Table of Contents
The objectives of Palmer Cruise 97-5 is: 1. to set out the array of Dovetail moorings which is designed to monitor for a period of 8 to 16 months the highly variable circulation within the Weddell-Scotia-Confluence region; 2. to deploy drifters for monitoring of sea ice response to wind and the sea ice divergence; and 3. to investigate ocean thermohaline, oxygen, velocity profile and tracer chemistry stratification in the region separating the circumpolar water masses from those of the Weddell Gyre and intervening Weddell-Scotia Confluence. Of specific interest is: 1. the outflow of dense bottom water from the Weddell Sea; 2. the spill-over and spreading of dense Weddell waters across the South Scotia Ridge; and 3. nature of the winter mixed layer and its relationship to the pycnocline and WDW t-max. A more general objective of the Dovetail program is to establish a design for a cost effective, long term monitoring strategy for the bottom water outflow from the Weddell Sea and secular variability of water column stratification.
The observational program includes: CTD/Oxy and Lowered ADCP sensors; water samples for salinity, oxygen, nutrients, CFC, Tritium/Helium, stable isotopes; 12 moorings; 6 ice drifter. Besides basic navigation, the underway observations included hull ADCP, SeaBeam as required for mooring site survey, meteorological monitoring.
The packet of figures attached to this report shows the station positions, the mooring and drifter deployment sites, plus a selections of data displays.
A. Gordon, Chief Scientist
R. Muench Co-Chief Scientist
[A] CTD/Oxy/salinity/LADCP (midnight-noon)
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| B. Huber- Head | P. Mele- Head |
| J. de Bettencourt (LADCP) | M. Visbeck (LADCP; hull ADCP) |
| A. Orsi (salinity) | R. Iannuzzi |
| S. Green (Oxy, nutrient) | S. Ma (salinity) |
| S. Peacock (nutrient; Oxy) |
[B] Chemistry
[C] Mooring / Drifter:
[A] Palmer 97-05 Dovetail Project Status Report 1
Arnold L. Gordon, Chief Scientist, DOVETAIL
Friday, 8 August 1997; TIME: 1300 local (1700 Z)
LAT/LONG 60 deg 10'S; 44 deg 15' W starting CTD #15
Ship departed Punta Arenas around 3:10 PM local on 31 July. Moderate seas along a line from the eastern entrance to St. of Magellan to the first CTD station at 57.5 deg S and 45 deg W. From there worked our way south mostly along 44.5 deg W, with CTD stations, more closely spacing once south of 59.5 deg S to better resolve the northern front of the Weddell-Scotia Confluence and the deep waters in the deep trough north of the South Orkney Islands. First ice bands near 58.7 deg S. Full cover of ice south by 59.5 deg S. South winds have moved ice front northward, but generally thin, new ice, as we are in an ice shadow from the Orkneys. Thicker ice expected as we move southward east of the Orkneys.
Completed CTD #14 station at 60 deg S, 44.31 deg W. All CTD, LADCP operation and water sampling for chemistry and CTD calibration going fine, except for a problem with the oxygen titration unit. The data clearly define the strong isopycnal stirring of Weddell waters with Circumpolar water, as well as the spill-over of dense water from the Weddell into the southern Scotia Sea.
Mooring deployment ran into problems during the first attempted deployment at 58.7 deg S, 44.5 deg (anchor first method was used because of ice floes). It was aborted, and mooring site 2 deployment at 59.50 deg S, 44.40 deg W was postponed, as line handling and deployment methods had to be reconsidered. The modified deployment method (see ASA report for details) was applied with success at mooring site at 60 deg S and 44.31 deg W, which at 4800 m is the deepest of the Dovetail moorings. We will deploy the moorings at the first two sites later in cruise as we head west from the completion of the 40 deg W line. SeaBeam surveys of mooring site (all three sites were 'SeaBeamed') proceeding nicely, even in ice the SeaBeam views are useful in selection of exact site for deployment.
[B] E/mail problem: The following assessment was sent to ASA and NSF on 15 August:
"During first few days of the Palmer 97-5 cruise we were able to receive, but unable to send e-mail communications. This was corrected on 6 August, apparently there was a problem at the ASA Denver site. On 11 August our ability to send and receive e-mail ceased. Eventually we were able to receive mail, but not send. Finally on 14 August we transmitted messages via a Lamont server, which clearly demonstrated that the problem was again located at ASA Denver.
"E-mail communication is a cost effective link for cruise participants to the global internet. The ability to access e-mail is essential to the success of a scientific expedition: receipt of ice charts and weather helps steer the field program; exchange of technical and science information with the home office or colleagues maximizes the ability of on board scientists to exploit their field presence; exchange of official business keeps the scientists in touch with their many other commitments in a timely fashion; and, one should not underestimated the importance of personal e-mail exchange as an effective moral booster. I place reliable e-mail communications at very high priority. I'm not one of those that go to sea to get away from communications.
"I was very surprised to find that the Palmer e-mail services are not dependable. I thought by now ASA after supporting the science programs on Palmer for 5 years, would have worked out the best procedures to maintaining reliable e-mail communications. I officially voice my displeasure with the present situation and I strongly urge ASA to place Palmer e-mail services at the highest state of reliability as quickly as possible."
[C] Palmer 97-05 Dovetail Project Status Report 2
Robin Muench, Co-Chief Scientist, DOVETAIL
Friday, 15 August 1997; TIME: 1000 local (1400 Z)
LAT/LONG 64°15'S; 40°00' W, at CTD #32
Our DOVETAIL cruise is proceeding well and "on schedule". The ship is making reasonably good time through nearly total ice cover capped with several inches of new snow. The shipboard scientific equipment is operating well. We have now completed the first meridional CTD transect along about longitude 44 W across the plateau surrounding the South Orkney Islands. This transect veered eastward toward its southern end, culminating with cast #32 in the deep basin near 64.25 S. Nominal station spacing along this transect has been 10-15 n m, generally closer over the shelf and steep slope regions. A preliminary look at the data show the deep plume of Weddell Bottom Water paralleling isobaths deeper than about 3600 m. Additionally, we have identified a high oxygen, high CFC water mass near 1500 m on the southern slope of the South Orkney Plateau. This water mass, not seen before, is of uncertain origin. Additionally, the Weddell temperature maximum is significantly warmer than seen in the historical data. We are now preparing to jog eastward and commence a northward transect along about 40 W.
The lowered ADCP (LADCP) continues to provide invaluable results on the deep currents. These data show a significant near-bottom counterclockwise circulation around the South Orkney Plateau and around a smaller bank just north of the Plateau, and eastward near-bottom flow in the Bottom Water plume south of the Plateau. These results are being used to estimate the barotropic currents, and preliminary computations suggest large eastward volume transports in the northern Weddell that are consistent with published estimates of western boundary transport.
Four of the six Argos-tracked ice buoys have been deployed, to date, over a grid having length scales of order 100 km.
Finally, five of the 11 planned deep current moorings have been successfully deployed - all along the 44 W meridional transect. Moorings deployed were at sites 7, 8, 9, 11 and 12 (site 10 - a shallow site containing a single current meter, was deleted). The remaining two moorings along this transect - at sites 13 and 14 - will be deployed during the westward transit toward 48 W from the north end of the 40 W CTD transect. These deployments required design by shipboard ASA personnel of a hydraulic winch-based system by which the moorings can be spooled directly off the stern anchor first. This system has proven to be robust, relatively safe, and fast. A thorough pre-deployment check of the current meters has suggested that they are functioning per design and should yield high quality datasets. The earliest data returns are scheduled to begin on 1 March 1998 - the estimated time of greatest ice retreat.
[D] Palmer 97-05 Dovetail Project Status Report 3
Status Report of Palmer 97-05
Friday, 22 August 1997; TIME: 0900 local (1300 Z)
Enroute from 58°30'S, 40°W to the Dovetail mooring site at 59°00'S; 44°15'W
[A] Accomplishments:
We have completed two sections consisting of closely spaced stations along 44°W and 40°W between 58°S (average) and 64°20'S, they share a common southern station. A total of 50 stations have been obtained usually at 15 to 20 nm separation. The 44°W section crosses the South Orkney Plateau; the 40°W section crosses a gap in the South Scotia Ridge which channels the major overflow of dense Weddell Sea into the Scotia Sea. A station includes CTD, with Lower Acoustical Doppler Profiler (LADCP), water samples for salinity; oxygen; nutrient; CFC-11,12,113; Helium; Tritium; stable isotopes. Underway data includes navigation, hull ADCP, meteorology.
The two completed sections extend from the southern limits of the circumpolar regime into the Weddell Gyre. They provide an excellent view of the transitional fronts and zones between these regimes, including the Weddell-Scotia-Confluence, the outflow of dense bottom water from the western Weddell Sea and the interaction of the Weddell and Scotia Seas.
3. All six ice drifters have been deployed, all south of 62°S. They vary in separation from 80 to 150 km.
[B] Science topics:
1. Benthic layer of Weddell Sea Bottom Water (WSBW) is often thick, well mixed, other times thin and stratified. Some relationship to bottom topography is observed. However, as we sometimes see a mixed mode, there also may be a sporadic nature in that the well mixed benthic layer is formed locally and then lifted off the bottom by the surrounding, denser stratified layer. A series of such event would eventually mix all of the WSBW into the water column.
2. The effective depth of the 40°W controlling sill for Weddell overflow into Scotia Sea is 3150-3300 m, located near 60.5°S and 41.5W.
3. The Weddell Deep Water (WDW) t-max water sampled by the Dovetail sections is derived from the Weddell western boundary current. The WDW t-max is substantially warmer than observed in previous years. The t-max observed south of the Scotia Ridge is near 0.7°C, 0.15°C warmer than that measured by Palmer in 1992, and by earlier cruises to the region. Weddell Gyre t-max warming over the last 2 decades has also been reported for the area west of Maud Rise.
4. As mentioned in the last status report, the South Orkney Plateau bottom water (around 1000 m) consists of a well ventilate water mass, which either formed locally (unlikely) or spreads from the west 'floating' over a interval of denser water.
[C] Plans: After deployment of the two remaining moorings along 44°W we will head west to deploy the last 5 Dovetail moorings along 48.5°W. The station section along 48.5°W will extend across the Powell Basin. We will attempt to reach the position of the German moorings off Joinville Island, then into the eastern Bransfield Strait. The array of Dovetail stations will define the ocean stratification and velocity profiles along several slices of the Weddell-Scotia-Confluence, allowing inspection of the changing form of the fronts, zones and Weddell Sea outflow, as they cross the complex topography of the South Scotia Ridge.
[D] Comments:
1. The ship officers and crew, the ASA team and the science grantees are all performing in an excellent manner.
2. The e/mail problems seem to have been solved, as we are presently back to using Glacier ASA Denver server, with a commercial internet server as back up. We are following a twice daily e/mail exchange. While I am pleased that e/mail problems have been tended to, I would hope that a reliable e/mail service becomes the norm for all future cruises abroad Palmer.
Arnold L. Gordon...Friday, August 22, 1997
[E] Palmer 97-05 Dovetail Project Status Report 4
Robin D. Muench
Thursday, 28 August
The DOVETAIL cruise is progressing well.
We have completed 63 CTD/rosette/LADCP casts to date, and scientific systems are performing well. Our progress is being aided at present by favorable ice conditions, light winds and surface air temperatures near freezing. We are now working our way southward on a transect that extends along approximately 48 W starting at about 59.5 S, and are nearing the midpoint of the Powell Basin at about 62 S. Our course of action at the southern end of our present transect, near 63 S, will depend somewhat on local ice and weather conditions. Our plan is to work along a track from that point that extends west to Joinville Island thence north across Bransfield Strait, effectively closing a "box" that encompasses the source waters for the DOVETAIL study region.
Ten of the eleven planned moorings have been successfully deployed. Mooring 15, at the northern end of the 48 W transect, was attempted under less than ideal conditions of heavy swell passing through a rubble field. A particularly large sequence of swells parted the line when the mooring was about 70% deployed, causing the loss of one current meter, an anchor and some line. It was not feasible to wait for conditions to improve. The remaining components are being used to construct an additional mooring that we plan to deploy at the northeastern end of Bransfield Strait near the end of the cruise, allowing measurement of currents from the Strait into our study area.
Very preliminary analyses of results to date along the 48 W transect reflect the general conditions seen farther east. A cold, saline bottom water layer was present near 3000 m along the northern periphery of the Powell Basin. This provides evidence that at least some of the newly formed bottom water enters and circulates around the Basin rather than simply flowing eastward past its entrance farther south. Additionally, we have detected layers of cold, low salinity, high oxygen water between 1500-2500 m depths in the northern Powell Basin. These reflect input of shelf waters.
We continue to enjoy the Palmer's unique combination of Chilean, Philippine and Cajun cuisine, and are looking forward to new discoveries during the coming week.
[F] Palmer 97-05 Dovetail Project Status Report 5
Final Weekly Status Report of Palmer 97-05, DOVETAIL
Thursday, 4 September 1997; TIME: 1:30 PM local (1730 Z)
62°30'S; 57°47'W
Arnold L. Gordon, Chief Scientist
I first present my comments, then comments from various participants concerning their responsibilities.
[A] Accomplishments:
We have completed 94 stations (anticipate a total of 97 for the cruise, just beginning 95) stretching from the central basins of the Bransfield Straits eastward to 40°W, east of the South Orkney Islands. In the meridional the sections extend from the Circumpolar water column of the Scotia Sea across the Weddell-Scotia-Confluence, the outflow of Weddell Sea Bottom Water, into the interior regime of the Weddell Sea.
A station includes CTD, with Lower Acoustical Doppler Profiler (LADCP), water samples for salinity; oxygen; nutrient; CFC-11,12,113; Helium; Tritium; stable isotopes. Underway data includes navigation and bathymetry, hull ADCP, surface water temperature and salinity, meteorology. We deployed 11 current meter moorings and 6 satellite tracked sea ice drifters. The drifters were deployed south of 62°S along the 44W and 40W sections. Reports of the other programs are included below.
[B] The Science:
The Dovetail CTD/LADCP/Tracer data set is very extensive and a number of research topics pertaining to Weddell Sea forced ocean ventilation can be pursued. The primary topics and questions are:
• Warmer Weddell Deep Water t-max: The Weddell Deep Water warming of the last few decades, continues. This trend may result from decrease of deep water heat loss to the atmosphere and cryosphere or increase of injection of warm circumpolar deep water into the Weddell Gyre. What is the cause of the WDW warming? What is the relationship of the t-max warming to sea ice distribution, glacial ice melting, Weddell Sea Bottom Water production and to the Weddell Polynya?
• Benthic Layer: The Dovetail CTD/tracer data along with the 1992 Weddell Ice Station data set nicely define the stratification and spatial pattern of the Weddell Sea Bottom Water benthic layer in the western and northwestern Weddell Sea. The Dovetail LADCP provides a glimpse of the velocity field associated with the WSBW. The WSBW benthic layer takes on varied forms: thick well mixed layer; a thin stratified form. Often (mainly on the 40°W section) a more complex form appears with attributes of both types. What is the relationship of the Benthic layer type to the sea floor depth, slope and bottom roughness; to the water column temperature and salinity stratification and stability; and to LADCP measured bottom current and shears? What is the WSBW transport? What is the role of the Powell Basin in governing the downstream form of the Benthic layer? Does benthic mixing receive positive feedback from thermobaric effects?
• W-S-C Low Salinity Deep Water: Within the Weddell-Scotia-Confluence over the South Scotia Ridge west of the South Orkneys, there is a well ventilated low salinity deep water, which may be referred to as Weddell-Scotia-Confluence Deep Water. It advects eastward to provide the bottom water on the southern, deeper parts of the South Orkney Plateau and then passes northward into the Scotia Sea. The Dovetail data clearly shows it is coming from the Antarctic Peninsula eastern shelf. It may be considered as a less dense form of Weddell Sea Bottom Water. It rides the 'outer-rim' of the Weddell Gyre, to feed into the Weddell-Scotia-Confluence. The Weddell-Scotia-Confluence Deep Water spreads on density surfaces into the Powell Basin and Scotia Sea, over-riding the Weddell Sea Bottom Water and may influence the thickness of the benthic layer. How much Weddell-Scotia-Confluence deep water is formed? What is it's relationship to the formation of Weddell Sea Bottom Water? Where is the specific source of the low salinity shelf water? Is there a Larsen Ice Shelf contribution? and what is its role in larger scale ocean ventilation?
Concluding Remark: The western Weddell continental margins form freezing point water with a wide range of salinity that ventilate the neighboring ocean from the sea floor (southern Weddell Sea) to the pycnocline (Bransfield). This water then reaches into the deep and bottom layers of the global ocean.
[C] Plans: As of this time we still need to complete sampling within the Bransfield Strait, which I believe provides the pycnocline waters of the Weddell-Scotia Confluence. We also will determine the renewal of the trapped water in the deep basins, with the first modern tracer coverage in the Strait.
[D] Comments:
1. The ship officers and crew are excellent. They handled the ship very effectively in the ice. I particularly appreciated their positive attitude towards the frequent change of plans forced by the ice, weather and "real-time" disclosures in the data stream. The ASA team were invaluable, and also have that positive 'can-do' attitude towards their responsibilities. The science grantees are all performing in an excellent and cooperative manner.
2. Reliable e/mail is a real problem on Palmer, as discussed in previous e/mail exchange. Considering the importance of good communication the correction of this problem should be placed on high priority. Reliable e/mail service must become the norm for all future cruises abroad Palmer.
3. SeaBeam is a valuable tool for physical oceanographic research (in addition to MG&G). The detailed bottom bathymetry SeaBeam images are very helpful in the analysis of ocean stratification and currents. Even in the presence of sea ice (where the raw data looked hopeless) with heavy editing the SeaBeam data provide clear views of the sea floor. Because of contractual issues involving ASA and SeaBeam, on Dovetail we were limited in its use to survey of mooring sitings, these surveys proved to be very important. However, further use on Dovetail would have been an asset. The present SeaBeam system makes data editing very labor intensive. Whatever can be done to more streamline this process with computer assisted editing routines should be done. In view of the poor quality of Southern Ocean bathymetric maps, I recommend that SeaBeam data be obtained as routinely as possible on as many Palmer cruises as feasible. Speaking for physical oceanographic studies, detailed bathymetric data will also help re-analysis of archived data sets. Unless a more streamlined data editing procedure is developed the science party members should be advised that they will be asked (to volunteer) to help edit the data during the cruise.
4. Accurate information flow from ASA to the science grantees prior to the cruise should be improved. Besides an unexpected problem I encountered, I understand that there were minor misunderstandings, mostly to do with the Palmer computer facilities.
REPORTS:
--------------------------------------------------- Moorings Current Mooring Deployments Robin Muench (co-chief scientist)
Eleven arrays of moored current meters were deployed successfully during the cruise. Of these, ten were positioned as specified in the DOVETAIL proposal and one was repositioned based on field conditions. Nominal depths for current meters on the arrays are 200 m, 500 m and 50 m above the seafloor. Seven arrays were deployed along a meridional transect, coincident with the initial CTD transect of the cruise, crossing over the South Orkney Plateau near 44 W. Four moorings north of the Plateau will measure deep and bottom water flow in that part of the Scotia Sea expected to be impacted by Weddell Sea Bottom Water. Three moorings are situated south of the Plateau in locations optimal for measuring deep and bottom water flow in the northern Weddell Sea. Three additional arrays were deployed along a second meridional transect, also coincident with a CTD transect, along about 48 W. Two of these are located to measure flow in the vicinity of a gap in the South Orkney Plateau through which Weddell Sea water can flow, while the third is located to measure along-isobath flow near the base of the continental slope in the Powell Basin. The eleventh and final mooring was deployed partway down the western continental slope of the Powell Basin near 52 W, at the end of a short CTD transect that extended southeast into the Basin. CTD, bottle and LADCP data acquired at the site of each mooring deployment substantiated that most were situated in regions of particular interest with respect to deep and bottom water movement.
Deployment of the moorings proceeded, with one exception, exceedingly well and without untoward incident. The initially planned method, based on use of a brailing head, never worked because the head proved unusable for this purpose. An alternate deployment scheme was devised that used the seismic gun winch. This method proved to be relatively safe, trouble-free and rapid. One 3000-m deep mooring was deployed in less than 1-1/2 hours. The single mishap occurred in attempting to deploy a northernmost mooring along the 48 W transect. Conditions at the time were a broad swell passing through a rubble field. The rubble prevented an anchor-last deployment which would normally have been used in the presence of swell, and the mooring line parted upon passage of a particularly heavy set of swells with the mooring about 70% deployed. It was decided to use the remaining components to deploy a relocated mooring which was finally emplaced in Powell Basin at the site near 52 W. This very successful set of deployments could not have taken place without exceptional performances by ASA shipboard personnel, especially Rhonda Kelly, Mark Talkovich, Gary Osborne and Melissa Iszard-Crowley. These individuals designed the highly successful deployment method, spent many cold hours on deck and were extremely helpful, cooperative and pleasant during all phases of the operation.
The Palmer proved highly suitable for the mooring deployments. The heated fantail deck provided an excellent preparation area, and the stern A-frame and associated winches were more than up to the task.
Use of the SeaBeam system proved essential for the success of the deployments. A short survey, typically covering a 100 square kilometer region and requiring 3-4 hours time, was made of each site prior to the start of deployment. A target deployment site was then selected based on the detailed local bathymetry. Wind, ship and ice drift were assessed, and a scheme devised so that the ship could be at the site by the time the mooring was fully in the water and ready to be released. Many of the deployments occurred in areas of extremely steep and poorly charted bathymetry, and the ability to chart and plan the deployments proved crucial. Finally, thanks are due to Suzanne O'Hara, who spent long, irregular and uncomplaining hours operating the SeaBeam system and led a number of us cheerfully through the onerous process of editing the data.
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CTD, Computer and underway operations. Bruce Huber
CTD Operations: The package used during DOVETAIL consisted of an ASA SBE 9plus CTD with dual sensors, 24-position SBE Carousel water sampler with 10-liter bottles, a bottom pinger and bottom contact switch. The CTD cable is in excellent shape. The cable was already terminated when we boarded, and was not reterminated. A Lowered Acoustic Doppler Current Profiler (LADCP) was provided by Lamont. ASA support personnel mounted the LADCP components on the CTD frame using materials from both shipboard ASA stock and Lamont. The secondary CTD temperature sensor was found to be faulty during initial checkout of the CTD, and was replaced. Some minor adjustments were made to the sensor plumbing to improve flow.
After some initial minor problems with leaky bottles and recalcitrant carousel triggers, the water sampler performed very well with a minimum of trouble. Most annoying of these minor problems was the tendency for the endcap o-rings to become loose, sometimes resulting in lost samples. It appears that some of the end caps were not machined to close enough tolerances, resulting in sloppy o-ring fits. These should be relegated to the spares drawer, and replaced with endcaps with properly machined o-ring grooves.
Both conductivity sensors were replaced early in the cruise due to sediment fouling after impacting the bottom on station 2. ASA is to be applauded for maintaining an extensive stock of CTD sensors, most of which had been recently calibrated.
Lamont computer and peripheral equipment was used for the CTD data acquisition and some processing operations. The ASA support personnel were very helpful in rearranging existing computer equipment in order to meet our needs. Some of the shipboard CTD computer equipment is quite old and should be upgraded or replaced. Some of the monitors are so old the phosphors are dimmed to the point of causing eyestrain.
Over the side CTD operations were for the most part smooth, especially in the pack ice. In open water, with only moderate swell, operations are a bit dicey. A faster boom would reduce the risk to the package upon deployment and recovery in moderate to rough conditions.
Water samples were analyzed for dissolved oxygen and salinity. The shipboard salinometers were used for the latter analysis, and many problems were encountered. One unit, reportedly just returned from factory calibration, was found to be unusable. The other performs well as long as the ambient temperature doesn't fluctuate, and when there is minimal vibration due to ice breaking (which means not often working well on this cruise).
Oxygen titrations were initially done on a Lamont automated titrator. This unit eventually failed, and the ASA optical endpoint titrator was set up and used. There were only minor problems with this unit (including a cracked UV source lamp) and it has overall performed well. Again, thanks to the ASA support team for assistance. It should be noted that during the planning phase of DOVETAIL we had requested the ASA titrator be made available as a spare, so proper planning paid off.
Computer support and underway data logging: The ASA computer support personnel were very helpful in getting us set up, including putting some of our computers on the network. Equipment was moved when necessary, and every effort was made to give us what we needed within the constraints of the systems installed. Email is not so great and should be completely revamped. In fact, the entire network of networks should be reevaluated and streamlined. The concept is great, but there are surely better ways now to implement multi-platform networks. The underway data collection system is a great idea too, but the implementation requires too much maintenance. The meteorological display is unreliable - the data should be median filtered before averaging to avoid contamination by serious outliers and gps flake-outs. The TSG appears to be working well, even in the ice, in welcome contrast to earlier experiences.
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Lowered Doppler Current Profiler (LADCP), Martin Visbeck
The goal of this project was to obtain top to bottom velocity profiles by using two ADCPs attached to the CTD frame. The LADCP-2 system was recently developed by the PI and this cruise was the first scientific application of the new system. I staged the LADCP operation in the dry lab next to the Baltic room. The ASA staff help during the setup phase and designed an efficient mounting system using parts that I brought along. Two RDI WH-150 ADCPs and one battery pack were mounted on the CTD frame, one ADCP looking upward and the other one downward.
We were able to operate the LADCP system at every station.
The procedure was fairly simple and required no extra station time. The ASA team helped to set the data logging and data processing computer system up. Once everything was running we were able to provide full ocean depth velocity profiles about 15-30 minutes after the CTD was on board. The quality of the data set was very good and interesting scientific conclusions could already be drawn. To my knowledge this was the first extensive survey of near bottom currents in the Weddell-Scotia confluence zone.
This project would have benefited from more SeaBeam data throughout the cruise. Bottom currents are obviously directly affected by the bathymetry and the charts available are insufficient to say the least. To me it seemed that we have wasted an opportunity to improve on the quality of bathymetric maps by not using a sounding system which could have been available.
Overall we have demonstrated that the LADCP system has great scientific payoff for a minimal extra investment and should be part of the standard hydrographic package. Aside from the at times terrible e-mail situation I want to thank the captains and crew of the N.B. Palmer and the ASA support team for making this cruise a worthwhile operation.
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Tracer Chemistry Manfred Mensch
Tracer Sampling (D. Breger, L. Breger, B. Gordon, G. Mathieu, S. Mathieu, M. Mensch)
Tracer samples were collected to supplement the information derived from the standard hydrographic parameters temperature, salinity and dissolved oxygen.
CFC samples (PI W.M. Smethie) were taken at all stations and with very few exceptions at all depths where Niskins were tripped. The analyses were performed within less than 12 hours of the sampling. Frequently, air samples were analyzed to establish the atmospheric CFC concentrations. They will be used to calculate the CFC saturation of the surface waters.
Helium, oxygen isotopes and tritium samples (PI P. Schlosser) were collected at about every third station. The samples will be shipped back to Lamont-Doherty Earth Observatory where they will be processed at the Noble Gas and Stable Isotopes Laboratories.
The water sampling package used during the cruise performed very well. No mistrips were encountered and the total number of leaky Niskins was very small. At the beginning of the cruise, all O-Rings on the Niskins were replaced with BUNA-N O-rings that were baked under vacuum at 80°C for one week to minimize the danger of CFC sample contamination. Unfortunately, the test and shake down station did not sample CFC free waters so that the blank levels of the Niskins could not be established. Replicate samples that were frequently drawn throughout the cruise do not exhibit any suspicious variability. Therefore, we are confident that the Niskins did not contaminate the CFC samples.
The ASA personnel on board as well as ECO's officers and crew members provided excellent support. All our requests and needs were answered in a prompt and friendly manner. We were very pleased with their expertise, efficiency and cooperation that helped making our part of the cruise a great success.
As is my normal policy, any Dovetail researchers or member of the Palmer 97-5 science staff can receive preliminary forms of the data obtained during the cruise. However, it must be recognized that the data are in preliminary form and are released only as an aid in interpretation of the specific data program of the Dovetail researcher or as an educational tool. The data set is not to be shared by people outside of the Dovetail program.
For each data set there is an "owner". Use of data for science analysis requires approval of the "owner". "Ownership" expires two years after the end date of the cruise or in the case of mooring and drifter data, two years after the data are recovered from the field.
I assume all of this is clear, but a more subtle point is as follows: if one uses the data for a routine procedure that would have been done by the "owner", that does not buy collaboration (co-authorship). "Owners" invite collaboration.
OWNER DATA SETS: CTD (Gordon); bottle: salinity (Gordon), oxygen (Gordon), nutrient (Peacock), CFC (Mensch/Smethie), Trit/He (Schlosser), stable isotope (Schlosser); LADCP (Visbeck); eventual data from moorings (Muench) and drifters (Martinson).
GROUP DATA SETS: Navigation; weather; hull ADCP; underway T and S; bottom bathymetry; SeaBeam at survey sites.
As the "Owner" of the CTD and associated bottle data, I make plots available to Dovetail researchers and Palmer 97-5 science staff. A. L. Gordon
V CTD List; Dovetail Mooring and Drifter Deployment Sites:
• CTD
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8/4/97 | 12:01 | 57 | 30.070 | S | 44 | 59.468 | W |
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test station. | ||
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2 |
8/4/97 | 18:02 | 57 | 59.994 | S | 44 | 30.180 | W |
2781 |
hit bottom at 30m/min | ||
|
3 |
8/4/97 | 22:26 | 58 | 21.096 | S | 44 | 30.462 | W |
2801 |
primary co sensor changed before this station | ||
|
4 |
8/5/97 | 11:08 | 58 | 42.975 | S | 40 | 30.097 | W |
2431 |
large ice floes in belts and strips | ||
|
5 |
8/6/97 | 00:29 | 59 | 05.820 | S | 44 | 29.754 | W |
1208 |
|||
|
6 |
8/6/97 | 09:14 | 59 | 30.660 | S | 44 | 22.810 | W |
2211 |
40 m off bottom | ||
|
7 |
8/6/97 | 14:48 | 59 | 45.510 | S | 44 | 21.120 | W |
4406 |
|||
|
8 |
8/6/97 | 19:41 | 59 | 53.369 | S | 44 | 20.206 | W |
4727 |
|||
|
9 |
8/7/97 | 00:52 | 60 | 04.192 | S | 44 | 17.647 | W |
4821 |
|||
|
10 |
8/7/97 | 04:49 | 60 | 07.800 | S | 44 | 16.540 | W |
5088 |
|||
|
11 |
8/7/97 | 09:59 | 60 | 07.795 | S | 43 | 53.865 | W |
4771 |
|||
|
12 |
8/7/97 | 15:11 | 60 | 07.455 | S | 43 | 30.977 | W |
4994 |
|||
|
13 |
8/7/97 | 22:05 | 60 | 03.612 | S | 43 | 59.442 | W |
4962 |
no bottles | ||
|
14 |
8/8/97 | 03:37 | 60 | 00.223 | S | 44 | 18.631 | W |
4819 |
mooring site 12 | ||
|
15 |
8/8/97 | 17:08 | 60 | 10.800 | S | 44 | 15.216 | W |
5326 |
|||
|
16 |
8/8/97 | 22:39 | 60 | 19.902 | S | 44 | 00.214 | W |
4626 |
sensor chg co 2nd | ||
|
17 |
8/9/97 | 07:05 | 60 | 28.920 | S | 44 | 11.760 | W |
1489 |
mooring site 11 | ||
|
18 |
8/9/97 | 18:43 | 60 | 56.929 | S | 44 | 07.333 | W |
246 |
6 bottles | ||
|
19 |
8/9/97 | 23:08 | 61 | 11.520 | S | 44 | 02.939 | W |
376 |
6 bottles | ||
|
20 |
8/10/97 | 07:56 | 61 | 33.226 | S | 43 | 59.397 | W |
519 |
near mooring 9 | ||
|
21 |
8/10/97 | 22:51 | 61 | 59.228 | S | 43 | 55.891 | W |
912 |
|||
|
22 |
8/11/97 | 05:58 | 62 | 16.800 | S | 43 | 38.360 | W |
1171 |
|||
|
23 |
8/11/97 | 11:09 | 62 | 26.460 | S | 43 | 20.878 | W |
1450 |
mooring site 8 | ||
|
24 |
8/11/97 | 20:40 | 62 | 40.216 | S | 43 | 11.077 | W |
3237 |
|||
|
25 |
8/12/97 | 04:48 | 62 | 49.375 | S | 42 | 55.637 | W |
3463 |
ice buoy | ||
|
26 |
8/12/97 | 14:50 | 63 | 00.559 | S | 42 | 32.291 | W |
3743 |
mooring 7 | ||
|
27 |
8/13/97 | 12:09 | 63 | 09.975 | S | 42 | 07.127 | W |
3757 |
|||
|
28 |
8/13/97 | 21:11 | 63 | 22.873 | S | 42 | 01.656 | W |
3796 |
near possible small seamount | ||
|
29 |
8/14/97 | 03:20 | 63 | 31.378 | S | 41 | 47.094 | W |
4560 |
near site of UK mooring | ||
|
30 |
8/14/97 | 13:57 | 63 | 50.203 | S | 41 | 01.134 | W |
4501 |
Ice Buoy | ||
|
31 |
8/15/97 | 00:51 | 64 | 04.871 | S | 40 | 25.066 | W |
4628 |
|||
|
32 |
8/15/97 | 11:05 | 64 | 16.017 | S | 39 | 59.650 | W |
4703 |
ice buoy w/ thermistor | ||
|
33 |
8/16/97 | 02:05 | 63 | 50.161 | S | 40 | 07.846 | W |
4623 |
|||
|
34 |
8/16/97 | 14:10 | 63 | 05.060 | S | 40 | 02.474 | W |
4228 |
|||
|
35 |
8/17/97 | 02:06 | 63 | 13.475 | S | 40 | 04.628 | W |
4371 |
Ice Buoy | ||
|
36 |
8/17/97 | 19:41 | 62 | 55.547 | S | 40 | 02.848 | W |
4286 |
rough bottom | ||
|
37 |
8/18/97 | 02:52 | 62 | 35.856 | S | 40 | 08.074 | W |
2695 |
|||
|
38 |
8/18/97 | 08:32 | 62 | 20.047 | S | 40 | 02.252 | W |
3354 |
Ice Buoy | ||
|
39 |
8/18/97 | 15:20 | 61 | 59.525 | S | 40 | 07.770 | W |
3377 |
|||
|
40 |
8/18/97 | 22:33 | 61 | 44.454 | S | 40 | 03.497 | W |
3421 |
|||
|
41 |
8/19/97 | 09:40 | 61 | 25.084 | S | 39 | 56.356 | W |
3190 |
|||
|
42 |
8/19/97 | 19:54 | 61 | 11.142 | S | 40 | 04.194 | W |
2775 |
|||
|
43 |
8/20/97 | 00:55 | 61 | 08.788 | S | 39 | 43.520 | W |
2852 |
|||
|
44 |
8/20/97 | 05:25 | 60 | 59.977 | S | 39 | 30.271 | W |
4021 |
|||
|
45 |
8/20/97 | 13:18 | 60 | 42.119 | S | 40 | 01.039 | W |
5449 |
Orkney Deep | ||
|
46 |
8/20/97 | 22:21 | 60 | 18.007 | S | 39 | 59.435 | W |
1331 |
|||
|
47 |
8/21/97 | 05:17 | 59 | 53.490 | S | 39 | 58.244 | W |
1618 |
|||
|
48 |
8/21/97 | 11:40 | 59 | 29.839 | S | 39 | 59.453 | W |
1909 |
|||
|
49 |
8/21/97 | 17:31 | 58 | 59.827 | S | 40 | 00.092 | W |
2341 |
|||
|
50 |
8/22/97 | 00:41 | 58 | 28.986 | S | 40 | 00.697 | W |
3353 |
station aborted due to high wind, seas and ice | ||
|
51 |
8/23/97 | 02:12 | 58 | 38.272 | S | 44 | 32.334 | W |
2931 |
Mooring site 1 (m14) | ||
|
52 |
8/23/97 | 13:41 | 59 | 30.696 | S | 44 | 24.444 | W |
2255 |
Mooring site 2 (#13) | ||
|
53 |
8/25/97 | 01:10 | 59 | 48.960 | S | 48 | 13.458 | W |
4362 |
|||
|
54 |
8/25/97 | 07:45 | 59 | 59.856 | S | 48 | 14.920 | W |
4386 |
|||
|
55 |
8/25/97 | 19:14 | 60 | 17.468 | S | 48 | 15.647 | W |
5280 |
near mooring 10 (#16) | ||
|
56 |
8/26/97 | 02:16 | 60 | 30.085 | S | 48 | 04.762 | W |
1358 |
|||
|
57 |
8/25/97 | 10:30 | 60 | 33.026 | S | 48 | 17.208 | W |
1968 |
mooring 12 (#17) | ||
|
58 |
8/27/97 | 03:57 | 60 | 44.970 | S | 48 | 19.554 | W |
2481 |
|||
|
59 |
8/27/97 | 10:38 | 61 | 02.090 | S | 48 | 19.252 | W |
2759 |
|||
|
60 |
8/27/97 | 20:27 | 61 | 18.410 | S | 48 | 18.034 | W |
2876 |
|||
|
61 |
8/28/97 | 02:46 | 61 | 30.000 | S | 48 | 32.400 | W |
3084 |
|||
|
62 |
8/28/97 | 09:05 | 61 | 44.965 | S | 48 | 41.713 | W |
3255 |
|||
|
63 |
8/28/97 | 15:42 | 61 | 59.844 | S | 48 | 59.034 | W |
3317 |
|||
|
64 |
8/28/97 | 21:47 | 62 | 14.779 | S | 49 | 14.438 | W |
3347 |
|||
|
65 |
8/29/97 | 04:04 | 62 | 30.160 | S | 49 | 22.153 | W |
3386 |
|||
|
66 |
8/29/97 | 13:03 | 62 | 46.470 | S | 49 | 41.255 | W |
3398 |
|||
|
67 |
8/29/97 | 18:15 | 62 | 56.221 | S | 49 | 54.029 | W |
3409 |
|||
|
68 |
8/29/97 | 22:48 | 63 | 04.580 | S | 50 | 00.348 | W |
2660 |
|||
|
69 |
8/30/97 | 11:08 | 63 | 04.776 | S | 50 | 40.614 | W |
1519 |
|||
|
70 |
8/30/97 | 18:11 | 63 | 05.814 | S | 51 | 29.382 | W |
1581 |
|||
|
71 |
8/31/97 | 01:28 | 63 | 03.676 | S | 52 | 09.293 | W |
550 |
|||
|
72 |
8/31/97 | 06:34 | 63 | 05.900 | S | 52 | 54.094 | W |
444 |
|||
|
73 |
8/31/97 | 10:40 | 63 | 06.193 | S | 53 | 37.199 | W |
323 |
|||
|
74 |
8/31/97 | 14:06 | 63 | 05.650 | S | 54 | 18.070 | W |
395 |
|||
|
75 |
8/31/97 | 18:46 | 63 | 06.047 | S | 54 | 59.830 | W |
511 |
Near Joinville Is. | ||
|
76 |
8/31/97 | 22:15 | 62 | 47.933 | S | 54 | 50.716 | W |
179 |
|||
|
77 |
9/1/97 | 01:33 | 62 | 29.946 | S | 54 | 45.229 | W |
275 |
|||
|
78 |
9/1/97 | 04:16 | 62 | 17.916 | S | 54 | 35.983 | W |
529 |
|||
|
79 |
9/1/97 | 06:48 | 62 | 09.077 | S | 54 | 23.740 | W |
803 |
|||
|
80 |
9/1/97 | 09:43 | 61 | 59.923 | S | 54 | 14.850 | W |
578 |
|||
|
81 |
9/1/97 | 12:10 | 61 | 44.556 | S | 54 | 06.870 | W |
344 |
|||
|
82 |
9/1/97 | 15:28 | 61 | 31.470 | S | 54 | 02.106 | W |
918 |
|||
|
83 |
9/1/97 | 20:00 | 61 | 14.504 | S | 53 | 50.623 | W |
1319 |
|||
|
84 |
9/2/97 | 00:39 | 60 | 53.926 | S | 53 | 30.180 | W |
663 |
|||
|
85 |
9/2/97 | 03:20 | 61 | 04.498 | S | 53 | 20.644 | W |
1902 |
|||
|
86 |
9/2/97 | 21:46 | 61 | 39.790 | S | 51 | 59.662 | W |
2170 |
near mooring site | ||
|
87 |
9/3/97 | 04:48 | 61 | 39.104 | S | 52 | 30.016 | W |
471 |
|||