea. 

Concentrations at 7 m (Figure 11) typically reflect the thermal structure.  Variations are more weakly correlated with salinity variations, as expected from the solubility function for CFCs (Warner and Weiss, 1985).  This initially confirmed the plausibility of the measurements.  Highest concentrations were observed between 60oS and 65oS (Figure 11), reflecting a balance between decreasing surface temperatures and ice cover slowing gas exchange.

On all four transects, saturations decline essentially monotonically between 57oS and 65oS (Figure 11). Supersaturations were observed north of about 47oS and are probably due to warming of the surface waters.  On Transects 1 and 2 saturations rose to a maximum at the thermal front at 57oS and decreased again to the south.  On Transect 3, no thermal front was observed, with no associated increase in saturations.  Saturations also dropped markedly south of 65oS on the last two transects, where we observed heavy ice cover.

Saturations of CFC-12 are typically about 3% higher than CFC-11 and about 9% higher than CFC-113 (Figure 11).  This likely reflects differences in gas exchange rates, which depend on the molecular weight of the species. [Deborah LeBel]


  

 

Figure 11. CFC concentrations and saturations for the three species along the XBT transects.


 

2.7 Transient Tracers (He, Tritium, O-18)

Stations with indications of possible meltwater were sampled for He, Tritium and  18O.  On some other stations, only 18O was sampled, mainly near the surface and seafloor.  Samples were drawn by A. Criscitiello and G. Krahmann according to the sampling procedures provided.  48 He channels, 48 Tritium bottles and 147 18O bottles were filled from CTD/rosette casts and 162 18O samples were taken underway near the sea surface from the onboard sea water lines.  The tracer samples will be analyzed at LDEO. [Alison Criscitiello]

 

2.8 Nutrient Sampling and Analysis

Approximately 1400 nutrient samples were drawn and processed aboard the ship. About 1150 seawater samples were taken from Niskin bottles on all CTD/rosette stations, the remainder were taken from the ship underway system during the four XBT transects between Antarctica and New Zealand (Table 6).

 

 

No. Samples

Date

Underway 1

108

15-20 October 04

Underway 2

67

1-4 November 04

Underway 3

45

7-15 November 04

Underway 4

72

30 November – 5 December 04

CTD George C Land area

595

20-31 October 04

CTD Ross Sea

572

12-30 November 04

Tot.

1459

57 days

Table 6. Number of nutrient samples collected during AnSlope-3.

 

Material and methods:

Seawater samples were filtered using GF/F Whatman filters (0.7 mm) and immediately stored at -80°C until analysis. Samples were unfrozen using a warm water bath (35-40°C) in order to bring them to room temperature immediately prior to analysis.

Analyses were carried out using an Autoanalyzer TRAACS 800, according to the colorimetric method suggested by Strickland & Parsons (1972).

The determination of nitrate and nitrite uses the procedure whereby nitrate is reduced in nitrite at pH 8 in a copper-cadmium redactor. The nitrite then reacts under acidic conditions with sulphanilamide to form a diazo compound that then couples with naftileliendiamina hydrochloride (NEDD) to form a reddish-purple azo dye that is measured at 550 nm.

The determination of soluble silicate is based on the reduction of a silico molybdate compound in acid solution to molybdenum blue by ascorbic acid. Oxalic acid is introduced to the sample to minimize interferences of phosphate. The absorbance is measured at 660 nm.

The determination of phosphate is based on the colorimetric method in which a blue compound is formed by the reaction of phosphate, molybdate and antimony followed by reduction with ascorbic acid. The reduced blue-phospho- molybdenum complex is read at 880 nm.

Data processing software AACE, designed by Bran and Luebbe, was used during analysis and allowed us to check standard quality.

Duplicate analyses, involving samples stored with different methods (described below), were taken at some stations in order to check whether nutrients (in particular, silicate) were adversely impacted by freezing. In fact, it is well known that a correct sample storage is particularly important for silicate determination when silicate content is higher than 50 mM, as in the case of Southern Ocean water masses. Silicon tends to polymerize when stored frozen and samples must be allowed to stand at room temperature before analysis. Tests carried on 55 samples showed that there is not any significant difference among concentrations found in samples analyzed just after sampling and after frozen storage (differences are < 5%, so very close to method precision), showing that no systematic error was made. In addition, a small set of samples (15) were stored in dark, cold conditions (+4°C) for 5 days before analysis. The concentrations for these samples are very similar to the ones obtained for those stored in the two previously described ways.

Furthermore, we checked our standard solutions with some other standards made up for intercomparison purposes.

During the cruise a quality problem with one of the Nanopure systems was detected in the nitrite and phosphate analyses. The use of Low Nutrient Sea Water (LNSW), brought on board at the refuelling stop in Timaru, allowed us to run nitrite samples on board. But problems in phosphate analysis persisted even using LNSW. Reagent tests and standard intercomparison did not reveal any analytical faults and in addition, phosphate analysis results were very sensitive to the ship movements. Since this kind of problem persisted during the whole cruise, it was decided to process these samples in Italy.  Samples of the standard solutions prepared on board will be shipped to Italy together with the phosphate samples in order to control the data quality. Furthermore, about 70 samples were collected from CTD stations at different depths and from the underway system and they were frozen (-80°C) just after sampling. These samples, together with standard solutions run on board, will be processed in Italy using a five-channel Autoanalyzer Technicon II. Results will be compared with the ones obtained on board for intercomparison purposes and will be used for more sample storage tests.

Analysis of the last samples taken from underway system during the 4th  XBT transect will be finish on board at the end of the transect if sea conditions permit, otherwise samples will be analysed in Italy.

Results:

Leg I – George V Land Coast

Measurements in the George V Land Coast area were carried out in early spring (2nd half of October). During this period in the shelf area, the water column exhibited only small ranges of temperature, salinity and nutrients, suggesting that the water column was well mixed. In fact no vertical trend can be identified in nutrient concentrations, which range from 70 to 90 mM and from 25 to 29 mM for silicate and nitrate respectively.

In the surface layer low temperature and relatively high salinity indicate that the melting process is not pronounced, and as a result nutrient concentrations are relatively high at 69.1 ±10.5 mM for silicate and 26.8±2.2 mM for nitrate.

At the slope area we can observe the CDW intrusion on to the shelf at depths greater than 200 m. This water mass can be identified not only from its physical characteristics,

 


 


 

 

Figure 13. Vertical profiles of temperature (°C), salinity, nitrate (mM) and silicate (mM) in casts 121-127 (Ross Sea).


 

but it can be traced also by high nutrient concentrations. In particular, silicate is a good tracer for this water mass ,which is characterized by concentrations ranging between 80 mM and 127 mM (99.3±11.3 mM as mean value), but the silicate maximum can often be found a few hundred meters below the temperature maximum, as already observed by other authors (Gordon et al., 2000). Nitrate shows a distribution more homogeneous than silicate also in the slope area, with the highest values (about 30 mM) coincident with the temperature maximum. “NO“ mean  level of  473±22 mM was calculated for CDW at the temperature maximum; this value falls in the same range as those calculated for the Weddell Sea (Lindegren&Anderson, 1991)

As an example, Figure 12 shows vertical profiles of temperature (°C), salinity, nitrate (mM) and silicate (mM)  in section 20-24, across the slope. Bottom concentrations, both for nitrate and silicate, are slightly lower than those found at the temperature maximum,

showing a possible influence of shelf water overflow, which agrees with the  temperatures below 0°C.

Comparing our data with results obtained during a previous cruise carried out in the same area in austral summer (end December 2000- mid January 2001) (Jacobs et al., 2005), we can see that, as a consequence of the heating and melting processes and the biological activity, surface nutrient concentrations in summer are lower than concentration found during this survey. Moreover, during the previous survey nitrate concentrations found in the MCDW core are a little higher than our data.

Leg II - Ross Sea

Measurements in the Ross Sea area were carried out in the spring period (second half of November), about 20 days later than the previous measurements in the George V Land area.

The shelf area surface layer was a little warmer and fresher, suggesting the beginning of an increase in solar radiation and dilution by melting of sea ice. In this condition nutrient concentrations were still high in the surface layer (77.1±9.3 mM for silicate and 25.8±2.7mM for nitrate) and nearly constant with depth. At some stations the nutrient minimum was not associated with the surface layer but it could be found around 40-80 m depth (e.g. stations 94, 99, 103, 109, 126, 127). Moreover, results showed that surface nutrient minima could be found in correspondence with fresher water (for example, in station 124, 126 and 127, shown in Figure 13).

In the slope area, we observed the intrusion of CDW on to the shelf and its mixing with shelf waters, more intense in the area off Cape Adare and along 175°W.

As an example, Figure 13 displays vertical profiles of temperature (°C), salinity, nitrate (mM) and silicate (mM) found in section 121-127.

CDW intrusion can be traced by nutrient high concentrations, which are around 29 mM for nitrate and around 110 mM for silicate. As already observed in the George V region, silicate traces better than nitrate the intrusion of CDW. In fact, nitrate is characterized by a more homogeneous vertical profile. In many cases silicate maxima were observed near the bottom (concentration increase toward the bottom by 10-15 mM), indicating dissolution of silica at the interface water-sediments. “NO” levels found at the temperature maximum (460±27mM) are very close to the ones reported for the same area (Rivaro et al., 2003).

At some stations on the shelf (i.e. station 121) the presence of ISW, was indicated by a temperature minimum near the bottom (about 500 m depth). This water mass is characterized by nitrate concentrations of 29-31 mM and silicate concentrations around 80-90 mM.

Comparing our results with data collected in the same area during the austral summer (February 2003) by CLIMA project, we can observe some significant differences concerning the surface layer.

During summer meltwater dilution and warming of surface waters are at their maximum. In fact, temperature and salinity (-1.43°C; 33.88) are significantly lower than the spring values. Moreover, summer surface nutrient concentrations were lower (21 mM for nitrate and 60 mM for silicate, as mean values) than spring data obtained during this cruise and the nutrient vertical profile is characterized by a stronger vertical stratification.

XBT transects- underway sampling

Surface samples were collected from the underway system during 4 XBT transects from New Zealand to Antarctica and vice versa.

Underway samples revealed a sharp increase in nutrient concentrations, in particular for silicate, from 58°S to 60°S, coincident with a strong decrease in temperature. Nitrite concentrations were undetectable (< 0.02 mM) in nearly all samples, but when they are detectable they show an inverse trend compared to the other nutrients, decreasing from north to south.

As an example, Figure 14 displays the XBT 1 section (15th to 20th October), in which the sharp increasing in silicate concentrations (from 10-15 mM to 50-55 mM) and the strong decreasing in temperature can be observed from 58° S to 60° S. Nitrate instead increased more regularly moving from north to south, with concentrations ranging from 10-12 mM at 54° S to 25-30 mM at 66° S, as shown in Figure 15. The same trend was observed in the XBT 2 (1st to 3rd November) and XBT 3 (7th to 15th November) transects. During the XBT 3 transect the increasing in silicate concentrations were particularly sharp from 60° S to 64° S. These results fall in the same ranges as those measured by other authors (Brzezinski et al., 2003). XBT 4 transect sample analyses are still in progress. In order to obtain a more robust dataset about seasonal evolution of surface nutrient concentration from New Zealand to Antarctica, we plan to analyze nutrients in seawater samples collected during XBT transects which will be made during the Italian-Antarctic survey at the beginning of January 2005 and at the end of February 2005. [Serena Massolo and Alessandra Campanelli]

References:

Brzezinski M.A., Dickson M.L.,Nelson D.M.; Sambrotto R. (2003). Ratios of Si, C and N uptake by microplankton in the Southern Ocean. Deep-Sea Research II 50, 619-633.

Gordon L.I., Codispoti L.A., Jennings J.C., Millero F.J., Morrison J.M., Sweeney C. (2000). Seasonal evolution of hydrographic properties in the Ross Sea, Antarctica, 1996-1997. Deep-Sea Research II 47, 3095-3117.

Jacobs S.S., Mele P.A., Smethie W.M., Mortlock M.A.(2005). Summer oceanographic measurements near the Mertz Polynya (140-150°E) on N.B. Palmer cruise 00-08. Cruise report.

Lindegren R., Anderson L.G. (1991). “NO” as conservative tracer in the Weddell Sea. Marine Chemistry 35; 179-187.

Rivaro P., Frache R., Bergamasco A., Hohmann R. (2003). Dissolved oxygen, NO and PO as tracers for Ross Sea Ice Shelf Water overflow. Antarctic Science 15 (3), 399-404.

Strickland J.D.H. & Parsons T.R. (1972). A practical handbook of seawater analysis. Bull. Fish. Res. Bd. Canada 167. 

Figure 14. Temperature and silicate concentration versus latitude in XBT section 1 (15-20 October).

Figure 15. Temperature and nitrate concentration versus latitude in XBT section 1 (15-20 October).

 

2.9 XBT Transit and Underway Measurements

Since A-3 was ordained to make four crossings of the Antarctic Circumpolar Current in order to obtain a few weeks time over the continental slope and shelf, we utilized the otherwise idle time to conduct an enhanced underway sampling program. While some of our transits were along routes that have been profiled since the IGY, such work has less commonly been done this early in 'the season'. XBTs extend the surface temperature record to depths of several hundred meters and reveal the positions and structures of the Polar, Subantarctic and other frontal features. It is also of interest to know whether the properties of near-surface waters are changing over time, since they help to set the characteristics of Antarctic Intermediate Water, which spreads far northward into more temperate latitudes. In addition Antarctic surface waters are presumably exchanged, if typically ignored, across the ASF.

The underway work consisted of dropping XBTs at regular intervals on each transit south of the Campbell Plateau. Transects to and from the George V Coast stopped at the ice edge; those in the Ross sector were continued southward into the sea ice. The XBT casts were supplemented on NBP04-08 by periodic underway sampling for dissolved oxygen, nutrients, CFCs, TCO2 and oxygen isotopes, some continued well onto the Plateau. A representative XBT section appears in Figure 16, and examples of the underway chemical data are shown in Figures 10, 11, 14-15 and 17. In addition, other underway data are routinely recorded aboard the NBP, as illustrated by the daily plots in Figures 18-20, along with ADCP measurements as shown in Section 2.10 (Figures  21-22).  Trackline bathymetry (not shown) was also logged along most of the ship’s track, but as much time  was anticipated to be in heavy ice, multibeam data was not recorded.

Comments about the underway data are included in some of the Program Reports.  We have noted earlier that undersaturations are significant in CFC and dissolved oxygen south of the Polar Front, probably due to the entrainment of deep water, and particularly under the sea ice where surface equilibration is damped. Larger temperature and salinity changes are associated with the Subantarctic Front than the Polar Front, and eddies are common between these features, but they are not the only contributors to mesoscale variability in the ACC. Two examples of that variability from NBP04-08 are the strong oscillating currents at near-inertial frequencies observed with the NBP's new 38 kHz Ocean Surveyor ADCP (Weekly Report #5), and perturbations in several near-surface parameters caused by a large field of melting icebergs north of the polar Front (Section 2.12).[Stan Jacobs]

 

 

 


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 17. Transect of CFC-11, -12, and –13 concentrations for the third XBT transect – caption to be supplied by Deb along with the figure.



Text Box: Figure 17.  Sample navigational data supplied by RPSC, see RPSC Data Report for further information.


Text Box: Figure 18.  Sample meteorological data supplied by RPSC, see RPSC Data Report for further information.


Text Box: Figure 19.  Sample surface water data supplied by RPSC, see RPSC Data Report for further information.

 


2.10 Ship-mounted ADCP Measurements (SADCP)

Ship-mounted Acoustic Doppler Current Profilers (SADCP) were used during both cruise legs to observe ocean currents.  Two systems were used, one for the first time after its installation a few weeks prior to the cruise. In comparison to the older 150kHz system, which has a range of up to 400m, the new 38kHz profiler is able to measure ocean velocities at depths of up to 1500m.

After a small problem at the beginning of the cruise when the shipboard processing of the ADCP data was not functional (data was however recorded during that time), the two systems worked reliably in most open water conditions. As had been found on many previous cruises, the collection of ADCP data on RVIB Nathaniel B. Palmer is severely limited under ice breaking conditions probably because of broken ice floes covering the ADCP well at the bottom of the ship. We found that this problem is the same for the new 38kHz system.

Both working areas had ice cover near 100% for most of the cruise. Thus little useful SADCP data was collected during transits between stations. On a number CTD and VMP stations, when the ship was not breaking ice, good data was collected. Unfortunately we found that the usage of bow and stern thrusters also created unfavorable conditions for the ADCPs. At stations of particular interest we thus let the ship drift with wind and ice for several more minutes after the CTD/rosette had been taken on board. Thereby we were able to obtain a few reliable current profiles at these locations. A more permanent solution that prevents ice floes from covering the ADCP transducer well would, however, be much preferable.

Figure 21 and 22 show the SADCP data collected by the two systems during transects 1 and 2. The top three panels display the zonal velocity component as measured by the old 150kHz system, the 38kHz system in broadband mode, and the 38kHz system in narrowband mode. The 38kHz system operates interleaved in a narrow and a broadband mode. The narrowband mode has, at the cost of lower resolution, a deeper range than the broadband mode. We found that data collected with both modes agrees within their limitations. Data collected with the 38kHz system also agreed well with data collected by the 150kHz system. The 38kHz broadband mode appeared to have a lower tolerance to adverse environmental conditions than the narrowband data. And both 38kHz modes were in turn less reliable than the 150kHz  system.

Analysis of the times when the 38kHz system provided fewer reliable current measurements showed high correlations with wind speed and pitch and roll movements of the ship (Figures 21 and 22, lower two panels). This finding is likely being caused by the ship's motion misaligning the transducer heads from the direction in which they had sent out their signal. We found that the data quality degraded strongly at pitch-roll angles of more than about 7 degrees. Such movements are encountered rather frequently in the Southern Ocean, but RVIB Nathaniel B. Palmer appears to be stable enough for us to expect the 38kHz system to provide reliable data under most conditions. The relatively small angle of 7 degrees beyond which the data quality degrades might, however, mean that on a ship more prone to rolling motions or operating in adverse conditions like Drake Passage, such as the ARSV Laurence M. Gould, only less reliable data could be  collected. [Gerd Krahmann]

 

 

Figure 21. Zonal currents measured by the two SADCP systems during the first transect from New Zealand to the George V Coast region. The lower two panels show the measured windspeed and the maximum pitch-roll angle within one minute intervals.

 


Figure 22. Zonal currents measured by the two SADCP systems during the second transect from the George V Coast region to New Zealand.  The lower two panels show the measured wind speed and the maximum pitch-roll angle within one minute intervals.

2.11 Ship acoustic systems: influence of thrusters on on-station data quality

The quality of data from the ship’s Bathy-2000 (“BAT”) depth recorder and acoustic Doppler current profiler (ADCP) systems (both the old 150 kHz and new 38 kHz) is strongly influenced by ship operational conditions.  Underway in ice, no useful signals are received from either BAT or ADCP: there is no obvious way around that, although future icebreaker designs should consider whether maintaining an ice-free area under the hull around the transducers is feasible.  The current lack of underway-in-ice data, however, places a premium on obtaining good data from both systems while on station; e.g., while doing CTD and water sampling profiles.  Choices made by the bridge watch profoundly affect data quality for both systems.

During AnSlope 3 we noted the following specific problems:

1.   During one station (CTD 130) in about 1000 m of water, we found that BAT was reporting a rapidly shoaling bottom (by about 150 m in several minutes), even though ship drift and known bathymetry suggested that water depth should be increasing.  While the entire screen of the BAT was noisy (typical of underway-in-ice and many on-station records), the apparent bottom return was extremely clear.  Since the CTD was approaching the seabed, we asked the bridge to turn off the thrusters long enough to get a clean BAT record.  The BAT depth immediately returned to the value expected from our drift and charts.

2.   On some occasions we were unable to get a clean signal from the CTD pinger, which is used to judge when the CTD is approaching the seabed. As with BAT, the solution was to request that the thrusters be turned off while bottom approach was completed and until the CTD was headed up, safely clear of the seabed.

3.   The ADCP systems are capable of ranges of ~300 m (150 kHz) and ~1000-1400 m (38 kHz) while the ship is underway in open water and low sea states. The new 38 kHz unit is a great addition to the Palmer, allowing deep currents to be measured over the entire Antarctic continental shelf and the dynamically important upper slope. However, while on station in the ice, we frequently obtained little or no information from either system.  As with the BAT, the key to getting good on-station data is to have significant time periods with no or low thruster activity.

In talking with the First Mate, Scott Dunaway, it appears that the forward thruster is likely the principal source of noise on the science acoustic systems, since it is closest to the transducer windows in the hull.  Both the forward and aft thrusters are used to keep the port (usually leeward) side against an ice floe while equipment is deployed from the Baltic Room on the starboard side aft.  However, at times when we have requested the thrusters be turned off or at least reduced, we have been able to get a significant time interval (>30 minutes) of quiet acoustic data before the bridge watch determined a need to re-power the thrusters.  That is, it appears the amount of thruster power used to maintain contact with the port-side floe is frequently more than is needed.  For science data return, the optimum conditions are to use the thrusters the minimum amount needed to maintain the ice-free space around the Baltic Room (mainly achieved with the stern thruster and main engine wash), and maintain an acceptable CTD wire angle.  Holding the ship firm against the ice on the port side is unnecessary provided the right conditions are met on the starboard (working) side.

 

Thrusters are essential to expedite ship set-up in the right location and orientation at the start of a CTD or other science station. They are frequently needed for washing ice chunks clear of the operating hole around the Baltic Room. There will also be conditions, possibly frequent, when ship handling requires significant thruster work on-station in ice.  Weak winds, where ice motion can be driven by ocean currents (e.g., tides) acting against the windage on the ship, is one example of conditions where maintaining position relative to the port-side ice could be difficult.  In open water, dynamic positioning (“DP”) as we used in the Mertz Polynya, requires continuous thruster work.  As a general rule, however, thrusters (especially the bow thruster) should be at the minimum setting (preferably even off) required to carry out CTD operations from the Baltic Room once the ship is positioned on-station.

Influence of thrusters and main engine wash on upper-ocean turbulence

The influence of thrusters on surface turbulence is apparent when watching the water around the Baltic Room door while on-station for CTD and other operations. Under high thruster power, the wash extends at least several tens of meters away from the ship. To what depth does this ship-driven turbulence penetrate? And: How important is this turbulence to upper-ocean data quality?

During AnSlope 3 we deployed a new instrument, the Vertical Microstructure Profiler (VMP; a.k.a. “Vampire”).  Vampire measures temperature, conductivity and ocean velocity fluctuations at very fine scales (~1-3 cm), and is used to calculate profiles of ocean turbulence.  Backscatter intensity on the ship’s acoustic systems (ADCP, and EK‑500 on previous cruises) is also found to be high over depth ranges where we expect turbulence.  Vampire and acoustic measurements both indicate that thrusters create significant mixing in the upper ocean.  If there is no near-surface stratification, i.e., a pre-existing deep mixed layer, the thruster-driven mixing extends to 50-100 m below the surface. This distance is estimated from turbulence measurements where there is no obvious geophysical source of upper-ocean turbulence such as wind stress, or convection due to surface cooling and ice formation.

Physical oceanographic process studies focusing on upper-ocean mixing have previously been carried out from Palmer by ship-supported “mini-ice-camps”, placing science huts over hydroholes cut through the ice some distance (~100 m) from the ship (the “AnzFlux” program in the eastern Weddell Sea in austral winter 1994).  However, the goal in AnzFlux was primarily to get away from more subtle wake effects due to flow under and around the hull, which might be expected to reach to about 20 m (roughly twice the draft).  It is clear from AnSlope 3 measurements that the thrusters extend the apparent ocean turbulence well below this depth.  One unresolved question is whether this on-station ship-induced mixing influences the data obtained from the CTD and water samples from the CTD rosette.  On a short station, deep thruster-induced mixing might only be found when the surface layer is well mixed already, i.e., where there is no pre-ship stratification to damp out turbulence. On stations where ice/ship drift is rapid compared with the underlying water, the thruster wash mixing downwards might not be seen since the water immediately below the ship is replenished by lateral relative motion.  However, on longer stations with little ice/ship drift relative to the ocean, continual use of thrusters may create upper ocean mixing and stratification conditions, which are not typical of the pre-ship environment.  This is especially important for near-surface bottle sampling from the CTD rosette, which takes place as the CTD is retrieved, i.e., after the ship has been on station for some time.

As with performance of the ship acoustic systems, the general conclusion of these studies is that, after station set-up and while the ship is on-station, thrusters should be at the minimum setting (preferably even off) required to maintain satisfactory ship motion and safety for the science taking place, whether CTD, Vampire, or other sampling.

[Laurie Padman]

 

2.12 Oceanographic conditions in northern iceberg field near 57.5oS

On the final transit of AnSlope 3, north from the Ross Sea towards Lyttelton NZ, we passed a field of icebergs centered near 57.5oS, 176.9oE. This was about 500 miles north of the sea-ice edge at this time.  The field included two large tabular bergs as well as many smaller, less regular-shaped bergs (Figure 23). Sea surface temperature (SST) and salinity (SSSal) both declined within the field (Figure 24), being significantly lower (by ~3o and 0.8 psu) than the surrounding values for about 0.5 h (~5 nautical miles at 10 knots). A sonobuoy deployed within the field by Sarah Dolman will be analyzed for evidence of anomalous marine life concentration, and the sounds of iceberg melt and fracturing.

XBT profiles taken through the field (Figure 25) confirm the reduction in SST seen in the underway data. These profiles show the icebergs to be located in an irregular transition zone between cooler upper-ocean (above ~300 m depth) water to the south and warmer water north.  In the profile taken within the iceberg field (T-7#347; green), the layer of cooled, fresh water (presumably a result of iceberg melting), is only ~20 m thick.  The deeper portion of this profile shows 3 cold intrusions, near 210, 390, and 450 m. While the origin of these intrusions is unknown, at least the ~210 m intrusion may be the result of lateral spreading of melt-water from the icebergs’ base.

From underway “Ocean Surveyor” ADCP currents (Figure 24), the iceberg field is coincident with a strong (~0.4 m/s) eastward-flowing current. Sea surface fluorometer readings (SSFluoro; Figure 24d) were low in a latitude band about 200 km wide, encompassing the “jet”. The complexity of upper-ocean temperature and currents suggests that frontal meanders or eddies may play a role in the advection of this iceberg field (and perhaps in keeping the group together). [Laurie Padman]


Figure 23:  Examples of icebergs seen near 57.5oS, 176.9oE. There were many tabular bergs (bottom) in the cluster. small, irregular bergs (top), and 2 large tabular bergs (bottom) in the cluster.

 
 

 

 



 


Figure 24 Time series of (a) latitude, (b) sea surface temperature (SST), (b) sea surface salinity (SSSal), (d) sea surface fluorometry (in volts), and (e) E/W (red) and N/S (blue) currents averaged over the top 300 m from the Ocean Surveyor 38 kHz narrow-band ADCP system. The center of the iceberg field is near t=337.9 days.


Figure 25 Profiles of temperature from T-7 XBTs south (profiles 345 and 346) of, within (347) and north (348, 349) of the iceberg field.  Each profile is offset from the previous one by 1oC. There are strong lateral gradients of T below the mixed layer, especially above 300 m between #345 and #346. The SST anomaly is confined to the upper 20 m. The surface layer in the iceberg field is cooler (and fresher) than the deeper water, while the surface layer north and south of the field is warmer than the underlying water.

 

 

 


 

 

3 Station Maps and Tables

 

3.1 Station Maps

 

 

Text Box: Figure A.1.  CTD station locations for the first leg of Anslope-3 off the George V Coast  Bathymetry from BEDMAP [Lythe et al., 2000], which is inaccurate in many locations, coastline approximate.  
Lythe, M.B., Vaughan, D.G. and the BEDMAP CONSORTIUM, 2000, BEDMAP - bed topography of the Antarctic. 1:10,000,000 scale map. BAS (Misc) 9. Cambridge, British Antarctic Survey.

Text Box: Figure A.2.  CTD station locations for the second leg of Anslope-3 in the Ross Sea.  Bathymetry from F. Davey compilations (2004), Institute of Geological and Nuclear Sciences.

 


3.2 CTD/LADCP Stations

 

 

   CTD

Latitude

Longitude

 

 

Date

M / D / Y

 

Time (GMT)

Max. Pres (db)

Water Samples

(No. of Rossette bottles sampled)

Deg

Min

Deg

Min

CFC

He

O2

3H

18O

Sal

Nut

1

46

2.057

171

55.641

E

10/13/04

06:19

1350

18

-

22

-

-

23

23

2

64

36.414

147

36.276

E

10/20/04

00:54

3620

22

-

12

-

6

23

22

3

65

42.295

147

17.88

E

10/20/04

18:25

2777

21

4

10

4

4

9

21

4

65

50.575

147

20.557

E

10/20/04

23:47

1997

16

3

14

4

3

15

17

5

65

52.908

147

15.508

E

10/21/04

03:17

1398

12

-

12

-

-

12

12

6

65

54.288

147

12.388

E

10/21/04

05:29

951

12

4

8

4

4

8

12

7

65

56.401

147

8.168

E

10/21/04

08:21

464

8

-

9

-

-

5

9

8

66

0.528

146

51.064

E

10/21/04

11:17

300

4

2

4

2

2

4

4

9

66

4.891

146

24.949

E

10/21/04

13:59

268

4

-

4

-

2

4

5

10

65

57.18

146

16.685

E

10/21/04

16:11

512

6

-

7

-

3

6

7

11

65

52.639

146

16.169

E

10/21/04

18:15

1040

7

-

7

-

-

5

7

12

65

50.298

146

16.511

E

10/21/04

19:57

1700

12

-

12

-

-

9

12

13

65

56.008

146

16.572

E

10/21/04

23:21

557

2

-

2

-

-

2

2

14

65

55.807

146

16.384

E

10/21/04

23:54

559

-

-

-

-

-

-

-

15

65

53.497

146

15.989

E

10/22/04

01:26

852

3

-

3

-

-

3

3

16

65

53.308

146

15.83

E

10/22/04

02:10

896

2

-

2

-

-

2

2

17

65

53.122

146

15.756

E

10/22/04

02:56

936

2

-

4

-

-

4

4

18

65

47.016

146

16.273

E

10/22/04

05:14

2215

12

-

8

-

4

6

12

19

65

41.611

146

16.336

E

10/22/04

09:05

2412

12

-

12

-

1

12

12

20

65

41.393

145

25.644

E

10/22/04

18:05

2886

12

-

12

-

-

9

12

21

65

50.144

145

25.343

E

10/22/04

22:47

2497

12

-

8

-

-

8

9

22

65

54.58

145

22.669

E

10/23/04

01:60

1347

7

-

8

-

-

5

8

23

65

55.591

145

21.288

E

10/23/04

03:56

986

8

-

6

-

-

6

8

24

65

58.973

145

20.048

E

10/23/04

06:04

408

6

-

6

-

-

6

6

25

65

55.549

145

5.342

E

10/23/04

08:47

1119

5

-

5

-

-

2

5

26

65

55.307

145

4.722

E

10/23/04

09:49

1281

4

-

4

-

-

3

4

27

65

57.421

144

49.566

E

10/23/04

13:22

797

7

-

7

-

-

5

7

28

65

54.889

144

34.328

E

10/23/04

16:12

1059

9

-

9

-

-

7

9

29

65

53.788

144

16.271

E

10/23/04

19:22

808

6

-

6

-

-

4

6

30

65

51.4

144

1.13

E

10/23/04

21:28

1051

8

-

8

-

-

4

8

31

65

48.866

143

44.225

E

10/23/04

23:48

1067

6

-

6

-

-

4

7

32

65

48.61

143

43.661

E

10/24/04

00:44

1136

3

-

3

-

-

2

3

33

65

48.427

143

43.151

E

10/24/04

01:39

1195

8

-

8

-

-

8

8

34

65

48.854

143

29.803

E

10/24/04

05:03

809

6

-

6

-

-

4

6

35

65

46.89

143

12.274

E

10/24/04

08:07

1095

5

-

5

-

-

5

5

36

65

48.094

142

56.454

E

10/24/04

11:38

1142

8

-

8

-

-

6

8

37

65

45.732

142

39.633

E

10/24/04

15:12

1233

8

-

7

-

-

5

8

38

65

46.938

142

36.205

E

10/24/04

18:06

835

5

-

5

-

-

4

5

39

66

1.75

144

34.526

E

10/26/04

12:04

316

4

-

4

-

-

3

4

40

65

56.012

144

34.33

E

10/26/04

14:36

710

5

-

5

-

-

4

5

41

65

53.931

144

31.722

E

10/26/04

16:47

1352

8

-

8

-

-

5

8

42

65

51.99

144

31.389

E

10/26/04

20:12

2039

13

-

8

-

-

6

13

43

65

47.52

144

26.764

E

10/26/04

23:25

2530

13

-

13

-

-

13

13

44

65

33.017

143

41.569

E

10/27/04

05:17

2140

9

3

6

3

1

4

10

45

65

45.295

143

43.888

E

10/27/04

09:45

1876

10

-

6

-

-

5

10

46

65

48.05

143

45.85

E

10/27/04

12:32

1406

9

-

5

-

-

5

9

47

65

48.691

143

45.244

E

10/27/04

14:39

1124

8

-

5

-

-

4

8

48

65

49.638

143

43.296

E

10/27/04

17:35

737

6

-

5

-

-

2

6

49

65

52.522

143

44.298

E

10/27/04

19:07

389

5

-

4

-

-

4

5

50

66

1.415

143

35.318

E

10/27/04

21:42

420

6

-

4

-

-

4

6

51

66

9.299

143

28.437

E

10/27/04

23:47

511

6

-

6

-

-

5

6

52

66

17.062

143

20.446

E

10/28/04

02:06

639

6

-

6

-

-

6

6

53

66

25.292

143

12.914

E

10/28/04

04:29

736

6

-

3

-

-

3

6

54

66

34.148

143

4.546

E

10/28/04

07:07

838

4

-

4

-

-

4

4

55

66

37.85

143

29.846

E

10/28/04

09:41

780

4

-

3

-

-

4

4

56

66

42.2

143

56.614

E

10/28/04

12:38

874

4

-

3

-

-

3

4

57

66

48.245

144

19.862

E

10/28/04

16:10

967

5

-

4

-

5

5

5

58

67

3.341

145

10.562

E

10/28/04

21:34

1305

8

3

5

3

5

5

8

59

67

6.882

144

54.608

E

10/29/04

00:26

510

8

5

7

5

5

7

7

60

66

54.979

145

28.859

E

10/29/04

10:58

662

6

-

4

-

-

-

6

61

66

47.45

145

44.881

E

10/29/04

13:07

454

6

-

4

-

-

5

6

62

66

39.895

145

58.989

E

10/29/04

15:37

302

5

-

4

-

-

4

5

63

66

29.987

146

20.67

E

10/29/04

18:13

233

3

-

3

-

-

3

3

64

66

19.745

146

14.252

E

10/29/04

20:17

241

4

-

4

-

-

3

4

65

66

30.09

145

48.125

E

10/29/04

23:09

222

4

-

4

-

-

4

4

66

66

40.013

145

23.83

E

10/30/04

01:34

465

12

-

6

-

-

6

6

67

66

31.253

144

53.706

E

10/30/04

04:39

441

6

-

6

-

-

6

6

68

66

22.282

144

24.396

E

10/30/04

07:46

456

6

-

6

-

-

6

6

69

66

12.373

143

56.926

E

10/30/04

10:33

427

7

-

5

-

-

5

7

70

66

3.011

143

28.51

E

10/30/04

13:44

462

6

-

4

-

-

4

6

71

65

55.156

142

59.827

E

10/30/04

17:09

422

5

-

4

-

-

4

5

72

65

50.08

142

54.991

E

10/30/04

19:19

668

6

3

4

3

2

3

6

73

65

49.243

142

54.245

E

10/30/04

20:58

902

9

2

7

2

2

5

9

74

65

48.403

142

52.903

E

10/30/04

22:47

1212

12

2

8

2

2

7

12

75

65

47.44

142

52.018

E

10/31/04

00:44

1494

10

-

6

-

-

6

10

76

65

45.452

142

48.845

E

10/31/04

02:56

1773

8

2

7

2

2

6

8

77

65

40.136

142

49.555

E

10/31/04

05:39

2105

8

1

5

1

1

5

8

78

65

31.004

142

53.285

E

10/31/04

09:17

2459

9

1

5

1

1

1

9

79

65

14.656

143

0.652

E

10/31/04

14:32

3083

11

-

6

-

-

6

11

80

54

17.735

166

20.334

E

11/4/04

01:15

1204

8

-

8

-

-

12

8

81

64

1.746

178

12.214

E

11/12/04

21:54

1051

12

-

8

-

1

8

12

82

65

0.124

177

53.435

E

11/13/04

07:51

1025

12

-

6

-

1

6

12

83

65

59.935

177

53.038

E

11/13/04

18:29

3561

12

1

7

1

1

7

12

84

67

0.332

177

44.509

E

11/14/04

08:31

1158

12

-

10

-

1

10

12

85

67

59.322

177

54.97

E

11/14/04

21:53

3538

24

-

14

-

1

13

24

86

68

56.935

175

56.412

E

11/15/04

14:42

1000

8

-

5

-

2

5

8

87

70

2.492

172

14.776

E

11/16/04

18:32

2606

12

-

7

-

2

7

12

88

70

21.709

170

30.428

E

11/17/04

10:05

2670

12

-

6

-

3

6

12

89

70

10.468

169

2.221

E

11/18/04

05:17

1009

-

-

-

-

-

-

-

90

70

9.992

168

59.93

E

11/18/04

06:08

1000

-

-

-

-

-

-

-

91

70

9.523

168

57.854

E

11/18/04

06:56

2546

12

-

8

-

-

8

12

92

71

31.441

171

36.887

E

11/20/04

09:32

475

12

-

8

-

2

8

12

93

71

27.125

172

0.206

E

11/20/04

11:36

776

8

-

5

-

2

5

8

94

71

27.08

172

4.985

E

11/20/04

13:09

1356

10

-

6

-

5

6

10

95

71

26.405

172

9.085

E

11/20/04

15:10

1647

8

-

5

-

3

5

8

96

71

25.073

172

21.139

E

11/20/04

17:44

1896

11

-

6

-

3

7

11

97

71

22.277

172

38.822

E

11/20/04

20:52

2229

12

-

7

-

3

7

12

98

71

57.004

171

34.315

E

11/21/04

03:48

373

6

-

6

-

-

4

5

99

71

55.36

171

50.033

E

11/21/04

05:16

533

6

-

5

-

-

4

6

100

71

53.639

172

12.732

E

11/21/04

07:32

1115

8

-

6

-

-

6

9

101

71

52.99

172

16.762

E

11/21/04

09:06

1337

9

-

6

-

-

6

9

102

71

50.741

172

49.291

E

11/21/04

12:17

1900

9

-

6

-

-

6

9

103

71

55.921

172

44.584

E

11/21/04

15:23

1699

6

-

4

-

-

4

6

104

71

57.82

172

42.51

E

11/21/04

17:19

1180

8

-

5

-

3

5

8

105

71

59.214

172

37.528

E

11/21/04

18:58

791

5

-

4

-

-

4

5

106

72

1.024

172

38.6

E

11/21/04

20:17

531

6

-

4

-

-

4

6

107

72

15.82

172

25.895

E

11/22/04

00:15

493

8

-

6

-

-

6

8

108

72

6.342

173

38.437

E

11/22/04

05:28

760

6

-

6

-

-

6

6

109

72

2.903

173

46.52

E

11/22/04

07:18

1206

6

-

5

-

-

5

6

110

71

58.681

173

44.564

E

11/22/04

09:22

1636

12

-

6

-

-

7

12

111

72

24.488

173

36.505

E

11/23/04

23:57

477

23

-

17

-

2

17

23

112

73

7.682

176

14.502

E

11/24/04

10:31

376

1

-

1

-

-

1

1

113

73

7.822

176

14.686

E

11/24/04

10:55

377

8

-

5

-

2

4

8

114

73

2.88

176

36.233

E

11/24/04

12:58

598

7

-

4

-

-

4

7

115

72

58.757

176

48.097

E

11/24/04

14:45

947

6

-

4

-

-

4

6

116

72

51.341

177

10.774

E

11/24/04

17:42

1302

7

-

4

-

-

4

7

117

73

25.998

177

7.294

E

11/25/04

01:26

549

9

-

6

-

-

6

9

118

73

39.376

176

12.5

E

11/25/04

05:28

597

10

-

5

-

-

7

10

119

73

54.523

177

15.536

E

11/25/04

10:07

408

9

-

7

-

-

7

9

120

74

54.379

179

30.350

W

11/26/04

01:37

491

8

-

6

-

-

6

8

121

75

23.881

178

32.116

W

11/26/04

07:26

512

11

3

6

3

5

6

11

122

75

12.254

177

29.962

W

11/26/04

10:57

568

3

1

3

1

1

3

3

123

75

12.302

177

30.731

W

11/26/04

11:33

567

7

2

4

2

5

4

7

124

75

8.178

177

36.007

W

11/26/04

12:58

783

8

2

5

2

6

5

8

125

75

6.082

177

43.228

W

11/26/04

14:31

1155

4

-

3

-

2

3

4

126

75

5.591

177

43.238

W

11/26/04

15:31

1230

8

-

5

-

2

5

8

127

75

1.342

177

51.795

W

11/26/04

17:21

1720

11

-

6

-

3

6

11

128

74

31.327

177

12.509

W

11/27/04

00:16

897

10

3

8

3

4

6

10

129

74

16.267

177

16.936

W

11/27/04

08:56

824

9

-

6

-

3

6

9

130

74

9.786

177

32.365

W

11/27/04

11:10

960

9

-

6

-

4

6

9

131

74

3.96

177

49.202

W

11/27/04

13:28

1529

9

-

5

-

3

5

9

132

73

58.816

177

57.864

W

11/27/04

16:58

2115

8

-

5

-

4

4

8

133

73

48.539

176

16.484

W

11/27/04

20:08

2568

20

-

11

-

4

11

20

134

73

9.01

177

41.595

W

11/28/04

04:26

2123

9

-

6

-

-

6

9

135

73

5.604

177

37.551

W

11/28/04

07:06

1545

9

-

6

-

-

6

9

136

73

0.802

177

37.519

W

11/28/04

09:32

1095

11

-

6

-

-

6

11

137

72

42.082

177

26.729

W

11/28/04

14:14

842

9

-

7

-

3

7

11

138

72

11.221

177

4.357

W

11/28/04

20:05

720

6

-

4

-

3

4

6

139

71

48.436

176

2.557

W

11/29/04

02:43

1116

11

-

6

-

-

6

11

140

71

24.476

179

21.339

W

11/29/04

08:22

1719

8

-

6

-

-

6

8

141

70

34.481

178

13.801

W

11/29/04

19:18

2772

10

-

7

-

1

6

10

142

69

40.916

178

9.530

W

11/30/04

07:20

3856

19

-

11

-

2

11

19

Total

1175

48

861

48

147

814

1181


 

Table A-1 CTD station locations and samples collected.
3.3 NBP04-08 LADCP Profile Quality

 


CTD/

LADCP

Reliability

Of results

Problem

 

CTD/

LADCP

Reliability

Of results

Problem

1

High

 

 

93

High

 

2

Low

Magn. Pole, bad beam

 

94

High

 

3

Medium

Magn. Pole, broken beam

 

95

High

 

4

Medium

Magn. Pole, broken beam

 

96

High

 

5

Medium

Magn. Pole, broken beam

 

97

High

 

6

Medium

Magn. Pole, broken beam

 

98

High

 

7

Medium

Magn. Pole, broken beam

 

99

High

 

8

Medium

Magn. Pole, broken beam

 

100

High

 

9

Low

Magn. Pole, broken beam

 

101

High

 

10

Medium

Magn. Pole, broken beam

 

102

High

 

11

Medium

Magn. Pole, broken beam

 

103

High

 

12

Low

Magn. Pole, broken beam

 

104

High

 

49

Low

Magn. Pole, 1 ADCP

 

105

High

 

50

Low

Magn. Pole

 

106

High

 

51

Low

Magn. Pole

 

107

High

 

52

Low

Magn. Pole

 

108

High

 

53

Low

Magn. Pole

 

109

High

 

54

Low

Magn. Pole

 

110

High

 

55

Low

Magn. Pole

 

111

High

 

56

Low

Magn. Pole

 

112

High

 

57

Low

Magn. Pole

 

113

High

 

58

Medium

Magn. Pole

 

114

High

 

65

Low

Magn. Pole

 

115

High

 

66

Low

Magn. Pole

 

116

High

 

67

Low

Magn. Pole

 

117

High

 

68

Low

Magn. Pole

 

118

High

 

69

Low

Magn. Pole

 

119

High

 

70

Low

Magn. Pole

 

120

High

 

71

Low

Magn. Pole

 

121

High

 

72

Low

Magn. Pole

 

122

High

 

73

Low

Magn. Pole

 

123

High

 

74

Low

Magn. Pole