A Second IceBridge Experience: It Just Gets Better

By Nathan Kurtz, NASA’s Goddard Space Flight Center and University of Maryland, Baltimore County

Looking back, I’m extremely happy that my second time on the IceBridge mission to the Antarctic was a much more intense experience than my first. Last year bad weather kept us grounded quite often and I was limited to going on three flights over the vast extent of sea ice that surrounds the continent. But this year we hit the ground running, well, flying I should say. There were many more flights, more thrills, more snow, more ice…or was there more snow and ice? In fact, one of the main goals of the IceBridge project is to find out whether the Antarctic is gaining or losing ice. While some regions are gaining ice and others are losing it, the question remains as to whether the sum of the parts is in balance. More importantly, how will the southern polar ice cover drive and respond to changes in the climate? How will these climate impacts affect humanity?

An apron of sea ice floats in front the Brunt Ice Shelf, seen on the first flight of the Antarctica 2011 campaign. Credit: Michael Studinger/NASA

With these questions in mind the DC-8 airplane used for IceBridge launched tirelessly day after day to provide some answers. The plane was loaded with instruments to get a unique look from the air that we cannot get with our eyes and hands. It’s amazing for me to think about what great things just a bit of electricity powering the scientific instruments can accomplish (not to mention the massive amounts of coffee apparently fueling the instrument operators). Some electricity fed through an antenna mounted on the aircraft wings produces a radar pulse that can tell us how thick the snow is beneath us. Electricity through a different antenna produces a radar pulse that can tell us how thick the ice is. While even more electricity fed other instruments such as the lasers, gravimeter, and the often-times spectacular photography of all the beautiful areas we pass over.

Outcroppings near Marie Byrd Land. Credit: Michael Studinger/NASA

With all that sensitive equipment loaded on the plane our next step was to fly over interesting areas to measure. We started out with flights in the Weddell Sea to measure the thickness of the sea ice surrounding the Antarctic continent. Antarctic sea ice is a fantastic sight to behold as the strong ocean dynamics in the region create a wide variety in the types of structures that we see. Like a snowflake, no two views of the sea ice are ever the same. In some areas the ice is very consolidated with the ice floes constantly crashing into each other and creating human-sized ridges. In other areas the ice has moved apart, exposing the ocean to the cold polar air and creating intricate geometrical structures as the water freezes and gets stirred together by the wind and ocean.

It is freezing and dynamic processes such as these which determines how much sea ice there is surrounding the Antarctic continent. As a scientist, one of my goals is to use the data collected during these flights to determine how the sea ice is changing and if so, what is causing the changes? How will these changes in such a remote area impact the world at large? It is thought that changes in the sea ice cover will have a large impact on the global temperature by changing the amount of solar radiation absorbed by the Earth. But presently it is not well known how changes in the global temperature will affect the Antarctic sea ice cover. While one may expect warmer temperatures to reduce the amount of ice, it is also possible that complex feedback mechanisms between the ocean and atmosphere could cause the Antarctic sea ice cover to increase with a warming climate. Connecting the observations taken during these IceBridge flights to those from satellites over the past decade will be critical to determining what factors have and will play a part in impacting the ice. While it will take some time to understand what the IceBridge measurements are showing us, there are high hopes for learning a great deal from what has been done.

Path of the IceBridge sea ice flight over the Weddell Sea. Credit: Michael Studinger/NASA

While on my previous flights over sea ice with IceBridge we would often fly near the great ice shelves surrounding the Antarctic continent. To me, the great white ice sheets always looked foreboding, as if they were waiting to swallow up the airplane if we dared venture too far into the interior of the continent to spy on its secrets. This year during my first land ice mission to Pine Island Glacier I half-expected something terrible to happen as soon we crossed the threshold from the ocean to the continent. Thankfully, the plane held a steady pace as if it had absolutely no concern for where it was going. In fact, the plane ended up dutifully flying all over the continent carrying me to some of the most remote and hostile environments on the planet. On the way I saw desolate islands buried in ice, giant crevasses, flew perilously close to lonely mountains with peaks just barely reaching up from the 1+ mile thick sheet of ice covering the land, and so much more. But it didn’t seem scary at all, in fact it was quite beautiful! Well, from 1500 ft above the ground everything looked beautiful. At times, the sensors in the plane showed surface temperatures below -50 F and winds blowing at more than 60 mph. Blowing snow was easy to spot with such strong wind. Perhaps not such a cheery and inviting environment to visit, but perched safely on the plane it was easy to appreciate the splendor of the world below. Interestingly, the map display on the plane showed nothing but an ominous black void beyond 80 degrees latitude, the edge of the world apparently. But the mapmakers have it wrong. While the bottom of the world is certainly a vast abyss, it is of white snow and ice rather than a black nothingness.

Given the enormity of the sheet of ice covering Antarctica it’s hard to imagine that changes could also be happening to it. Yet, as I’ve learned many times throughout my experience with IceBridge, it takes sophisticated instruments to learn what is really happening there. With many more flights to go, and countless more hours spent by scientists looking at the instrument data, we will hopefully find out soon enough.

Flying Under A Satellite

By Michael Studinger, IceBridge Project Scientist, NASA Goddard Space Flight Center

Punta Arenas, Chile – Better understanding of changes that occur in the polar ice sheets and sea ice requires observations over many years. With Operation IceBridge we make sure that there are no gaps in these critical measurements. In particular, we “bridge” the gap in laser altimeter measurements from space between ICESat, which ended in 2009, and the follow-up mission ICESat-2, which will launch in 2016. Using data from these two satellite missions and combining them with our aircraft measurements we will be able to build a time series of measurements that spans 17 years. In order to build long time series we often have to combine measurements from different instruments and satellites and it is important to make sure we calibrate and validate these measurements against each other, which will allow us to detect changes in the polar ice sheets and sea ice. The goal of Thursday’s IceBridge mission into the Weddell Sea was to better understand how radar altimeter measurements from ESA’s CryoSat-2 satellite can be combined with laser altimeter measurements from NASA’s IceBridge satellites. 

Scarred and chiseled sea ice in the Weddell Sea, where the DC-8 followed in CryoSat-2’s tracks on Thursday’s IceBridge flight. The DC-8’s shadow appears as a dark speck in the lower right. Credit: Michael Studinger/NASA

With IceBridge we are in a unique position to answer these questions because we fly both kinds of instruments on the DC-8 aircraft. In order to compare our measurements we have to fly the DC-8 directly beneath the CryoSat-2 satellite and collect data at the same time in the exact same location. It sounds easier than it is. Many things have to come together to make this happen. First, the weather in the Weddell Sea needs to be suitable for our flight. We need a large, cloud-free area beneath us, which is very rare to find. Second, we need the CryoSat-2 spacecraft on an orbit that allows us to take off from Punta Arenas and fly the DC-8 on the satellite ground track at the same time the spacecraft passes overhead. Third, we need this location to be over a certain type of sea ice that is suitable for comparison of the different measurements. Last, but not least, the weather conditions in Punta Arenas have to be suitable for safe takeoff and landing. Today, we were facing very strong winds that have been close to preventing a flight. While we were flying over the Weddell Sea our colleagues informed us that the winds in Punta Arenas had become so strong that the G-V aircraft had to be moved to Puerto Montt because the wind conditions exceeded the safety specifications for safe parking on the ramp for the G-V. All in all, flying an aircraft directly beneath a satellite in one the most remote parts on Earth is far from trivial. Today, everything went well and the DC-8 flew along the CryoSat-2 ground track in the southern Weddell Sea while the spacecraft passed overhead. The ice conditions were just perfect.

After our rendezvous with CryoSat-2 we reversed course on the ground track to fly back on the same line for 130 kilometers. We did repeat measurements over the exact same segment of our survey line over the course of one hour in order to track the drift of the sea ice. Wind and ocean currents move sea ice floes around. We can estimate how fast and in which direction the sea ice is moving by correlating patterns in our data between the three passes. It is very difficult to make these measurements from space.

After reaching the northern end of our survey line we transit back to Punta Arenas, knowing that we accomplished another landmark sea ice mission for Operation IceBridge.

DC-8 joins G-V for Antarctic IceBridge flights

The Dryden-based DC-8 flight crew handles the plane on its first Antarctica 2011 flight. Credit: Michael Studinger/NASA

By Michael Studinger, IceBridge Project Scientist, NASA Goddard Space Flight Center

Punta Arenas, Chile – Today marks a milestone for IceBridge. For the first time, both NSF’s Gulfstream V (G-V) and NASA’s DC-8 aircraft took off from Punta Arenas for science flights over Antarctica. 

The G-V, with NASA’s Land Vegetation and Ice Sensor (LVIS) on board, headed toward Evans Ice Stream, which flows into the southern part of the Ronne Ice Shelf in Antarctica. 

The DC-8, with its suite of IceBridge instruments, headed toward the Weddell Sea to measure the thickness of the sea ice and the snow on top of it along two 1,700-km-long transects that cross the entire Weddell Sea from east to west. It’s like flying from Chicago to Miami and back at 1,500 feet above the ground. This mission is an exact repeat of two missions that we have flown in 2009 and 2010. The goal is to measure how much sea ice is being exported through the “gate” connecting the tip of the Antarctic Peninsula with Cape Norvegia and determine the changes that occur over time. The export of sea ice from this area is a major contributor to the total ice volume exported into the Antarctic Circumpolar Current.

The DC-8 takes in a stunning view of the Brunt Ice Shelf on its first Antarctica 2011 flight. Credit: Michael Studinger/NASA

The Weddell Sea encompasses a large area and the chances of getting such a large area cloud-free are small. We rely on several different weather forecast models, satellite imagery and meteorologists at the Punta Arenas airport to get a picture of the weather conditions in the survey area before the flight. It requires many years of experience to interpret the different pieces of information and make a decision in the morning whether we launch a mission into the Weddell Sea or not. There is not a single weather station in the Weddell Sea or nearby to provide observations we could use to confirm the model predictions. Imagine needing to rely on a weather forecast back at home that has no weather data between Chicago and Miami. During the flight we encountered the expected mix of clouds, fog and sunshine. We often were able to fly below the clouds and continue to collect data. All in all a great start to our Antarctic campaign.

Measuring Gravity From a Moving Aircraft

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. Some people from other instrument teams 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 me summarize the basics of airborne gravity data acquisition for you.

But first, why is gravity data being acquired as part of OIB?

The earth’s gravity field is varying in space according to variations in topography and density distribution under the earth’s surface. Essentially, the greatest density contrast is 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 modelling the interface between these three elements. The ATM system (laser scanner) can locate the interface between air and whatever is underneath it with great accuracy. The MCoRDS system (ice penetrating radar) is successful at locating the interface underneath the ice. However, no radar system can “see” through water from the air. Hence, gravity data can help determine bathymetry beneath floating ice, either off shore or on shore (sub-glacial lakes). This in turn enables the creation of water circulation models and helps to predict melting of the ice from underneath. Also, airborne gravity data can contribute to increasing the accuracy and resolution of the Earth Gravitational Model (EGM), which is determined only with low resolution in remote locations such as the poles, being built mainly from data acquired with satellites.

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- You must have very accurate acceleration sensors, called accelerometers.

2- You must keep these accelerometers as stable as possible, and oriented in a fixed direction. This is a job for gyroscopes 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, but also (and mostly) due to the aircraft motion. And to correct for that:

3- You need very accurate GPS data, so that you can model the aircraft motion with great precision.

Despite these best efforts, noise remains, mostly from GPS inaccuracies and aircraft vibrations that can’t be detected by GPS, so:

4- You have to apply a low pass filter to the data, since the noise amplitude is greatest at high frequency.

The AIRGrav system on-board the P-3 aircraft. Gravimeter (right), rack equipped with computers controlling the gravimeter and GPS receivers (center) and operator (left). Credit: Joël Dubé

Furthermore, a number of corrections have to be applied to the data before they can serve the scientific community. The corrections aim at removing 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 (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 other way around in the other 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.

A visual summary of gravity corrections. Credit: Stefan Elieff

“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 find 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. 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.

Ice elevation (left), rock elevation (middle) and Free Air gravity data (right). Greenland 2011 flight lines shown in black. Gravity data is preliminary and is not yet available for scientific analysis.

The left panel shows the elevation of the rocks, or of the ice where ice is present. It is as if the water has been drained from the ocean. The middle panel shows only the bedrock elevation, both ice and water being removed. The data is from ETOPO1, a global relief model covering the entire earth. The right panel shows the Free Air gravity acquired in the last few weeks. Most channels, called fjords, are well mapped by the gravity data. It is interesting to see that the gravity data infers the presence of a sub-glacial channel (shown 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 acquired as part of the current campaign will improve the resolution in this area and will enable for a better comparison of both data sets in the future.

Advancing Ice Science from All Angles

From: Kathryn Hansen, NASA’s Earth Science News Team

On May 5, 2011, IceBridge surveyed the Devon Ice Cap (above) and two glaciers on Bylot Island (below). Credit: NASA/John Sonntag

Thule, Greenland — On May 5, 2011, Operation IceBridge completed its third and final flight in conjunction with an experiment operated by the European Space Agency (ESA).

The experiment, called CryoVEx, is a series of ground-based calibration sites for ESA’s ice-observing satellite, CryoSat-2. IceBridge flights over these calibration sites ultimately are expected to provide data to evaluate and improve remote-sensing measurements.

“The collaboration will also help us to jointly interpret measurements collected from the ground, air and space, advancing our understanding of ice sheets and sea ice, and their response to climate change,” said Michael Studinger, IceBridge project scientist.

The morning of May 5 started like most days in the field with IceBridge – with an early-morning weather brief. Poor weather afflicted most remaining science sites accessible by the P-3 that day, so IceBridge teams looked toward Canada. A phone call to researchers at Summit Camp on Canada’s Devon Ice Cap – the site of the final CryoVEx site – revealed good conditions.

In the Arctic, however, weather can turn on even the best-informed observations and predictions.

Summit Camp on Canada’s Devon Ice Cap is visible from the P-3, which overflew the ground-based calibration site on May 5, 2011. Credit: NASA/Digital Imaging Sensor

“We flew over the camp and the corner reflectors several times,” Studinger wrote in the mission’s situation report. “Conditions changed quickly. On the last flight we could barely see the camp.”

Still, the clouds parted long enough for the Airborne Topographic Mapper (ATM), a laser altimeter that measures surface elevation, to achieve good data from 75 percent of the area surveyed on the Devon Ice Cap.

Weather was more favorable south of Devon Island over Bylot Island, where the P-3 flew a first-time survey of two Bylot glaciers and collected good data over 90 percent of area surveyed. Credit: NASA/Michael Studinger

The campaign’s previous collaboration with CryoVEx included a flight on April 15 over sea ice, and on April 26 over the interior of the Greenland Ice Sheet.

“This has been a great collaboration between ESA and NASA for cryospheric and airborne science, and will no doubt lead to further joint activities in the future,” Studinger said.

The Long Wait

From: Lora Koenig, NASA’s Goddard Space Flight Center, Operation IceBridge Deputy Project Scientist

It arrived, finally it arrived! Yes, the new B200 windshield is here and currently being installed. You begin to realize how remote Kangerlussuaq, Greenland, is when you need something. In the United States you can overnight ship almost anything from Chicago style pizza to Memphis ribs to aircraft windows, but not here. Here, in Kangerlussuaq, the only way to get things this time of year is on one plane that arrives from Copenhagen, Denmark, Monday through Friday at 9:30 a.m. local time.

When the B200 windshield cracked on Monday the plane crew immediately ordered a new windshield to be sent from NASA Langley. It was shipped on Tuesday and arrived today. During the time that it took the windshield transit, the B200 plane crew took out the old windshield and prepped the plane for the new one.

I have learned a lot about aircraft windshields the past few days. For instance aircraft windshields are installed using a sealant (a glue to secure the windshield inside a bolted frame). Even though it has warmed up significantly since we first arrived, it’s just 27 F (-3 C) outside. That’s quite balmy compared to the -8 F (-22 C) temperatures of last week, but the windshield sealant needs temperatures around 77 F to cure. The aircraft is in a hanger but it is still too cold to cure quickly. The B200 crew spoke with some of the Air Greenland crew who lent us some Infrared (IR) heating lamps. The IR heating lamps will allow us to install the window and cut the curing time in half so we can get back in the air sooner.

Right now the window is being installed and sealant applied. Overnight, the window will sit under the IR lamps. On Saturday the plane will undergo a test flight with only the pilots onboard to ensure the aircraft is safe. If all goes well by Monday we will be back up and flying the B200, which carries a high-altitude laser altimeter called the Land Vegetation and Ice Sensor (LVIS).

In the meantime the LVIS instrument has been resting but Elvis sightings around Greenland have remained high.

The first Elvis sighting was Rob White (left) from the B200 crew, and the second Elvis sighting was Shane Wake (right), an LVIS instrument operator. 

Mission Mop Up

From: Kathryn Hansen, NASA’s Earth Science News Team / Cryosphere Outreach

April 8, 2011

Kangerlussuaq, Greenland — Today’s mission was a mix of the exciting and dull – from spectacular scenery over an ice cap, and up some glaciers and over Jakobshavn’s calving front, to the monotonous but scientifically important back-and-forth mapping of Russell glacier. It was essentially a “mop up” mission, combining targets from three separate flight plans.

We starting the day off flying over Sukkertoppen Isflade, our first ice cap of 2011! Flying over the blanket of ice, the scene abruptly ends as ice cascades down steep terrain into an open-water fjord that separates the ice cap from the Greenland Ice Sheet. Ice caps, while separate from the main ice sheet, are also undergoing changes and contribute to sea level rise.

An open-water fjord separates the Sukkertoppen ice cap from the Greenland Ice Sheet. Credit: NASA/Michael Studinger

Continuing south, we flew along several glaciers starting with Taserssuak (not thinning) and later on over Kangiatanunatasermia (thinning). The difference is interesting, as both glaciers are fed by the same fjord system. Scientists want to keep watch over these regions to continue to see how the change is changing.

We flew four glaciers fed by the Nuuk flord system including this glacier with a colorful name, Akugdlerssupsermia. Credit: NASA/Robbie Russell

After hitting some clouds as expected from the morning’s weather brief, we headed back north and reflew the center flow line of Jakobshavn — always spectacular — before flying over Illulisat Isfjord, which was surprisingly free of ice. The reason for the ice-free conditions was unknown to scientists onboard. There could have been fewer calving events, warmer water, or wind patterns that pushed ice out of the area.

“Half of the Illulisat Isfjord was open water with several fishing boats in the area, something I have never seen before,” said Michael Studinger, the mission’s project scientist.

A camera mounted on the belly of the aircraft captured this image of a fishing boat (top) in the Illulisat flord, which was mostly open water with a few visible patches of ice. Credit: NASA/DMS team

Next it was on to Russell Glacier, just outside of our home base, Kangerlussuaq. Back and forth, this was a true “moving the lawn” pattern. I may have even taken a brief nap. But to scientists, this mapping is critical. A radar instrument onboard will get a good look at what’s below all that ice and help scientists better understand how the bedrock influences the flow of glaciers.

Battling the Arctic Chill

From: Kathryn Hansen, NASA’s Earth Science News Team/Cryosphere Outreach

April 6, 2011

Kangerlussuaq, Greenland — It may seem obvious, but the Arctic is cold. I was surprised to arrive in Kangerlussuaq, Greenland, to see the hills and streets covered with snow and temperatures that make you second-guess the wisdom of leaving any skin exposed.

In 2010, the Kangerlussuaq leg of Operation IceBridge began about a month later, in May. What a difference a month makes. The hills were snow-free, flowers beginning to bloom, days were long, and the river rushed to break up the last chunks of winter ice. On down days, crew and science teams hiked, biked and went fossil hunting. Now we mostly stick to the warm indoors. Most of us, however, are willing to brave the cold and dwindling hours of darkness to catch a spectacular show of the northern lights.

This time lapse of the northern lights consists of 30-second exposures spanning just over an hour. We took turns behind the camera, running inside every 15 minutes to quickly warm up. Credit: NASA/Jefferson Beck

It turns out that the aircraft also battles the cold. On April 5, we planned to fly the mission’s first science flight from Kangerlussuaq to collect data over Jakobshavn — Greenland’s fastest moving glacier. At 6 a.m. it was just -11 F. The coffee pot onboard froze and fractured.

Shortly after take off, the cold temperatures resulted in a mechanical issue on the aircraft that forced an early return to Kangerlussuaq, Greenland. The P-3’s adept aircrew was quick to diagnose and resolve the issue.

John Doyle, a P-3 flight mechanic, is on the aircraft early and prepared for the cold. Credit: NASA/Kathryn Hansen

On April 6, crew started the day extra early at 5:30 a.m. when the temperature measured in even chillier at -18 F. Additional heating for an extended period prior to flight led to a successful first flight from Kangerlussuaq. And what a spectacular, clear flight.

The DMS, a downward looking camera system, captured this shot of Jakobshavn’s calving front. Credit: NASA/DMS team

Instrument teams onboard the P-3 also battle with the effects of temperature. Scientists with the laser altimeter use hair dryers to warm up the instrument, but too hot is also problematic. Scientists working with the radar instruments prefer the cooler time of year before melt ponds appear on the ice, complicating the way light reflects from the surface.

Having overcome challenges posed by the cold, we’re looking forward to a long series of land ice flights over Greenland. There’s word among the crew that the new coffee pot should arrive in a few weeks, in time for IceBridge’s return to Thule. Thanks to the P-3 crew for what might be the best cup of Joe in Greenland!

In the absence of coffee pot, P-3 crew construct a makeshift filter out of a water bottle. Credit: NASA/Kathryn Hansen

A Five-Hour Survey

From: Kathryn Hansen, NASA Earth Science News Team / Cryosphere Outreach

April 3, 2011

Colors show elevation differences across the airport’s ramp in Kangerlussuaq, Greenland. The map is used to calibrate airborne instruments. Credit: NASA/ATM team

Kangerlussuaq, Greenland — During the last IceBridge campaign, based in Punta Areans, Chile, we described a three-hour ramp survey. Scientists drove a truck with a GPS antenna affixed to the roof to map the precise elevation of the airport’s entire ramp — the pavement next to the runway where the aircraft spends each night. The ramp map helps researchers calibrate science instruments on the aircraft.

Here in Greenland, at Kangerlussuaq International Airport, the same activity on Saturday, March 3, would turn into a five-hour survey.

“This has to be the biggest ramp in the world,” said Kyle Krabill who drove the car, bringing me along as the unsuspecting passenger.

The task started that morning after idling for an hour on the ramp to calibrate the GPS. Then, we rolled off at a whopping 15 miles per hour, windows rolled down and 80’s Danish music blaring. Back … and forth … and back … and forth … we traced around the perimeter of the ramp and then inward, as if we were mowing a lawn of pavement.

A time lapse shows one hour of four-hour-long ramp survey. Video credit: NASA/Jefferson Beck

“See how easy it is to be a scientist?” Krabill joked. But it turns out that driving the car is just the beginning.

Krabill is part of the team that runs the Airborne Topographic Mapper (ATM), an instrument flying with IceBridge. ATM pulses laser light in circular scans on the ground. The pulses reflect back to the aircraft and are converted into elevation maps of the ice surface.

Toward the end of each flight, ATM laser elevation data are also collected during a pass over the ramp. Putting the data all together (including the dizzying ground-based ramp survey), and knowing the precise location of the aircraft (via a technique called “differential GPS”) scientists can decipher and eliminate some of the inherent error that comes with flying a laser scanner, such as errors in range — the physical distance to the ground — and in the team’s knowledge of the way in which the scanner is mounted in the aircraft.

“Differential GPS is fundamental to what we do,” said John Sonntag, ATM senior scientist. “It’s tremendously powerful, taking position error down from about 10 meters to 10 centimeters or better — a huge improvement.”

P-3 Back in Service

April 2, 2011

Kangerlussuaq, Greenland — The P-3 is ready to return to IceBridge just 30 hours after the aircraft’s prop valve failed on Friday, April 1. Here we list highlights from the tremendous effort by aircraft crew who were responsible for the speedy return to flight.

P-3 crewmen John Doyle and Brian Yates work on engine #2. Credit: NASA/Jim Yungel

Friday morning:

1. From Kangerlussuaq, Greenland, get permission to ferry the aircraft to its home in Wallops Island, Va.

2. Line up customs at Dover Air Base

3. File a flight plan

4. Fuel the aircraft

Friday night:

5. Remove the propeller on engine #2

Saturday morning:

6. Replace the P-3 propeller valve

7. On the ramp, let the aircraft’s engine run

8. Functional checkout flight (successful!)


9. Take a much-deserved mandatory hard down day in Wallops Island, Va.


10. The P-3 is scheduled to depart Wallops at 7 a.m. EDT and arrive in Kangerlussuaq at 4:30 p.m. local time, ready for a possible flight on Tuesday!

Engine run up under way on the ramp at Wallops. Credit: NASA/Jim Yungel