Arctic Thaw: Measuring Change

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The Arctic is changing with a rapidity that has amazed scientists. The Greenland ice sheet is shrinking, sending over 48 cubic miles a year of ice streaming into the oceans, while Arctic sea ice cover continues to track below average. These changes will have significant effects regionally and globally. Scientists from Columbia University’s Lamont-Doherty Earth Observatory are flying over the region on a NASA-led mission called Operation IceBridge to understand what is happening on and below the ice.
Updated: 13 min 10 sec ago

Welcoming a New Instrument for ‘Probing’ the Polar Regions

Thu, 01/24/2013 - 14:30

The new Common Science Support Pod (CSSP) Ice Imaging System for Monitoring Changing Ice Sheets (IcePod), designed by Lamont’s Polar Geophysics Group (Image M. Turrin).

In 2009 it was just a dream. But creative vision, sweat equity, good partnerships and funding can bring dreams to reality, and 2013 delivered.

It was four years ago that a small team of Lamont scientists, Polar Geophysicist Robin Bell, Engineer Nick Frearson and Ocean Climate Physicist Chris Zappa, began discussions of an instrument that could be used to collect measurements on polar ice during routine field-support flights in both the Arctic and Antarctic. Named the IcePod, it would fit onto the LC130 aircraft, a massive four-engine turboprop plane that is the workhorse of the U.S. polar support services. The pod design focused on a 9 foot long cylindrical “boot” that would hold a range of instruments and gather data on ice conditions as the aircraft carried out its seasonal polar mission. The pod would be removable, fitting in the rear paratroop door, and modular allowing for a range of instruments and ultimate utility.

New York Air National Guard directing the landing of the large LC130 aircraft, backbone of the flight support for NSF polar science. (image courtesy of NYANG)

Funding came through special Recovery Act Funding of a National Science Foundation Major Research Instrumentation grant. NSF saw this as an opportunity for the full science community to increase data collection and understanding of polar ice conditions, yet with a significant reduction in the logistical support needed.

The polar flights for the LC130 are coordinated through NSF but flown by the New York Air National Guard, requiring close planning and coordination with both groups as the Icepod was developed. Any design would need to meet full air safety standards, cause limited drag on the aircraft and be easily mounted or removed by the air-crew as needed.

(l-r) Nick Frearson (Lamont Engineer), Capt. Josh Hicks (NYANG pilot) and Bernie Gallagher (Lamont Senior Electrical Technician) review the interior mount of the removable door where the IcePod will be installed in the LC130 (Image M. Turrin)

Panel openings in the side of the IcePod instrument show two of the equipment boxes. There is an additional box between these two that remains covered in this photo, as well as space in the nose and tail caps of the pod. (Image M. Turrin)

The instruments housed in and around the pod would need to be insulated from any interference with the plane and its equipment. Additionally as the pod arm is extended below the aircraft, the instruments would need to be tightly sealed for temperature control and able to pass intense turbulence testing. Calling up visions of the electromagnetic shrinking machine from “Honey I shrunk the kids,” an additional challenge was the need to fit the instruments in the small interior cubicles of the pod. Instruments and equipment were compacted and streamlined.

The starting line up of instruments:

Radar (RAdio Detection And Ranging) uses radio waves to image through the ice. In order to collect both deep and shallow ice information Icepod will carry two types of radar. Deep-Ice Radar (DICE) is a blade antenna resembling black shark fins designed to collect data thorough more than 4 km (resolution of 10 m). The DICE radar antenna will work over the deep interior of the ice sheets to measure ice thickness and bed wetness where water may be lubricating the base of the ice sheet and changing conditions. The Shallow-Ice radar (SIR) is a horn antenna for penetrating closer to the surface of the icesheet, through approximately 300 meters of snow (25 cm resolution). SIR focuses on recent processes in the snow/ice system, looking at annual rates of snow accumulation and the layer of snow (firn layer) not yet compressed into glacial ice, estimated to range in depth from 40-100 m below the surface.

Two blade antenna for the Deep Ice Radar extend from the pod. (Image R. Bell)

Optics: Laser, is an instrument that uses light to image and collect data on surface elevation and snow texture.  Two different cameras will be used to collect data on reflectivity and temperature (visible-wave and infrared cameras). As we layer together all the information collected from the instruments we can integrate our understanding of the ice conditions at the base of the ice sheet up through the internal ice layers, to the ice sheet surface, and up to the reflective return from the ice.

Next week the Lamont’s Polar Geophysics Team will fly with the New York Air National Guard, bringing the long envisioned IcePod into the air for field-testing. The team is excited to take to the skies to see what the instruments can do, although with the first battery of tests flown close to home in upstate New York, not all the instruments can be performance tested. If all goes well and the go-aheads are received, a trip to Greenland is planned for later in the spring to allow full instrument testing in true polar conditions.

To learn more about the Icepod project see: http://www.ldeo.columbia.edu/icepod/

For more on the Polar Geophysics Group: http://www.ldeo.columbia.edu/polar-geophysics-group/

Funding for this project from #ANT 0958658 under the MRI initiative.

The Art of Flying

Wed, 05/30/2012 - 14:50

Flying. It is something we are almost all familiar with, and yet I expect few of us have really sat back to appreciate the actual science of it. For the past 10 weeks we have been flying, not just a day or two a week but five or six days a week depending on the crew numbers and the weather options. We have worked out of two different locations in Greenland, both of which are on the western edge of this expansive island in the north.

View from the hill down on Thule Airbase. The hangars are the large buildings on the left. The control tower is visible between the hangars. The flat ice to the far right is the sea ice of North Star Bay.

For the past three weeks, we’ve been in Thule, Greenland. This US Air Force base has the northernmost paved runway in the region, offering service to points north (Yes, there are points north! ……. but those have gravel runways). The infrastructure here is good, complete with individual hotel rooms, as compared with the shared dormitory style rooms in Kangerlussuaq. Perhaps the most important part is that we get fresh vegetables with meals in the cafeteria. The lack of fresh vegetables for most of Greenland is remarkable as there really is no agriculture except a small amount of musk ox and reindeer (caribou) ranching. The Greenland diet is heavily slanted toward protein – fish and the meat of musk ox and reindeer.

The P3 is a workhorse of the Operation IceBridge field season. One thing that I’ve noticed, and had previously not appreciated, is that the blades of the propellers rotate. OK, before you say, “I knew that!” or, “No duh!” Take a look at the following photos. In the first photo in the hangar, the blades face the camera. The flat part is rotated towards the viewer. If you look closely, you can even see the point at which they are mounted.

Airplane propeller blades in the hanger.

Now, compare these with pictures taken from inside the plane. These are rotated to allow the propeller to push more air past the wing and increase speed – 90 degrees from the above picture.

Devon Ice Cap Mission over northern Canada. Notice how the propeller blade is rotated 90 degrees to the previous photo.

Cape Alexander flight with a calving glacier in the background. Again, the blades of the propeller have rotated on the black metal fairing.

This next video shows what you would observe of the propeller if you were inside the plane — just the gray windmilling of the propellers accompanied by a very loud buzz and whirr.  This will also give you a view of how we move through the vast snow covered landscape.  All of the missions are timed with respect to a ground speed of 250 knots for our instrument function (that’s 250 nautical miles per hour or about 288 miles per hour).

Click here to view the embedded video.


Part of the maintenance of the plane is a preflight inspection by the crew prior to any of the science crew or pilots arriving at the plane. This starts about 2 ½ hours before take off. Basic functions, such as checking the lights, seeing if the tail moves, etc. are all done prior to take off. When we do the night shift for firewatch, the shift ends as the crew arrives, so we are able to see the start of the inspection.
Additionally, the crew does an evening inspection of everything. Because the P3 is a workhorse of the NASA airborne science fleet, they keep the plane flying. The result is that parts wear out from time-to-time. The ground crew needs a little down time, and they get it during flight. Generally, they rotate off shifts with at least two always at the watch. Those who aren’t on watch take some down time — playing computer games or getting a few zzz’s in.

Crew down time in the plane.

The last few days have been a bit of an overdose on Thule Air Base, however. The flight crew found something in a post flight inspection. A bushing delaminated in the propeller.

Here is the engine on the far left side of the plane. Notice that the black fairing is removed. It is also a great photo for seeing that the blades are rotated relative to the neighboring propeller.

A view inside the engine of the P3. In the hangar, depending on the maintenance schedule, the doors commonly are left open.

With the bushing gone the first thought was to fly the P3 back to the Wallops Island, VA test flight facility using three engines. Once there, with the parts, tools, and ground support, they could fix the plane. After considering the number of completed flights it was decided to close the season. The P3 stayed in Thule with the parts expected to arrive on Monday during the regular resupply of the base from the US. Monday came and went with no parts. The C130 air transport plane from McGuire AFB was full and could not take the 600lbs of parts and tools. Option B was for the parts to arrive today on the rotator. The rotator is a DC-8 plane that is about a 2/3 supply shipment and about 1/3 passengers for any staff changes for any position at the base.

Luckily, the parts and tools arrived. The crew went straight to work. As I wrote this, the crew took off and landed with the P3 on an FCF: functional check flight. This is a test to make sure that everything works. Good times! I’m waiting for the report on what they found……..

The ‘Glory’ in Clouds and Other Amazing Sights!

Thu, 05/24/2012 - 15:04

If you look carefully at the picture below you will see a small shadow of our plane completely encircled in a rainbow. This optical phenomenon, called a “glory,” can develop when the plane flies directly between the sun and a cloud below. Flying over the ice sheet in the far northeast of Greenland we saw this “glory,” the result of refracted water in the clouds appearing like a rainbow-colored halo when the observer is directly between the sun and cloud of refracting water droplets. Because our ATM laser and the DMS cameras rely on there being no clouds beneath us as they collect data, we don’t often see “glories.” The light cloud cover seen here doesn’t bother the instruments much – we can still see through it – so we get data and “glory” – a win-win situation.

The optical phenomenon called a "glory" can develop when the plane flies directly between the sun and a cloud below.

The rocks peeking up through the misty cloud layer show evidence of fluvial drainage, where running water has cut through the rock. We have seen lots of evidence of running water in the north, both here and in the large, long drainage channels that ran over the surface of Humboldt Glacier in the northwest. Beneath these channels the geology in this northeast section of Greenland shows a more complicated relationship than we have seen elsewhere. Here we see alternating bands of lighter and darker brown in the rock face, unlike the more regular rock bedding we have seen in other regions.
Humboldt

Icebridge flew the Humboldt glacier for the first time this season. Humboldt, a very wide but slow-moving and slow-changing glacier, lies just to the west of Petermann Glacier at the very northern edge of Greenland. Most of the ice flow in Humboldt glacier is concentrated on its eastern margin, but the very wide calving front is very impressive.

Surface meltwater channels on Humboldt Glacier – this is just inland of the calving front – you can make out icebergs in the sea ice in front of the glacier at the top of the frame.

The eastern margin of Humboldt Glacier: Again you can see the icebergs out to sea. The scalloped edge marks the eastern boundary between rock and ice, and the rocks here are the same metasediments (sedimentary rocks that have experienced some metamorphism) that we see exposed in the cliffs on the margins of Petermann Glacier, which we have flown for the last two years, but didn’t get to this year.

Humboldt Glacier: You can see the very slightly dipping strata exposed in the side of this channel carved into the rock just off the side of Humboldt.

NW fjords
The northwest fjords flight was designed for the gravity team to survey just offshore, measuring the gravity signal of the sea bed to determine the geometry of the fjords. This information will assist modelers in investigating why the loss of ice mass in the area is increasing, and how ocean current might be involved.

Kong Oscar Glacier with all the ice and icebergs that have broken off floating in front. This broken ice debris in front of a glacier is called mélange.

We flew another mission in this area along the NW glaciers, flying up and down the axis of a dozen glaciers in this area to look at the bed structure with radar and changes in elevation over time using the ATM laser.

I got interested in the erosive power of the glaciers looking at sediment deposits coming off the valley walls. Sediment piles up at the bottom of cliffs

Sediment that piles up at the mouth of valleys has a delta-like appearance.

Glacial "trim line" shows where the glacier has been in the past.

Ellesmere Island
For the Ellesmere Island flight, I sat in the cockpit and we had a bit of everything. Ellesmere Island is the northernmost island in the Canadian Arctic, lying just west of Greenland in the Territory of Nunavut (Inuit for “our land”). The island is known as the home of the furthest north permanently inhabited place on Earth, Alert.

Beautiful clouds seen as we transited over Ellesmere Island.

I enjoyed this glacier because it appears to be sticking its tongue out as the ice has retreated up the valley wall over time.

And then exposed rock showing the variability of rock type in the area.

I was glad to have been on this flight, because it turned out to be our last one of the season (there were 43 data flights in total this year). Routine maintenance on the plane when we got back turned up a part that needed to be replaced, and the logistics of that are taking time. So we are waiting in Thule for the part to get here (there are only a couple of flights a week that it can come on). Once everything is operational again, we will be heading home. We’ve packed our cargo, backed up all the data, and now we are catching up on blogs and reports and all the desk work that wasn’t done on the plane. The current plan is to fly home on Friday – contingent on the part arriving on Thursday and everything going perfectly from there. In the meantime, I can look out the window and see fox and hare tracks in the snow.

Our Best Flight Yet

Wed, 05/09/2012 - 16:07

Southwest Glaciers Flight plan. Tasermuit Fjord is at the southern tip of Greenland, and the town of Narsarsuaq far up the fjord.

Evidence of the retreat of glaciers since the last glacial maximum (check), flying over sites of ancient Inuit, Norse and present day settlements (check), and a personal recollection of my own past in this location (check) – yes after reviewing the list ‘Southwest Glaciers 01′ was definitely the best flight – well at least until the next one!

In 1997 I got to spend a summer in Southwest Greenland, with the organization British Schools Exploring Society (BSES). They bring students at the end of high school/start of university to remote areas to spend six weeks on a combination of adventure and science – a great way to kick start a young adult into both a career path and self-discovery. I spent my time in Tasermuit fjord, a 70 km long stretch of water reaching inland from Greenland’s southwestern tip to the ice cap, and bounded by steep ridges the tallest standing over 2000 meters high. I learned about archeology and botany and developed a taste for field science that led fairly directly to my studying geology at university. Fifteens years later that study has brought me back around to Tasermuit fjord, this time having swapped my backpack and Zodiac inflatable boat for a rather large gravimeter and the P3 aeroplane. Tasermuit fjord looks exactly the same. I imagine I do too.

Site of the 'British Schools Exploring Society' 1997 Greenland basecamp on the shores of Tasermuit fjord. (K. Tinto)

The SW Glaciers mission brought me past the site of my 1997 basecamp….and also right past the mouth of the spectacular valley I spent several rainy days walking through. The valley is called Klosterdalen, and the mountain on the right hand is Ketil – a name associated, I am sure, with the Ketilidian orogeny that deformed these rocks in the Paleozoic some 2000–1750 Ma. Norse history would tell us that Ketil was one of Eric the Red’s men, and this was where he chose to settle. While Ketil himself postdated the orogenic event, in one of life’s ironies it appears all those million years later Ketil was responsible for the name given the orogeny and the resulting mountain. Of course the local Greenlandic have their own name for the mountain, Uiluit Qaqa, or “Oyster Mountain”, perhaps for the banks of mussel that become visible at low tide.

The valley of Klosterdalen with Ketil mountain rising to its height of 2010 m in on the right side of the image. (K. Tinto)

These pictures put a human scale on Greenland for me, because I know intimately how it feels to walk through the valleys. It is also a part of Greenland with a very clear human history, with physical evidence of both Inuit and Viking settlements in this region, including the ruins of a Norse settlement at the head of Klosterdalen.

Just around the corner (in our plane anyway – it took about a week to travel by fishing boats when I was here the first time) was the town of Narsarsuaq – an airport town, the site of an old US base and also very close to Erik the Red’s dwelling, the first Norse settlement in Greenland.

So we had some human history, and some personal history, but then we got some glacial history too, showing the retreat of the Greenland glacier from the last glacial maximum. Greenland glaciers offer some classic images of the processes we find described in textbooks.

The U-shaped valley filled with a fjord shows the classical shape of a valley carved by a glacier. (K. Tinto)

The terminal moraines in this picture (the mounds of sediment in front of the ice) show points where the glacier has paused in its retreat, sediments picked up in the moving ice during its advance are piled up at its terminus. (K. Tinto)

A hanging valley, where ice has poured from a smaller tributary into the main glacier when the ice was higher. (K. Tinto)

The dark lines of sediment within this glacier are medial moraines – when small glaciers converge – debris from their sides (lateral moraines) converge, and are carried along within the larger glacier. (K. Tinto)

The contrast in rock colour on this photo shows a 'trim line' marking how high the ice was (and was depositing debris on its sides) in the past. (K. Tinto)

So all in all it was a great flight. Evidence of the retreat of glaciers since the last glacial maximum, flying over sites of ancient Inuit, Norse and present day settlements, and some personal recollections. I would be grounded for the next week by night shifts, but these too were not without some fine sights.

Snow on the P3 during night watch of the gravimeter - you can just pick out the indicator light flickering in the window showing that the gravimeter is staying warm. (K. Tinto)

Clearing snow off the P3 wings in the morning before taking flight. (K. Tinto)

Our last sunrise in Kangerlussuaq – we won’t be seeing another of these, since now we have moved up to Thule and the sun won’t set again until we return to Wallops at the end of the season. (K. Tinto)

Clues to Sea Level Rise Are Hidden In and Below Greenland’s Ice

Sun, 04/29/2012 - 16:54

One of Greenland's many outlet glaciers moves ice from the land into the ocean. (Photo M. Turrin)

The charge is simple – Operation Ice Bridge will fly all 200 Greenland outlet glaciers with an end dimension of over 2 km. The reason? These outlet glaciers (fast moving ice bounded by mountains) are the major mechanism carrying ice off this mega-island and into the surrounding ocean. Greenland is surrounded by a ring of high mountains that work like fingers encircling the ice to hold it in place. Between these mountain ‘fingers’ ice slips through in streaming rivers transporting its frozen cargo to the sea. Ice sliding from the land into the surrounding waters results in a major human impact – Sea Level Rise.

Measuring the ice thickness (ATM, RaDAR), the shape and opening size of the land beneath the ice (RaDAR, gravity), and the type of geology (magnetics) will help with determining how much ice is on this northern land and to calculate how quickly it might move from land into the ocean. These 200 outlet glaciers are key to this calculation. Each flight mission covers a different group of glaciers, some repeating flights from earlier years to measure any change in ice elevation, and some new flights over glaciers never before measured in order to collect baseline data. In addition to flying the outlet glaciers each mission involves transit lines. Careful planning goes into laying out these lines in order to build a comprehensive ‘blueprint’ of Greenland’s land mass. Hidden under several kilometers of ice the land is slowly being pieced together with each line of data collected.

Screen shot of the MCoRDS radar screen. The right side shows mountains under the ice sheet (the tallest are ~ 1 km under the ice) (Photo M. Turrin)

Each instrument on the plane collects valuable information for the project, but with four types of RaDAR being collected this season most of the flights include at least one of these as a ‘priority instrument’. RaDAR, an acronym for radio detection and ranging, has been a part of our vocabulary and has enhanced our understanding of the world since the Second World War. Sending out radio waves and capturing their return has provided us information on ships, aircraft, missiles, weather formations, speeding motor vehicles and – the focus of this project – the terrain. Each of the RaDAR used in Ice Bridge has been designed by CReSIS (Center for Remote Sensing of Ice Sheets) with a unique frequency and penetration for a specific use, yet all have overlap or redundancy.

Sea Ice along Greenland's Eastern coast shows areas of thicker (white) and thinner ice (translucent) sliced through with open water leads (dark blue). CReSIS Ku band radar is used to measure fairly thin layers of snow accumulation on top of sea ice. (photo M. Turrin)

For detecting the very freshest snow the Ku band is important. Ku uses the highest frequency, 12-18 GHz, providing high-resolution information on the top 15 meters of snow cover, and has been used this season to separate the snow layer thickness on top of the sea ice when trying to determine overall ice thickness. The Snow RaDAR operates at 2-8 GHz and focuses on the top 30 meters of snow cover, often an area of unconsolidated ice (the firn layer), and an interim stage between snow and glacially compressed ice. Accumulation RaDAR operates at a lower resolution of 600-900 Mhz penetrating down a full km into the ice providing data on the internal layers of ice as they collect and move over the landforms. Lastly, the MCoRDS RaDAR is the priority for information on the bed shape beneath the ice sheet. MCoRDS uses a low frequency or 180-210 Mhz to penetrate down to 4 km beneath the ice surface giving us the depth and shape of land below, and any constrictions to ice flow.

The RaDAR can provide information on the shape of the land surface but not on the geology, and if there is water it can’t image through to see what lies below. This is where Lamont’s gravity and magnetics teams work to fill in the missing information. Matching the bed shape to the gravity/magnetics information on the ‘bed’ material is important in developing our understanding of how the glacier may move in the future.

One of Greenland's outlet glaciers shunts ice into the ocean. The edges of this icy chute are worn to a deep 'fluting'. (Photo M. Turrin)

Measuring Greenland’s ice sheet and the land that holds it in check is a first step in a long walk that will take us to predicting the future of that ice sheet and its impacts on sea level rise. Every line of Ice Bridge data collected fills a blank that moves us closer.

**************

Special thanks to Aqsa Patel & Kevin Player for their willingness to answer all my questions on the CReSIS radar systems, and Beth Burton and Kirsty Tinto on the magnetics and gravity systems.

For more blogs on this project: http://blogs.ei.columbia.edu/tag/greenland-ice-sheet/
For more on this project at LDEO: http://www.ldeo.columbia.edu/icebridge
For more about NASA Ice Bridge: http://www.nasa.gov/icebridge/

Midgard Glaciers hold the mark of Thor

Thu, 04/19/2012 - 14:08

Clouds hang above the Midgard glaciers like the fire from Thor's lightening bolts. (photo B. Burton)

To Norse mythology Midgard is a place that is impassable, surrounded by a world of ocean. Thor, the hammer-wielding warrior god often traveled across to Midgard, and one imagines evidence of his fiery power remains in the highly charged rocks that are left behind. Magnetized rocks containing Thor’s energy and the fiery touch of his lightning bolts.

We are soaring today 1500 ft. over the surface of the twisting branches of the Midgard glaciers. Patches of low lying clouds drape around the tops of the mountains, like smoke from Thor’s lightning singes, but as the sky opens we see row upon row of majestic peaks. It is hard to balance the icy cold of the Greenland exterior with the  molten heat of Thor’s lightning. Midgard, is cold and impassable, yet it is evident why Thor was attracted to this land.

Greenland’s geology is diverse. Some of the oldest rocks on Earth are found in southwestern Greenland in the Isua Greenstone Belt, an Archean belt between 3.7 and 3.8 billion years of age. Today, however, we are flying over the opposite side of the country.

Referred to as ‘Miss Greenland’ by K. Tinto, this large slash of intruded rock shows as a black sash running across the rocks of this coastal fjord. (Photo K. Tinto)

The Midgard glaciers hug the southeast of Greenland where the main rock is Archean gneiss, later reworked and cut through with a mafic, or iron rich, intrusion. Perhaps this occurred when Thor was traveling these peaks. We see the changes as spikes in our magnetic data, and visual features that appear as well.

The tail stinger houses the magnetometer on the back of the Ice Bridge P3. (photo K. Tinto)

Magnetic measurements are some of the many measurements being collected by Operation Ice Bridge. Rocks have different magnetic properties, so collecting magnetic data can tell us something about the type of rocks that are under the ice, assisting in refining our understanding of how the overlying ice will interact with what is below.

Beth Burton, U.S.G.S. works on the magnetic data during the flight. (photo M. Turrin)

Measuring the magnetic field can be challenging from a metal plane, however the P3 is designed for magnetic surveys so the data requires only a minimal ~10nT (nanoTeslas) adjustment to remove the interference.  Originally used by the Navy for locating submarines the P3 has a tail stinger or boom designed to hold the instrument while minimizing magnetic interference from the plane. The Ice Bridge P3 holds two magnetometers.  One measures the total magnetic field, the other is a flux gate, with three orthogonal sensors to record plane directional maneuvers, information that is needed for later data corrections.

Beth collects data from the magnetic ground station after the flight. (photo K. Tinto)

The Earth’s magnetic field is not constant so collecting data at a magnetic ground station is important in order to gather daily background levels. The magnetic anomaly that we report is the change from this background or anticipated levels.  This means that a series of corrections must be applied to all the data collected including removing the Earth’s total magnetic field, daily diurnal fluctuations, and small spikes from the plane radio. What remains is the anomaly, any representation of a magnetic signal from the geology in the area.

Section of Greenland’s magnetic anomaly map with circles highlighting our survey region. The boundary of Greenland is marked in black on the left of the screen with Iceland’s boundary showing on the right. Between the two countries new seafloor is created. You can see the episodic magnetic reversals like stripes marking each section of basaltic seafloor as it is created.

Magnetic surveys normally begin with an assessment or compensation flight in a magnetically quiet area, at a high elevation to minimize the effects of high magnetic gradients caused by the geology.  This provides the reference points needed for final corrections and processing of the data. This season Ice Bridge has had the opportunity to fly almost continuous missions so the compensation flight has been put on temporary hold. Once that flight is completed, the data will receive a final adjustment.

Two screen shots showing magnetic response. The sinuous data line marked on the left image shows the transition from a magnetic high to a magnetic low. When there is a distinct magnetic boundary with a high magnetic gradient, the values are changing at such a high rate that they appear as a block, as is noted in the second image. (Image by K. Tinto)

Today our screens are busy with magnetic shifts tracking on the screen. Seeing the data jump onto the screen is always exciting. The instruments take a reading approximately every meter as we fly above at a rate of close to120 meters a second. The data appears as a wrapping stream of plotted points.  When a line travels from one side of the left hand column to the other it shows that the magnetic field has changed by 100 nT.  The second column shows greater detail in the measured field with one line showing a change of 10 nT. Peak values of magnetic anomalies appear as a mid-column direction change on the wrapping plot. When the magnetic gradients are high, indicating a distinct geologic boundary, it can appear as a dark block.

What we see on the screen tells us about what happened in the geologic formation of this country millions of years ago. Understanding how the changing rock types affect the flow of ice can help us to predict what might happen in the future.

For more on this project at LDEO: http://www.ldeo.columbia.edu/icebridge

For more about NASA Ice Bridge: http://www.nasa.gov/icebridge/

Clouding our Image

Tue, 04/17/2012 - 18:42
East coast Greenland

The coast of Greenland by the Midgard glaciers as the sea fog mists through the air. (Photo M. Turrin)

Even in idyllic Greenland some days start to feel like the movie “Groundhog Day”, however the turn of events today broke that thread. Over our two weeks in Kangerlussuaq we have ended our evenings with a science and weather report, and the hope of flying the program over both coasts. Each morning we wake up, head to the plane and look to see what the weather has dealt us. So far with incredible consistency clouds have dictated a series of flights on the east coast of Greenland. Today started exactly the same with clouds on the west coast driving a plan to fly the centerlines of several large southeast glaciers – Helheim, Kangerdlugssuaq, and Midgard.

But today would not be like every other. We lifted into the air and immediately loud rattling emerged from under the plane. The belly of the P3 has been outfitted for science equipment and directly in the line of the rattle lie a series of elevation survey instruments – two Airborne Topographic Mapper (ATM) lasers, that send and receive a steady series of laser pulses, and two Digital Mapping System (DMS) cameras, that take high resolution surface images every 1.2 seconds. Both of these instruments are used to develop elevation maps of the area surveyed.

Three floor plates were quickly removed and a member of the aircrew is tethered for safety and dropped below. Looking down I could see straight through to the land and a surface dotted with small melt ponds. It seems you could put your hand straight through the bottom of the plane, but there is a surface – clear glass in two portholes and clear acrylic in the third. Each morning I have watched the ATM and DMS teams carefully clean these lenses to the outside world.

Looking through the floor window at James Jacobson cleaning the window for the DMS camera (photo M. Turrin)

After a quick review of the situation the decision is to return to the airstrip and attempt a repair, but first we must lighten the plane. Physics tells us that a fully fueled plane ready for a day of science work is not safe to land. Working with the air tower a place is selected to drop some fuel, we rise in elevation to minimize the impact of the drop, and then we are ready to cycle back to the base for a quick check.

The windows below the ATM and DMS are checked. They must be perfectly clear and there is spatter to be wiped away. A safety inspection and refueling puts us back on the runway taxiing in just over an hour. A warning light appears as we taxi and we aborted again. This time it is a quick fix and we are off and flying within thirty minutes – all in all a 2.5 hour delay which requires an amended mission. Helheim-Kangerdlugssuaq-The Sequel!

We will fly over water and glacial ice today giving both ATMs a work out. The primary system has a wider swath (700-800 ft.) working best over glacial ice. The secondary system has a narrower swath width with a smaller angle of incidence, the preferred system for sea ice. Sea ice has a mix of open water leads and thin sheets of ice making it difficult for the primary system to collect wide-angle measurements over both the ice and open water leads.

Image of an Iceberg in a mix of sea ice created using ATM data from Helheim glacier (generated by Matt Linkswiler of the ATM team)

As we begin the flight the secondary ATM needs adjustment. The laser pulse is sent out through a series of mirrors and collected back through a telescope that needs to be able to ‘see’ the laser return to measure the surface elevation. Once again the floor panel comes up, but the adjustment is a quick fix. The cold weather can be one cause of this drifting.

Low lying clouds and sea ice fog hang over the tops of the mountains along the fjords. (Photo M. Turrin)

As we reach the coastline it becomes apparent there is sea fog and wispy clouds laying low over the glacier and waterfront. The trouble with clouds or fog is they will block out both lasers unless we can get under them. In some places we can fly beneath the clouds, but in other areas it is not possible so we will lose some of the ATM data. It can’t be helped. Sea fog is extremely difficult to pick up on the synoptic charts used to assess the weather each day. We are lucky, however, and at the end of the day the ATM team reports 40 gigabytes of data collected. Little was lost to the clouds and fog.

Tomorrow we will need to wait and see if the cycle is broken, sending us to the west coast.

Midgard glacier coastline (Photo M. Turrin)