Arctic Thaw: Measuring Change

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 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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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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/

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.

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.

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.

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.

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.

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.

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/

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.

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.

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.

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.

I had been warned of Geikie.  “If they fly to Geikie get on that flight” I had been told, but nothing more. At the science briefing last night I knew it was a possibility, but daily science missions are not decided in the confines of a meeting room. Missions are decided by weather, and its weather that drives the transit today forcing us up over the clouds. A snowy air mass has descended upon Kangarlussuaq extending back over the icecap, leaving an opened window over the Geikie Peninsula.

The transit will be high putting many of the instruments out of their range.  The Laser altimeter, visual camera and gravity all become a casualty at higher elevation, yet the magnetics and radar continue to collect data during the commute. But the story today is not in the transit, it is in the small jut of rugged cut coastline in Southeast Greenland called the Geikie Peninsula. An elongated ice plateau at more than 6500 ft. of elevation, Geikie is the northern end of a section of steep flood basalts that flowed out like the upward sweep of a hook.

Geikie is both a challenging target, and a bit of an enigma to the science team.  Geikie is a hard area to study because of its location.  It is the furthest target from any air bases in Greenland and in Iceland, and it is located just at the lip of the weather systems moving in from the Icelandic Low. A notorious herald of foul weather, the Icelandic Low dominates this section of the Southeast Greenland coastline.  Pulling warm water from the oceans into the atmosphere between the two ice blocks of Iceland and Greenland, the Icelandic Low contributes to nearly constant bad flight weather in this part of Greenland. Along with being a difficult target the small glaciers we will fly today are surging or dynamic glaciers. Surging glaciers are difficult to fully understand and account for in models. We hope to collect data that will help define the bed beneath the ice in these dynamic glaciers. In order to do this we will fly right down the trunks of eight of Geikie’s glaciers.

When the peaks of Geikie appeared from the snow I was captivated. Line after line, row after row pyramid like peaks rose with a certain regal proudness through the ice sheet.  Chiseled points with finely leveled layers stood 1500 ft. and higher through the ice, surrounding the plane, while below us the radar showed the ice thickness to be 1.5 miles.  These are towering features.  Buried millions of years ago by the ice sheet this truly must be Greenland’s hidden treasure.  Sheared edges formed perfect pyramids where competing ice flows had crossed, working in opposition to carve away the rock.  Regal gateways of perfectly opposing pedestals of rock showed the promise of rock formation after rock formation through the opening. Large crouching shapes appeared trailing down to rounded blocks of rock emerging like the toes of an Egyptian sphinx standing guard over this magnificent treasure for all these years.

We collect measurement after measurement, image after image as we soared by the guardians of Greenland. While we collected almost two terabytes of data we did not disturb their slumber. We left Geikie as we found it, frozen, vast and arresting. If they fly to Geikie, get on that flight!

Over 100,000 years of Arctic climate data has been linked in the last two days of Ice Bridge missions. When you see the names DYE2, EGIG, GRIP, Ice Bridge and MABEL you view the elite list of Arctic science projects that deliver(ed) groundbreaking climate information through the last 50 years, and if all goes as planned, will do so into the future.  Each project has a unique history and provides a puzzle piece in the full climate picture, but the trick is placing them together so that they form a richer image. Our flight route the past two days has overflown and linked us with each of these puzzle parts in order to capture overlapping data which will help us piece together the full image – an understanding of the past and the present to prepare for climate in the future.

So how do they all tie together?

EGIG (Expedition Glaciology International of Greenland) was a French traverse along a West Greenland ice flow line operated close to 50 years ago (1958/59 and 1967/68). Collecting snow and ice data the scientists were able to determine annual snow accumulation rates in a series of locations along the traverse.  By overflying these same locations EGIG’s snow accumulation rates can be used as a baseline for comparing our current data.

DYE2 dates back to the mid 50s, a relic of the cold war. Home to one of the Distance Early Warning (DEW) line radar stations it housed military teams monitoring the skies with radar for Russian bombers in the 1950s.  The site transitioned to a science station and in the 1970s a series of short 50-100 meter ice cores were drilled. Each core holds ice bubbles, small time capsules frozen in place, holding a record of the Earth’s past atmosphere, or as we know it, climate.  Data from the DYE2 cores allows us to map past climate to Arctic glacier extent.

GRIP (Greenland Ice Core Project) takes us back in time over 100,000 years.  The GRIP ice core was drilled in Central Greenland two decades ago. Located at 12,000 feet in elevation by the Summit Camp the core measures over 3000 meters long. Stretched down to Greenland’s bedrock, this core provides us with the longest record of Greenland’s climate history.

Operation Ice Bridge is a current mission collecting a wide range of information on the changes occurring in ice in the polar-regions.  The spring project is focused on measuring the rate of change in Arctic ice – both land and sea ice. This information will rely on measurements over a period of years, and draws on past studies and data collections.  Several of the Ice Bridge partners have been collecting Arctic ice data for a number of years.  Between the IceSat satellite that collected ice surface elevation from 2003-2009, and an annual ATM (Airborne Topographic Mapper) survey that operated over three decades, large reaches of the ice sheet have been measured establishing a history of precise ice surface elevations for a baseline comparison.

Mabel (Multiple Altimeter Beam Experiment Lidar) is the future.  Flying at 62,000 ft. elevation on an ER-2 aircraft Mabel is designed to take us back into space. Mabel is the mock design of the next ice measuring satellite, IceSat-2, scheduled to launch in 2016. Ice Bridge has linked with Mabel to fly transits in Greenland for some cross calibration of the measurements collected.

It is apparent that the past, the present and the future are all coming together by design, determined to piece together the climate picture of tomorrow.

Time takes on a new meaning in the field. Every moment is compressed in order to gain maximum yield. Applying human accounting, field time is limited by available resources, personnel, and funds, while using nature’s accounting the limits shift to windows of weather, and seasonality for ice phenomena. In the field both human and nature can conspire for or against you. A seasoned field crew learns to take advantage of every break from the planned work schedule to rethink, refine and reprogram their instruments and data collection.

After four days of intense commitment on the part of the flight crew, and the NASA and Wallops teams, the plane has traversed over 4450 miles round trip, spent two days under repair and will arrive back within hours. While the instrument teams await the return of the P-3 they work through data, check on equipment and ensure that all systems remain ready to begin as soon as IceBridge flights resume.

Lamont’s teams are responsible for the gravity and magnetics equipment. Gravity and magnetics are windows to the geology beneath the ice. The gravity measures density telling us of changes in structure or material beneath the ice sheet which result in a change in gravitational attraction or pull. Gravity is useful for locating changes but magnetics helps us ‘see’ more of what is under the ice, distinguishing between the low magnetic strength of soft mounds of sediment, to high magnetic strength of volcanic basalts. Understanding the Earth below is important in predicting future glacial movement and speed.

The magnetics base station has been visited to be sure it is intact, solar panels cleared of snow, and is recording data on the background magnetics from the Earth’s magnetic field. Collecting this data is essential since the plane magnetometer measures not only the geology beneath the plane as it flies, but the total magnetic field which includes changes in the Earthʼs field through the day. Collecting the background field allows us to back this out of the final readings to better understand the true signature of the geology beneath.

The gravity team also has a base station. They use this station, as well as a series of values that have been taken around Kangerlussuaq, as tie points for their data. Today is an opportunity to tie the readings to an absolute gravity reading by the Danish Geodynamics Department National Survey & Cadastre. A portable instrument will be used to collect readings at both the absolute survey point and the base station location. Gravity instruments are temperature sensitive so each is heated to an optimal temperature and must be kept at this range. The portable instrument has an internal heater and after several attempts it is clear the heater is not functioning correctly and will not allow the team to collect the tie in. The attempt will have to be revisited at some point in the future. For the immediate future, however, we hope to be back in the air flying tomorrow!

April 6th 2012 – it is tempting to look back and compare any undertaking in this region of the globe to this same date in 1909 when Robert E. Peary and Matthew A. Henson became the first men to reach the North Pole. How can we compare the intrepid spirit that drove the exploration by Peary and Henson to the carefully planned science missions in the polar regions today?

Perhaps the most natural connection is through the hand of fate and the crush of nature. Carefully planned and painstakingly executed missions can be quickly altered or shut down by either of these variables. Peary and Henson focused on being the first to attain geographic locations and develop an understanding of the northern regions of the planet. They made several attempts to attain the pole and were shut out by fate and nature in each earlier attempt. IceBridge has laid the same careful plans with backup missions and alternative flight scenarios but this all comes to a crashing halt when the hand of fate intervenes and knocks out an engine — #3 is down.

A downed engine flying in icy conditions is not to be taken lightly. It requires a return to the “mothership,” or Wallops flight facility in Virginia, to swap out the engine. Sounds simple, but as fate would have it we are simultaneously faced with the “crush of nature.” Storms moving through in series. Small breaks of weather here in Greenland would be enough to gamble on with a fully operational plane, but losing an engine reduces the payload by 40,000 lbs. 40,000 lbs. is a fair amount of fuel and will require a stop in Goose Bay Labrador for refueling. This means the weather must also be clear and ice free for a landing and take off when the plane arrives there. The flight time will be extended as the plane will travel at a reduced speed and lower elevation to reduce fuel consumption and overall strain on the plane.

Over the last two days all of the required conditions occurred in one 45-minute window, and the crew was prepared to slide through that narrow gap. We await news to hear of their arrival in Wallops, the assessment of the repair, and the possible date of return. Some days we think that things have changed a lot in the last 100 years, other days we realize that some things will never change.

The Greenland spring 2012 Ice Bridge mission is mid-season, which means a shift in focus from monitoring sea ice in the Arctic Circle to assessing land ice along the Greenland perimeter and interior. The mission is to measure the impact of a changing climate in one of the most remote places on Earth – ironically, a place that seems poised to lose that remoteness.

Tri-State: On my way to Copenhagen, the first leg of my journey, the climate irony of taking off over the tri-state area is not lost on me. Below a sinewy dragon of light sparkles brilliant amber in the evening dusk, evidence of the density of population in this region, and a flickering reminder of the human appetite for energy. Light and energy, the pulsing arteries that drive our businesses and our homes. Looking down one can almost track the watts as they move. I wonder how watts translate to degrees in Farenheit or Celcius. Traveling from such developed density it is hard to imagine there is a connection between here and Greenland, and yet the connection is measurable in the steady changes occurring in the icy reaches of our poles.

Copenhagen: Hours later circling over Copenhagen I look down at a waterfront dotted with windmills. Clean, white, spinning briskly bringing wind energy… I wonder if windmills are more accepted here than back on the U.S. coastlines. Perhaps acceptance comes with being faced first hand with the impacts. Will they slow the impacts already being felt in these northern climes?

Greenland: The last leg to Greenland is aboard Air Greenland, a plane painted an eye-catching red and white. The same red and white that graces the Erfalasorput, the name of the Greenlandic flag designed to symbolize the sun, the fjords, the sea and the ice. The transit places a magazine in my hands that boasts “Greenland a key player in global growth”. Fully 48 pages of stories and vignettes on companies and people who are making connections, developing skills, offering opportunity and making a difference for Greenland. Everything from oil exploration to mining strategic ‘rare Earths’, that small group of elements of critical importance to world industrial production, to building corporate social responsibility, to handling logistics and promoting responsible tourism can be found in this color spread. With the warming of the climate the resources of Greenland appear to have expanded in value. This is a Greenland poised to lose its remoteness.

One remarkable piece in this Greenland story catches my eye. “Future Geenland” a curated exhibition of how the explosion of opportunity facing Greenland may affect its future society and culture. What is so remarkable is the careful planning being considered in order to transition this once isolated country with its unique character and culture into the future…and the head curator is the Greenlandic geologist Minik Rosing. An odd choice one might imagine, yet Rosing spent his early youth on a caribou farm in a small southwestern fjord and has never separated from those roots. His research interests focus on how the geologic development of the Earth has been affected by the emergence of life. With a focus on the connection between resources and cultural development perhaps this is just a more modern, and more local rendition. All evidence points to Greenland’s vulnerable position between its cultural history and its future.  Who better to assist than one who connects his spirit to both this ancient culture and these ancient rocks with the resources they hold.

Blog by Hakim Abdi, LDEO

Satellite measures showing thinning ice on the Northwest Greenland glaciers prompted Operation IceBridge to include annual flights over this region. The area runs along the Baffin Bay coast, which is often covered in fog and low lying clouds forcing delays and reschedules. With the end of our season in sight we were forced to complete the flight in less than optimal conditions.

As we flew further south, approaching Upernavik, we encountered a dense cloud layer running inland along the glacier for several miles, and stopping at about the 2000 foot elevation. The scenery above the clouds showed high snowy peaks prompting a quick look at a digital elevation model of Greenland. The elevation around Upernavik and surrounding areas can reach up to 6000 feet, evident in the peaks we observed during the flight. This upper elevation was cloud free and we were able to collect data for monitoring any changes in ice thickness in these higher elevations.

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The arctic is home to several species of wildlife, some of whom are circumpolar. As we prepare to wrap up this season in Greenland Ithought I would share a few images of its charismatic residents. As summer approaches (it is presently at 23 degrees F), it has become possible to observe some of these species around the base. These include the Arctic Fox Vulpus lagopus, Arctic Hare Lepus arcticus, Snow Bunting Plectrophenax nivalis, Glaucous Gull Larus hyperboreus, (Greenlandic) Gyrfalcon Falco rusticolus, and the Common Raven Corvus corax.

From: Joël Dubé, Engineer/Geophysicist at Sander Geophysics, OIB P-3 Gravity Team

One of the instruments used in Operation IceBridge (OIB) is an airborne gravimeter operated through a collaboration between Lamont Doherty Earth Observatory of Columbia University and Sander Geophysics of Ottawa, Canada.  People from other instrument teams have been heard to call it a gravity meter, gravity, gravitometer, gravy meter, gravel meter, gravitron, or blue couch-like instrument. As operators of the gravimeter, we are referred to as graviteers, gravi-geeks or gravi-gods!  This tells a lot about how mysterious and unknown this technology appears.

Let’s start with why is gravity data being acquired as part of OIB, and how is airborne gravity data acquired?

The Earth’s gravity field varies over space according to differences in topography and the distribution of density under the Earth’s surface.  Essentially, the greatest density contrasts are between air (0.001 g/cc), water and ice (1.00 and 0.92 g/cc, respectively) and rocks (2.67 g/cc in average).  Therefore, gravity data can be used for modeling the interface between these three elements.  On OIB we have other instruments that can help with some of these measures. The laser scanning ATM system can locate the interface between air and whatever surface is underneath it with great accuracy, yet not below that surface.  The ice penetrating radar system (on OIB we use a system called MCoRDS) is successful at locating the interface of the ice and what lies underneath, however, if the ice lies over water there is no airborne radar system that can “see” through water.  Hence, gravity data is needed to help determine the surface bathymetry beneath floating ice, whether it is off shore in the ocean, or ‘on shore’ when the radar finds sub-glacial lakes under the ice sheet.  The gravity measurements enable the creation of water circulation models, helps predict areas at the bottom of the ice that might be early to melt, and  predicts ice transport.

An additional benefit of our collection of airborne gravity data is that it can contribute to increasing the accuracy and resolution of the Earth Gravitational Model (EGM). The EGM is determined only with low resolution measures in remote locations such as the poles, being built mainly from data acquired with satellites.  Our high resolution data can fill in details in the data.

Most people don’t know that it is possible to acquire accurate gravity data from a moving platform such as an aircraft.  Due to the vibrations and accelerations experienced by the aircraft, it is definitively a challenge!  There are four key elements that make this possible.

1- Very accurate acceleration sensors, called accelerometers are needed to measure acceleration forces.

2- The accelerometers must be kept as stable as possible, and oriented in a fixed direction.  This is a job for gyroscopes (a device for measuring and maintaining orientation) coupled with a system of motors that keeps the accelerometers fixed in an inertial reference frame, independently of the attitude of the aircraft.  This is why the system we use is called AIRGrav, which stands for Airborne Inertially Referenced Gravimeter.  Damping is also necessary to reduce transmission of aircraft vibrations to the sensors.  The internal temperature of the gravimeter also has to be kept very stable.

This is all good, however, the accelerations we are measuring this way are not only due to the earth’s gravity pull (a static force), but also (and mostly) due to the aircraft motion (a dynamic force).

3- To correct for item #2  a very accurate GPS data is needed so that you can model the aircraft motion with great precision.

However, despite all these best efforts, ‘noise’ in the readings remains, mostly from GPS inaccuracies and aircraft vibrations that can’t be detected by GPS, so:

4- A low pass filter must be applied to the data, since the noise amplitude is greatest at high frequency.

Even with all these elements accounted for, a number of corrections have to be applied to the data before they can serve the scientific community.  The corrections aim to remove vertical accelerations that have nothing to do with the density distribution at the earth’s sub-surface.

The ‘Latitude correction’ removes the gravity component that is only dependent on latitude.  That is the gravity value that would be observed if the earth was treated as a perfect, homogeneous, rotating ellipsoid.  This value is also called the normal gravity.  Since the earth is flatter at the poles, being at high latitude means you are closer to the earth’s mass center, hence the stronger gravity.  Also, because of the earth’s rotation and the shorter distance to the spinning axis, a point close to the pole moves slower and this will add to gravity as well (as there is less centrifugal force acting against earth’s pull).

Anything traveling in the same direction as the earth’s rotation (eastward), will experience a stronger centrifugal force thus a weaker gravity, and the reverse is true for the opposite direction.  Traveling over a curved surface also reduces gravity no matter which direction is flown, similar to feeling lighter on a roller coaster as you come over the top of a hill.  This is known as the ‘Eötvös effect’ and is taken care of by the Eötvös correction.  This correction is particularly important for measurements taken from an aircraft moving at 250-300 knots.

The ‘Free Air correction’ simply accounts for the elevation at which a measurement is taken.  The further you are from the earth’s center, the weaker the gravity.

To give you an idea of how small the gravity signal that we are interested in is with respect to other vertical accelerations that have to be removed, let’s look at the following profiles made from a real data set.  All numbers are in mGals (1 m/s² = 100,000 mGals), except for the terrain and flying height, which are in meters.

“Raw Gravity” in this diagram means that GPS accelerations (aircraft motions) have been removed from inertial accelerations.  Notice the relative scales of the profiles, starting at 200,000 mGals, down to 20,000 mGals when aircraft motions are accounted for, down to 200 mGals after removing most of the high frequency noise, and ending at 50 mGals for Free Air corrected gravity.  Free Air gravity is influenced by the air/water/ice/rock interfaces described earlier, and since OIB uses the gravity data to locate the rock interface (the unknown), Free Air gravity is the final product.  [As a side note, for other types of gravity surveys, we usually want to correct for the terrain effect (the air/water/rock interfaces are known in these cases), so that we are left with the gravity influenced only by the variations of density within the rocks (geologic information).  This is called Bouguer gravity and is also shown in the figure.]

Notice the inverse correspondence between flying height (last profile, in blue) and the profiles before the free air correction (going higher, further from the earth, decreases gravity), and the correspondence between terrain (last profile, in black) and the free air corrected data.

Now, let’s look at some data acquired during the current 2011 mission in western Greenland.

These three images are all of the same area called the Umanaq region along the coast of west Greenland. You can match the images by the black flight lines that run across them.  The first two images are from ETOPO1, a global relief model made from numerous data sets covering the entire Earth. The datasets above integrate land topography with ocean bathymetry as they are collected along the coastline. The data images can be “bedrock” (base of the ice sheet where the ice has been removed) or “ice surface” where you see the ice elevation overlaying the bedrock. The left panel is ‘ice surface’ over land but the ocean section shows as bathymetry, as if the water has been drained from the ocean showing the surface elevation of the bedrock under the ocean. In this section the lower elevation ranges from a low of blue to green to yellow, and where the ice surface is present, this higher elevation shows as red.

The middle panel shows both ice and water being removed, so you see only ‘bedrock’ elevation under the base of the ice sheet.

The right panel shows the actual Free Air gravity acquired in the last few weeks, which is like removing the ice and looking to see what is beneath.  Most channels, called fjords, are well mapped by the gravity data (showing as a low area in blue).  It is interesting to see that the gravity data infers the presence of a sub-glacial channel (shown in green and noted by the red arrow) where no channel is mapped (yet?) on the bedrock map.  The most likely reason for this is that this particular region has not been covered by previous ice radar surveys (there are huge portions of the Greenland ice sheet that remain unexplored).  Note that the MCoRDS ice radar data that was acquired as part of the current campaign will improve the resolution in this area, and when matched with this gravity data will enable a better comparison of both data sets in the future.

Congratulations you have just completed Gravity 101!

By Hakim Abdi, LDEO.
My first flight on the P3 and the scenery was nothing short of breathtaking. The science mission involved flights in the north over the Steensby glacier that passes through Sherard Osbron Fjord, and Ryder glacier constrained by the Victoria Fjord. In northeast Greenland we overflew the Hagen glacier and the Flade Isblink Ice Cap in Kronprins Christian Land.

The sheer dimensions of the fjord cliffs on the northern flights were striking. In north Greenland they were quite steep, at almost 90 degrees, and appeared to be carved with surgical precision. Formed in the last glacial period as Greenland was covered with ice and snow, the weight of the ice depressed the crust and glaciers cut through surrounding rock. Since the end of the last ice age, a phenomenon called ‘crustal rebound’ has taken place. The formerly depressed land masses have slowly risen in a process is called isostasy, resulting in these awe-inspiring cliffs.

Outside the scientific community, glaciers are sometimes thought of as ‘just a block of ice’, but they are much like landmasses in their own right, close to inland islands. They are solid, yet they are dynamic, with internal layers that record events during the lengthy history of their formation. They also have surficial features, including crevasses, such as those shown below. Crevasses are deep cracks in the ice sheet, equivalent to fractures in rock, and are formed due to a combination of factors including differences in the ice speed between the edges and center of the glacier, stresses generated by flow over an uneven terrain, and the stress created from the glacier’s lower layers being more malleable than its upper layers.

In Northeast Greenland we focused on the Hagen glacier and the Flade Isblink icecap. Like the flights over the northern glaciers we are resurveying historical ATM lines. Flade Isblink is a small, ~600 m thick, icecap in the furthermost northeast corner of Greenland located just south of Station Nord (a permanently occupied Danish scientific and military base) in Kronprins Christian Land. Flade Isblink faces the Polar Ocean and is separated from the central ice sheet so the age of the ice in this small icecap was recently determined to be much younger than the main icesheet. An ice core drilled by the Centre for Ice and Climate, Copenhagen University, suggests the age of this small ice cap to be between 2800 -4000 yrs (A. Lemark, 2010).

Working in the poles we are constantly reminded of our dependence on meteorology, and this project has dealt us a variety of different weather considerations. The most obvious is the weather we experience at the base. Storm season in Thule lasts from the 15th of September to the 14th of May; in other words encompassing fall, winter and most of spring! “Bad” weather is classified by temperature, wind speed and visibility, with the “storm condition” determining whether we can go outside alone, if we need to take a “buddy” or if we are allowed outside at all. Obviously this also affects whether the plane can take off for a day’s work.

We’ve had some weather passing through since last Monday, and have twice been in storm condition ‘Charlie’, where we are restricted to our dorms, or the hangar if we are on watch. We have meal ready-to-eat (MREs) on the ready for these occasions since the cafeteria will be inaccessible. This condition can last from hours to days. We have been fortunate with only quick ‘blow throughs’ and able to fit in a couple of short flights when conditions improved. I have plotted the air pressure for the last few days and it shows the two episodes of low pressure, which resulted in the bad weather passing over, and the flight we managed to squeeze in between the storms.

The second type of weather we have had to manage is conditions over the survey targets. John Sonntag from NASA/ATM gives us a briefing each night, showing weather models of the country. We are particularly interested in where there is cloud cover – since we want a clear view of the ice for the laser altimetry and for the DMS photo system. We also care about wind – turbulence can make it difficult for the pilots to fly the grid while keeping the equipment on target, and of course difficult for the passengers! Flight plans are given priorities – low, medium and high, and by balancing the weather forecast with the mission priorities John and Michael Studinger (the project scientist) have to figure out what our best target will be each day.

Finally, there is magnetic weather. Magnetic weather does not affect the atmospheric weather so most of us are not even aware of it, however it does affect the magnetic survey, and if lively enough it can even affect communications. Magnetic weather is variability in the earth’s magnetic field, and it is driven by activity on the sun, or solar flares. The Earth’s magnetic field varies from the equator to the poles with measures of approximately 30,000 nT near the equator to 60,000 nT (nanotesla) at the poles. Most of this field is from the Earth’s outer core but a small 1 to 2 % is the external field of solar interactions. It is this small external field that causes magnetic storms that last anywhere from six hours to several days. Impacts of magnetic storms are often only 50-300 nT, which might seem minor, but the effect on our instruments is important since it must be adjusted for.

There was a magnetic storm this weekend, but as the airport was closed for the weekend the plane wasn’t flying so we didn’t need to adjust for it. Had we still been in Kangerlussuaq it would have given us a good show of the northern lights. In Thule we are much further north and here the sun hasn’t set since the 16th of April! so no night-sky phenomena for us. The positive is the midnight sun works well for the night watch.

The North East Ice Stream is a fast-flowing glacier transporting ice from deep in the interior of the Greenland Ice Sheet out to the coast (see image showing a deep penetration into central Greenland). When it reaches the coastline it feeds 79 N Glacier. This area is heavily crevassed, evidence of the rapid ice flow. The cold blue ice and bare earth of 79 N seems particularly forbidding – even snow won’t settle here.

It is a two hour transit from Thule, in the north west corner of Greenland, to the survey area. The area is flat, white and empty. The only excitement is when we pass over the likely site of the old “Camp Century,” now buried under the ice, and moving with its flow. I note a “likely” site because the coordinates we have for it are old, and it will have moved. It is possible that one of the radar systems will be able to see where it sits now under the snow.

Located about 800 miles from the North Pole, Camp Century was a nuclear powered research facility built under the ice ~ 50 years ago by the US Army Corps of Engineers. For several years the camp operated as a mini city beneath the ice ignoring the forbidding environment, sub zero temperatures, winds that exceeded 125 mph, and an annual snowfall of almost 4 feet a year. However, the constant movement of the glacier forced the inhabitants to complete regular and extensive maintenance, which closed the camp after only 7 years. You can read more about this Arctic camp at: http://gombessa.tripod.com/scienceleadstheway/id9.html

We are beginning our focus on the land based ice of northern Greenland. Flying out of Thule places us close to Petermann Glacier situated in Greenland’s northwest corner. The focus of our first flight of this phase of the project (the overall 29th flight of the season!) is Petermann Glacier. Perhaps Greenland’s most newsworthy glacier of the past year, Petermann captured the attention of the world in August 2010 when it calved an approximately 97 square miles (251 square kilometers) block of ice, extraordinary in size, in fact the largest Arctic glacier to calve since 1962, almost 50 years! Four times the size of Manhattan, this three-dimensional block of ice cost Petermann about one-quarter of its 43 mile (70 kilometer) long floating ice shelf.

Petermann has the largest floating ice shelf in the Northern Hemisphere so calving icebergs are not unusual, but ones of this size will have an impact. Floating ice shelves, or ice tongues as they are often called, are the ocean terminating ends of ice streams that move ice off the continent. The shelf serves as a control on the flow of the ice stream once it hits the water, through the buoyant force pushing back against the ice shelf front. The sudden reduction in shelf size changes the balance and can cause the glacier to accelerate.

The most dramatic pictures of the loss of ice show glaciers retreating up valleys, thinning as they go; because the whole glacial system is connected, thinning at the far end has a large impact on this process. Breaking off the tip changes the driving forces that control the flow of ice further upstream, and with continuing mass loss, the thinning and speeding up of ice are reaching further and further inland. This can affect a very large area, so it doesn’t take much thinning to add up to a significant volume of ice loss. For our flight that means extending our survey grid further inland, so we can record the present ice surface to be able to monitor any changes in the future. Today’s grid will be followed by another flight (weather cooperating!), and then matched with last year’s grid. The goal of the three missions is to complete a 10-km-grid over the entire catchment area of Petermann Glacier. Glaciers, like watersheds, are referred to with catchment areas, but glacier catchments with their powerful forces do not always follow watershed boundaries.

There was a comment on the headsets early on in the flight, “Enjoy the scenery, because this is all we’ll get all day long,” and looking out the window, I understand. The survey grid is over flat white emptiness, so there isn’t much to look at on the surface. Of course it’s a bit more variable underneath the ice, so I could stand and watch the radar screen showing the shape of the bed, and from the same vantage point I could keep an eye on the changing magnetic anomalies.

Flying a grid survey lets us make a map of the base of the ice, telling us about its shape, and what it’s made up of. When we come back in the future to measure the change in the ice surface, our knowledge of the bed will help us to understand those changes. So while the scenery didn’t change much, there were still things happening at a pace that was once considered slow enough to coin its own meaning…at a glacial pace… That meaning is slowly shifting!

We flew our last science flight out of Kangerlussuaq Base (western Greenland) over the Geikie Peninsula, on the east coast of Greenland. This high priority mission had not been completed prior to this because of difficult weather in the peninsula area. The mission focus was to determine how the surface ice elevation and ice thickness have changed, as well as the capture the any existence and rate of glacier retreat. Gathering measurements focused on understanding how and why ice on Greenland and Antarctica is changing over time is the primary mission of IceBridge.  In order to collect these measurements we often in refly lines that were flown in previous years in order to measure change.  Today we reflew a main grid of lines over the ice cap on the Geikie Peninsula and then additional lines along a number of glaciers. The flood basalts of the Geikie Plateau are breathtaking.

Returning from the Geikie Peninsula, we flew along a track that was been remapped regularly for 30 years and gives a long history of how the ice in the center of the ice cap is changing.  The flights along the glaciers were especially scenic and the few windows on the P3 were full of people taking photos.

Runs along glaciers are always popular for that reason, particularly on the east coast where the fjords cut through high coastal mountains that extend well above the level at which the plane is flying.  However, the glacial valleys and fjords can also be quite windy.  On one flight, we encountered 70 knot winds and intense turbulence that sent everything that wasn’t held down, from laptops to coffee pots flying across the plane.  We spent most of that line buckled on our seats rather than taking pictures out the window.

Once more it is time to change locations, we are packing up to fly back to Thule, where we will finish out the campaign.  Packing involves more than just packing personal gear.  One of the gravity/magnetics team’s major projects will be taking apart the GPS and magnetics base stations, packing them in shipping cases and putting them on pallets. The Air National Guard will then load them onto their C130 cargo planes and transport them up to Thule.  The GPS ground stations are key to our measurements.  Having a receiver at a stationary location provides a baseline for the noise or jitter in the measurements, which we then remove from measurements taken on the plane.  This is especially important for the gravity team, because we need to use the GPS measurements to determine and remove airplane accelerations from our gravity measurements. The same idea applies to the magnetics measurements, as the Earth’s magnetic field is constantly varying and we want to remove that natural variation to isolate any anomaly resulting from the rocks we are flying over.  Once in Thule we will quickly get the stations reinstalled so that they have 24 hours to settle prior to our first flight.

Our mission was to collect some long survey lines down the center of some of Greenland’s most spectacular southeastern glaciers. The study design would require us to complete a transect across the Greenland ice sheet, fortunately at a location when the country undergoes a noticeable taper. Starting at Kangerlussuaq, our base on Greenland’s west coast, we flew across to the Kangerdlugssuaq Glacier on Greenland’s east coast (we too have trouble with all the Kanger’s in Greenland)! Kangerdlugssuaq Glacier is a major contributor of ice into the ocean. Together with Jakobshavn it drains an estimated ten percent of the Greenland Ice Sheet into the ocean.  We will focus on several other southeastern outlet glaciers as well, collecting flight lines on Helheim and Midgard, both extremely important, Fenris and Steenstrup, and others in the vicinity.

Extending the survey lines mid-center in the glaciers will allow us to collect gravity and magnetics data to assist in detecting the presence of bedrock sills under the ice. Sills are common in fjords, forming a shallow lip near the glacier outlet to the ocean, where it creates a basin. The presence of a sill limits the flow of ice out of the fjord. Locating any sills that exist in these draining glaciers is important for the modeling that is such a key part of our scientific understanding of the polar regions and their response to climate.

Our flight today is slow and low flying, so that we can collect good gravity numbers, and somewhat surreal.  As we cruise we move in radio silence to avoid interference with our instruments; at a 600 foot elevation, we are a full hundred feet lower than some of the icebergs in the fjords around us!  We are somewhat like a large bird taking stock of our surroundings as we soar through the terrain.

The Operation IceBridge (OIB) mission is a truly collaborative project with several agencies and multiple instruments involved in collecting independent measurements. The data is then analyzed concurrently to develop an understanding of the ice processes underway. The measurement of sea ice is an excellent example of how multiple methods of measurement are needed to collect the necessary data.

Sea ice: Uniquely challenging, yet extremely important, sea ice measurements show us both the aerial extent and the thickness of the year’s ice. Aerial extent is important for the albedo, or energy reflection, that the ice returns without absorption. Thickness is used to distinguish multi-year ice from the annual ice, and while both are needed for providing data for models of how it is changing, sea ice thickness is somewhat tricky to measure. Because of the complexities OIB uses two independent sets of instruments to collect sea ice data and then compares the results. The Airborne Topographic Mapper (ATM) instrument collects ice surface elevation, which is then compared with the sea-surface elevation where open water leads exist exposing the water surface (photo). This provides what is called the ‘freeboard’ or the amount of ice that sits above the sea surface. If you know the density of the seawater and the density of the ice you can calculate the ice thickness from the freeboard. This is the same method we use to measure the size of an iceberg, since ice is only 9/10’s the density of water causing approximately 90% of the ice to sit underwater.

There are, however, several tricky parts to this method of measure. First, the further from the open water leads we are, the less accurate the freeboard measure is. Second, it can be difficult to know the density of the ice column. Snow that falls on the ice adds to the elevation, but snow is much less dense than ice. We need to know the differences since we are interested in the extent of the ice under the snow. This is where OIB radars contribute.

There are four different types of radar currently involved in this operation; each has a strength and function. The challenge is to select radar that has the correct sensitivity to measure the small amount of thickness involved. OIB uses two different radar for sea ice measure, accumulation radar, that they use to measure the depth of sea-ice, and the snow radar that reflects off the snow/ice boundary to measure the snow depth above ice. Between the two radars and the ATM measures there is a system of checks and balances on the determination of the freeboard of the ice.

Magnetics: 7 of the first 9 flights of OIB flew northwards out of Thule. This allowed us to take a quick look at the magnetometer data from adjacent lines to see how it was working. Since the magnetometer measures the total magnetic field (including changes in the earth’s field through the day, changes in the field produced by the plane and all its instruments as it flies, and changes in the field caused by the geology that we fly over) we will need to fly a magnetic compensation flight, to determine how the magnetic field of the plane changes with changes in direction. Our schedule has been so packed that compensation flights are scheduled for days when the weather doesn’t allow us to venture over the ice. In the meantime, we can only process the data to remove the effects of the earth’s field changing through time. This is done by subtracting the field measured by the stationary base station from the field measured by the sensor on the plane.

Magnetics and gravity together are key to helping us understand the geology that lies underneath the ice. The gravity can tell us if there is an anomaly, or a change in formation or material under the ice sheet by it’s gravitational pull. Large geologic structures often have more pull, as do small but much denser structures. While gravity is useful for locating these anomalies, the magnetics can help us determine still further what is under the ice by distinguishing between weakly magnetized structures, like mounds of soft sediment, from highly magnetized structures like volcanic basalts which have retained the magnetic signature that was locked into them when they cooled and solidified and may be high in iron content. These distinctions are important since we are looking for geologic features that exist under the Greenland outlet glaciers that will affect the way that they flow into the sea. Mounds of soft sediment will not behave the same in front of a fast flowing glacier as a hardened substrate. In addition these geologic formations are essential for determining: how the sea water underneath interacts with floating glacial tongues; where the ice is currently grounded; or where it might reground were it to melt back. These are all key questions in the OIB mission.

The map shown plots the flight lines over a low resolution regional magnetic anomaly grid that already exists for the area. It is clear that the higher resolution data from the magnetometer on the aircraft fits well with the satellite generated regional grid, suggesting that the instrument is working correctly. Flying the gravimeter and the magnetometer together improves the interpretation of the data from both. A satisfying result this first northern phase of the project.

We have moved south! One of the many challenges of our Greenland survey is the need to switch bases in the midst of the season since Thule Air Force Base also serves as a staging location for a major resupply mission for many of the Arctic outposts.  The whole set up has to be packed up and redeployed to Kangerlussaq, a small town along southwestern Greenland of about 600 people located at the head of Sondre Stromfjord, a feature extending 90-100 miles out to the coast. The edge of the ice cap is about 10-15 miles to the east and glacially fed rivers run from the ice down to the fjord. Located on the site of a former cold-war era US Air Force base it serves as Greenland’s international airport.

The move involved packing up not only the personnel, but pallets of sensitive instruments and equipment, the base stations that were in place for calibration of the data etc.…a major effort!  However we have had a very successful first leg to the IceBridge mission while in Thule, with 8 successful sea ice flights (and 2 glacial flights), which was the main goal of the first part of the deployment. Moving south will also bring us closer to several of key glaciers we plan to monitor, including the Jakobshavn Glacier.

We should note that while we managed the relocation to Kangerlussuaq, we have had considerable delays in taking to the air again due to a series of propeller repairs needed on the P3.  The very cold temperatures, -28°C (-18°F) when we walked the 600 m over to the airport this morning, have been the cause of some of this.  Kangerlussuaq has no heated hanger so the plane sits outside in the cold, causing gaskets to contract and hydraulic fluid to leak out. However we are back flying and collecting impressive data!

Our first return to the air was a survey of Jakobshavn Glacier, located about 250 km north of Kangerlussuaq on the west coast of Greenland.  Starting at the fjord where the glacier meets the sea, we worked inland for about 150 km with closely spaced lines near the coast and more widely spaced lines inland running an exact repeat of surveys done during the 2009 and 2010 IceBridge campaigns.  These repeat surveys are extremely important for some of the fast changing glaciers. For the Jakobshavn area once inland from the fjord and the coastal hills, the ice cap is flat with no obvious large-scale topography to show the location of the glacier that forms a fast flowing ice river though the ice cap.  However, once we cross over the glacier, the flat and somewhat featureless surface of the ice cap changes rapidly to a broken-up and crevassed surface as the rapidly moving ice deforms as it flows.

Jakobshavn is a large and important glacier, draining over 6% of the Greenland ice cap and more potential sea level rise than any single source in the Northern Hemisphere. It is also one of the most rapidly changing glaciers in the world with thinning rates estimated at up to 15 meters per year. Jakobshavn over the last decade has followed a pattern of calving and retreating, and as recently as July 2010 suffered a significant retreat of ~1.5 km. This very active glacier is the subject of intense amounts of study, so flying the same survey lines several times allows us to determine the pattern of thinning over the entire glacier.  This is essential for understanding the processes at work.  A surprise result from first two years of IceBridge flights is that the thinning extends much further inland than had been suspected; in fact it extends beyond the limits of our survey.  As a result, a second mission to Jakobshavn is planned for this year to extend the survey inland an additional 75 km.  When those lines are reflown next year, we will have a more complete picture of the evolution of the glacier. It is findings such as this that have made IceBridge so key to helping us understand the changes in the polar regions.

By Brian Moses

This past week, Operation IceBridge undertook a detailed survey of the ICEX camp, situated on the ice sheet north of Alaska. This complex 3 day mission involves a transit to Fairbanks, AK over the top of the world, refueling in Fairbanks and flying the survey on day two, and a low-altitude nighttime flight back to Thule.
The transit flight took off at 10 AM on Tuesday, 30 hours delayed due to a storm that had all of Thule in lockdown. The flight included a short survey period and carried the NASA P3 within 180 miles of the North Pole, with some impressive visuals. After more than 8 hours in the air, we land at 1pm Fairbanks time…time is a fickle thing, when you’re flying over the top of the world! Arriving in Fairbanks from Thule Air Force Base, it was hard not to chuckle at the commonplace “Welcome to the Arctic!” sentiments seen around Fairbanks, as we found it hard to get over how warm it is outside!

ICEX (short for Ice Exercise) 2011 – is an operation of the U.S. Navy, part of a series of submarine operations they run in the challenging Arctic environment. As part of ICEX 2011 a camp the size of a small village has been constructed just north of Prudhoe Alaska, and is being operated for ICEX by the Applied Physics Laboratory of the University of Washington, and members of the U.S., Canadian, and British navies. Since the camp is built on Arctic ice it is drifting and collecting tracking data on ice flow as well as other parameters.

The IceBridge ICEX2011 camp survey lines were extremely complex from an organizational point as well as an operational point. Organizationally it involved numerous meetings with the several agencies involved to facilitate timing and location of data collection and ultimately integrating this data with the suite of measurement being collected by these other agencies, both from the ground and from a twin otter aircraft. These pieces all merged will be a benchmark data set for sea ice research. Operationally it involved a series of flight passes completed at several elevations. A flight ‘course’ of sorts was marked out in a grid on the ground for IceBridge to follow in their data collection. Flying the survey was a challenge because of the camp’s location on the floating ice sheet. The ice under the station was drifting to the north prior to the P3 take off, but once in the air it shifted to an eastern drift and began to be accelerate, causing mid air recalculations and adjustments based on visual observations.

(For a bit of history, drifting Arctic stations have long been a part of Arctic research, and have a similarly long connection to Lamont. 1937 saw the first Soviet floating station established to collect data on the Arctic basin, but the presence of these stations in the Arctic really accelerated during the International Geophysical Year (1957-58). It was during this time that the US ran several floating Arctic stations, the first of which was ‘Station Alpha’, where Lamont research scientist Ken Hunkins was stationed to collect data. Hunkins expanded our understanding of the Arctic throughout his career.)

The return trip to Thule took off at 1am, flying through the Aurora Borealis and at low altitude across the sea ice. It was incredible to see the aurora out the windows of the plane, and the terrain mapping laser on the ice below, while the pilots followed the survey line at 2500 feet. The coloring of the airplane wing is because all vessels (water and air) have a red navigation light on the port side and a green light on the starboard side. This blinking light combined with the long exposure photo provide the red glow.

It was an uneventful day, flying into the sun for eight hours and landing at Thule to a treat – the first day above zero degrees Fahrenheit!

Note: Brian Moses is part of the Lamont Polar Research team and is part of the IceBridge deployment to Greenland 2011.

Operation IceBridge has returned to the Arctic for a second Greenland season collecting critical measurements of Arctic sea ice cover and thickness and Greenland’s coastal outlet glaciers. Traveling on a DC8 outfitted as a cargo plane with only 6 rows of seats, the team flew from Baltimore MD to Thule in northern Greenland.
The workhorse for the field season will be the P3, which has been in Wallops VA being outfitted with the lasers, snow accumulation radar, ice thickness radar, gravity and the new instrument this season a magnetometer – which we are fondly calling the stinger! This piece of equipment will be extremely useful in helping to interpret some of the geologic information provided by the gravity data.

Sea ice will be the focus of the early mission flights since the ice has a seasonal fluctuation, thus capturing data while the ice is at its greatest extent is key. Sea ice, frozen ocean water that forms as the atmospheric and water temperatures cool, starts as a patchy crust on the surface but expands from September through March to a solid icy covering. Separated into first year and multiyear ice this covering can actually measure from 2 meters to 3 meters thick respectively.

This white covering on the ocean surface is a key feature in keeping the Earth’s climate cool as it reflects the sun’s energy rather than absorbing it as the dark ocean water would. For January 2011 the agency that tracks sea ice cover, U.S. National Snow and Ice Data Center (NSIDC), reported the lowest measure of sea ice extent since satellite measurements of its cover began in 1979. They hypothesize that one reason for this might be increasing amounts of open ocean. IceBridge measurements can help with predicting the future of this trend.

The arrival into Thule was lovely – flying in over the sea, with the sun low, and catching the edges of icebergs so they glowed orange while the sea ice around them stayed white. The sea was still frozen in the bay, creating interesting patterns with plenty of icebergs and pressure ridges. A denser patch of icebergs announced a glacier nearby, and land soon came into view. We came in over snow-covered hills, and some of the landscape was marked by very distinctive flat tops. One of these was Dundas Fjeld (Uummannaq in Greenlandic) in the photo above.

On the base our living quarters are very comfortable, but it still pays to get a lift in a vehicle if we want to travel across the base – it’s pretty cold out there, especially when the wind blows. Around the base, it isn’t uncommon to see arctic foxes and hares. The foxes I have seen have been dark, and moved quickly, the hares on the other hand are white and fuzzy and pretty well camouflaged and seemingly unfazed by our presence, even following us around if we look interesting – watching us with big, black eyes. They have very long legs made for running, but I haven’t seen it happen.

Weather permitting we look forward to a full field season of measuring and assessing this northern reach of the cryosphere.

We are finally back from Greenland, bringing to a close the data collection piece of the spring 2010 Ice Bridge campaign. During my month-long piece in this campaign our time was split between two West Greenland base -camps, Kangerlussuaq and Thule (also known as Qaanaaq). Thule, at the northern end of Greenland, is the farthest north I have ever been. It is a place where one can step out the door and actually see sea ice – truly amazing! During the early spring part of the campaign the scientists on board the DC 8 were actually able to walk on the sea ice, however the seasons are changing and by mid May when we arrived there in the P3 the sea ice was breaking up, and most of the snow had melted. These images of the Dundas Mountain in Thule, captured earlier in the campaign by Jim Cochran’s photograph (top), and again by me in May (bottom), tell the story. The snow had melted exposing the rock, dust and gravel of the strange looking mountain.

From the windows of the lounge of the inn where we stayed, I could see stranded icebergs lodged in the sea ice. From this perch one can sometimes see polar bears - if lucky! While on board the P3 flying over sea ice, I kept a close watch on the sea ice to spot a polar bear. While I did not get to see any, I did manage to spot the breathing holes in sea ice made by the seals. Both the seals and the polar bears rely heavily on the sea ice for specific habitat needs that are key in their life cycle. Sea ice is crucial to their reproduction, hunting and transit so changes in overall cover and thickness are a real concern. Just as glaciers and icesheets are changing in recent years, sea ice is also influenced by climate changes. Over the past 30 years, scientists have observed an approximate 8% loss in arctic sea ice area, and a significant loss of multiyear ice resulting in an overall thinning of the sea ice cover. With this decline in the natural habitat of Arctic seals and polar bears these species are threatened, and the polar bears in particular may face extinction. During the entire IceBridge campaign, there have been a series of flights to monitor the changes in sea ice as we hope to better understand the changes occurring at the poles.

http://arcticclimatemodeling.org/Movies/sea_ice_dvd_sample.html

Although we battled weather with snow, rain with wind speeds in excess of 35 knots, and had to navigate around the volcanic ash, we did manage to complete all of our high priority flights. This aggressive flight schedule was far from effortless, and at the end of the trip there was big sigh of relief among the crew and science team members (below).

In retrospect, the whole experience was extremely rewarding. This was my first trip to Greenland and I have enjoyed every moment of it. The team members were extremely knowledgeable in their field and very cooperative and helpful. The down days were fun when we took time off to explore the land on foot. The locals we came across were friendly, helpful, and as technology savvy as the rest of the world with impeccable manners and were extremely helpful. Football (soccer), it seemed, was a craze among the Greenlanders as were colorful houses, trendy phones and fashionable dresses. Their cheery disposition is evident in the youth who were thrilled to meet us all and pose for photos!

I thank all the scientists and crew members on this mission, the local support groups at Kangerlussuaq and Thule and everybody back home at Lamont who have helped to make this trip a memorable experience for me.