Monthly Archives: March 2013

Crossing the Basin: IceBridge in Alaska

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By George Hale, IceBridge Science Outreach Coordinator, NASA Goddard Space Flight Center

Why does IceBridge fly all the way to Alaska when the rest of the campaign is in Greenland? It’s an understandable question considering how far away these two locations are. But when you consider the economic importance of the regions north of Alaska and how dynamic and varying sea ice in the Arctic is, the picture becomes clearer. Much like last year, the IceBridge team made the 8 hour transit flight from Thule to Fairbanks early in the campaign.

Flight path from Thule to Fairbanks.
Flight path taken from Thule, Greenland, to Fairbanks, Alaska on Mar. 21, 2013. This route and the more southerly return leg have been flown in every IceBridge Arctic campaign. The flightplan was renamed this year as a tribute to sea ice scientist Seymour Laxon. Credit: NASA

Ice on the Move

At first glance it might be easy to assume that Arctic sea ice is uniform, but the region’s geography, ocean and wind currents and the ever-changing nature of ice itself mean that conditions can vary significantly across the Arctic Basin. “There are lots of different thickness gradients across the basin,” said Jackie Richter-Menge, sea ice scientist with the U.S. Army Corps of Engineers and co-lead of the IceBridge science team.

Ocean currents like the Beaufort Gyre continuously spin in the Arctic Ocean, driving ice cover along the coast of North America toward Greenland where it is compressed into thicker multi-year ice. The presence of multi-year ice is one of the biggest differences between the ice cover off the coast of Greenland and in the region of the Arctic Basin north of Alaska, which is recently dominated by ice that forms in the winter and disappears in the summer.

DMS mosaic of ice in the Beaufort Sea.
Digital Mapping System (DMS) image mosaic of ice in the Beaufort Sea. The lighter colored portion at the bottom right is thick sea ice, the darker blue-gray areas are thinner ice and the dark segment in the middle is open water. Credit: NASA / DMS

This seasonal ice cover is becoming more prevalent in areas north of Alaska as the thicker multi-year ice gradually melts. On the Mar. 22 IceBridge flight Richter-Menge saw firsthand how things have changed since she flew over the region earlier in her career in the 1980s. “It was notable how deep we went in the basin without seeing multi-year ice,” Richter-Menge said. IceBridge didn’t see multi-year ice until they were about 1000 kilometers from shore. In the early 1980s it could be found between 150 and 200 kilometers out.

Getting Better Data

These sorts of changes, along with environmental and economic concerns, contributed to the science communities increased desire for data on sea ice this part of the Arctic Basin. IceBridge had conducted transits of the entire basin from Thule to Fairbanks in previous campaigns, but starting in 2012, the mission started doing a temporary deployment in Fairbanks to get more data on areas north of Alaska.

IceBridge’s increased coverage is adding to the body of knowledge on ice in this region adding a new level of detail. “It gives us a more complete view of what’s going on in the basin,” said Richter-Menge. The data collected on these flights give more geographic coverage to IceBridge’s sea ice data products, especially the quick look product that debuted during last year’s Arctic campaign. This dataset came about in response to a need for near real-time sea ice conditions for use in seasonal sea ice forecasts.

Graph of Arctic sea ice volume from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS)
Graph of Arctic sea ice volume from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS). Credit: Polar Science Center / University of Washington

Along with data on sea ice freeboard, the amount of ice floating above the ocean’s surface, many in the scientific community have taken an interest in IceBridge’s snow depth measurements. Snow depth gives a way to measure changes in precipitation rate and differences in accumulation affect how much snow is available for melt ponds. As conditions warm in the summer, snow melts and accumulates in ponds. These ponds are darker than the surrounding snow, trapping more of the sun’s heat and further accelerating melting.

Richter-Menge (left) and the IceBridge team before a flight over the Beaufort Sea on Mar. 22, 2013.
Jackie Richter-Menge (left) and the IceBridge team before a flight over the Beaufort Sea on Mar. 22, 2013. Credit: NASA / Jim Yungel

Learning and Teaching

As a guest on the flights out of Fairbanks Richter-Menge got a chance to see firsthand how IceBridge collects sea ice data. Being able to witness this complicated and involved process helps give a better-rounded picture of the mission, Richter-Menge said. In addition to the data-collection that takes up each flight, Richter-Menge got to see the work it takes to choose which mission to fly each morning. “It was impressive to watch the whole decision-making process for choosing flight lines,” said Richter-Menge.

And as is often the case, the flow of information goes both ways. Richter-Menge and fellow sea ice scientist Sinead Farrell spent plenty of time on their flights sitting at a window aboard the P-3 and explaining what everyone was seeing. “We are learning a lot about sea ice with them here,” said Christy Hansen, IceBridge’s project manager.

NASA Operation IceBridge: Notes from the Field (Arctic 2013)

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By Sinead Farrell, Sea Ice Scientist, NASA Goddard Space Flight Center / University of Maryland

Editor’s note: This entry was originally posted on the Scientist’s Soapbox, a blog published by the Earth Science System Interdisciplinary Center at the University of Maryland in College Park, Md. 

Introduction:

The NASA Operation IceBridge mission began the Arctic 2013 research campaign on Monday 20th March. The mission will survey the Greenland Ice Sheet and sea ice pack of the Arctic Ocean. The NASA IceBridge mission is now in its fifth year and continues to measure Arctic sea ice thickness and snow depth. These data continue the time series of ice thickness measurements begun with NASA’s ICESat in 2003, and will provide a link to the NASA ICESat-2 mission, due for launch in mid-2016.

Surveys are conducted using a specially-equipped P-3B research aircraft (see photo below) that flies above the ice carrying a number of science instruments including radar and laser altimeters, and high-resolution cameras. This year the first flight took place from Thule, Greenland over Arctic sea ice north of the Lincoln Sea, on Wednesday 20th March. IceBridge flew beneath the European Space Agency’s CryoSat-2 satellite, that carries a special radar altimeter known as SIRAL. The mission was designed to fly a gridded-survey beneath the satellite to help validate CryoSat’s measurements over sea ice. The aircraft then transited from Thule across the Arctic Ocean to Alaska on Thursday 21st March. Over the coming days IceBridge will attempt a number of sea ice flights over the Beaufort and Chukchi Seas from a base at Fairbanks International Airport, Alaska. ESSIC’s Sinead Farrell hopes to participate in the first Alaska mission on Friday 22nd March, pending good weather. Dr. Farrell is a sea ice scientist and member of the NASA IceBridge science team.

View of a sea ice lead from the NASA P-3B.
View of a sea ice lead from the NASA P-3B. Credit: NASA / Christy Hansen

Daily Blog Posts:

Tuesday 19th March: Arrived in Fairbanks, Alaska on Tuesday to slightly warmer spring temperatures than I had expected. After organizing a rental car, figuring out how to use the engine heating block and the all-wheel drive, I headed for the hotel to unpack and (re)familiarize myself with the locale. The last time I enjoyed an extended visit to Fairbanks was exactly ten years ago, while I was conducting my graduate studies at University College London. Back then I also participated in a NASA airborne campaign over the Chukchi, Beaufort and Bering Seas aimed at validating the NASA AMSR-E radiometer. Things have not changed much in Fairbanks over the years!

Wednesday 20th March: The first in a series of IceBridge science flights was successfully completed on Wednesday. Although the mission was conducted far away over Arctic sea ice northwest of Greenland it was nonetheless a very exciting mission to follow. I was involved in designing a set of gridded flight-lines over the ice such that our airborne survey would provide temporally and spatially coincident measurements with CryoSat-2, while it passed high over-head. This is a technically challenging flight to conduct but things worked out well. The sea ice appeared more dynamic than we had expected, but the number of cracks in the ice, known as “leads”, will actually help in the data analysis aimed at inferring sea ice thickness. While waiting for the IceBridge mission to transit from Greenland to Alaska, I will spend time visiting the International Arctic Research Center (IARC), at the University of Alaska – Fairbanks (UAF). On Wednesday I had the opportunity to meet with some of my colleagues at IARC to discuss on-going and future projects to better understand the diminishing Arctic sea ice pack. I was also able to attend a lecture by Dr. Ron Kwok of NASA’s Jet Propulsion Laboratory on the topic of “Recent Changes in the Arctic Sea Ice Cover: A remote sensing perspective”. Fortuitously there are many national and international sea ice scientists visiting UAF right now to participate in meetings and workshops. Some are even en route to conduct field-work on the sea ice near Barrow, Alaska. Although it’s very cold (-19 degrees Celsius this morning!) and snowing, this is a great time of the year to be in Fairbanks!

Thursday 21st March: Thursday began with the exciting news that the NASA P-3 was en route to Fairbanks. Today’s mission from Greenland to Alaska was flown along what is called the “Laxon Line”. The flight is named in honor of University College London Professor Seymour Laxon. Seymour, my graduate advisor, died tragically 3 months ago. Seymour was a pioneer in the use of satellite altimeters to study sea ice and was the lead sea ice scientist on the CryoSat-2 mission. Today we measured ice thickness and snow depth along a flight line that crosses most of the Arctic Ocean. Thanks to a good tail-wind the P-3 landed one hour early in Fairbanks, right around lunch time. I was really lucky to watch the plane land with my colleagues Jackie Richter-Menge from the Cold Regions Research and Engineering Laboratory (CRREL) and Pam Posey from the Naval Research Laboratory (NRL). Once through customs we met our colleagues off the plane and welcomed them to snowy Alaska!

Friday 22nd March: On Friday we hope to conduct a third sea ice mission over the Arctic, weather permitting. We always need good weather to fly our surveys since clouds can potentially interrupt the measurements we make from the aircraft. We’re particularly interested to see what is happening to the sea ice in the Southern Beaufort Sea this year after the ice pack suffered a wide-spread “break out” event in mid-February. This event caused the ice pack to fragment into smaller floes and become more dynamic. Although these break-out events are not unusual in this region, they do not normally happen in February, the dead of winter. We will provide more updates as the day progresses.

The NASA P-3B on the ramp at Fairbanks, Alaska.
The NASA P-3B on the ramp at Fairbanks, Alaska. Credit: NASA / Jim Yungel

IceBridge Arctic 2013 Check Flights Complete

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By George Hale, IceBridge Science Outreach Coordinator, NASA Goddard Space Flight Center

On Mar. 14 and 15, the IceBridge team carried out project check flights in preparation for the Arctic campaign. After an engineering check flight earlier in the week to make sure everything is properly secured inside the aircraft, scientists and a small number of instrument operators board the P-3 to begin flights over the Wallops Flight Facility airfield and beaches near Wallops Island, Va., to test the Airborne Topographic Mapper (ATM) and Digital Mapping System (DMS) and over the Atlantic Ocean to test the Multichannel Coherent Radar Depth Sounder (MCoRDS), the snow and accumulation radars, and Ku-band radar altimeter.

These check flights have two main purposes. The first is to test the equipment to make sure it’s all in working order and the second is to collect data that is used to calibrate the instruments. Every time an instrument is installed in a research aircraft it’s important to make sure that nothing has changed since the last time it was flown.

Flight paths for both IceBridge check flights.

Flight paths for IceBridge check flights on Mar. 14 (blue) and Mar. 15 (red). Credit: NASA

Ground tests can catch many alignment and installation problems, but the real moment of truth comes in flight tests. On the afternoon of Mar. 14, the IceBridge team took off for flights near Wallops to test the ATM and DMS systems and check other electronics. By flying a level flight at varying altitudes, the teams can collect data that ensures their instruments are properly calibrated.

Different materials reflect light to varying degrees, which can make a difference with a laser-based instrument like ATM. Because IceBridge is measuring snow and ice, highly reflective materials, the ATM team will often test over sandy areas the beaches near Wallops. This is because sand reflects light in a similar way to ice. Another test is to check areas near each other with widely different albedos, for example, the white numbers and surrounding dark pavement on the runway. If light and dark targets next to each other show the same elevation then the instrument is calibrated properly.

The NASA P-3B at Wallops Flight Facility before the IceBridge check flight on Mar. 14, 2013. Credit: NASA / Kyle Krabill
The NASA P-3B at Wallops Flight Facility before the IceBridge check flight on Mar. 14, 2013. Credit: NASA / Kyle Krabill

Similarly, the team tests the DMS instruments to make sure the camera is aligned properly and that focus and frame rate are set appropriately. The rate at which the DMS camera captures photos depends on the aircraft’s speed and altitude, with lower altitude and higher speeds needing a faster rate to ensure proper coverage.

On Mar. 15, the team took off in the morning to do final checks of the P-3B’s radar instruments. Instead of flying along the beaches near Wallops, the P-3 headed out 200 nautical miles over open water in the Atlantic Ocean. The reason for doing this test over the ocean is twofold. First, U.S. law prevents IceBridge from operating its radars inside the country, and second, the ocean surface acts almost like a mirror for the radar, making it ideal for testing. By comparing transmit and return signal strengths at different altitudes, the team can make sure the radar is working properly.

The P-3B returns to Wallops after the first of two IceBridge check flights. Credit: NASA / Kyle Krabill
The P-3B returns to Wallops after the first of two IceBridge check flights. Credit: NASA / Kyle Krabill

Signal strength, however, is only part of the picture. MCoRDS is made up of several antennas in an array, with each antenna’s signal recorded separately. To make sure that each element is aligned correctly, the P-3B climbs to a high altitude and banks left and right while researchers measure how the return signals change during the maneuver. These maneuvers are also the reason why the radars are tested on a separate day from ATM and DMS. Once the plane banks more than 15 degrees, its wing blocks these instruments from seeing GPS satellites in orbit and both ATM and DMS need accurate GPS data to work properly.

With the check flights complete it is nearly time for IceBridge scientists, instrument team members and flight crew to make the trip to Thule, Greenland, to start the 2013 Arctic campaign. The P-3B is scheduled to make the transit flight from Wallops early on the morning of Mar. 18, and the first science flight is scheduled for Mar. 20.

Preparations for Arctic Campaign Under Way

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By George Hale, IceBridge Science Outreach Coordinator, NASA Goddard Space Flight Center

An IceBridge field campaign is the culmination of months of planning and preparation. At January’s science team meeting, scientists focused the campaign’s goals and provided mission planners the details needed to finalize flight plans. With these final details ironed out the next step was to start preparing the tools of the trade, IceBridge’s aircraft and instruments. For the past several days, instrument teams and aircraft technicians at NASA’s Wallops Flight Facility in Wallops Island, Va., have been getting the P-3B ready for the 2013 Arctic campaign, which is scheduled to have its first science flight on Mar. 20.

Operation IceBridge is but one of several missions to use NASA’s P-3B airborne laboratory. After each mission, this aircraft returns to its home base at Wallops where it undergoes repairs and routine scheduled maintenance needed to keep it flying at peak efficiency and where science instruments are swapped out. This rotation of airborne science missions keeps the Wallops aircraft team busy, preparing between three and five missions per year. “Sometimes it’s more and sometimes it’s less,” said P-3B flight engineer Brian Yates. “We’re working on some relatively large projects, so we have five this year.”

NASA's P-3B airborne laboratory in a hangar at Wallops Flight Facility as it is being prepared for the upcoming Arctic campaign.

NASA’s P-3B airborne laboratory in a hangar at Wallops Flight Facility as it is being prepared for the upcoming Arctic campaign. Credit: NASA / George Hale

After the aircraft’s maintenance is complete and the previous mission’s equipment has been removed, the IceBridge team starts installing the mission’s suite of science instruments. This process can be generally divided into a few portions: installing the instrument and the equipment needed to control it and collect data, testing the individual instruments and checking to make sure the aircraft and instrument suite work together as they should.

The first step is installing the components that gather the data, such as cameras, radar arrays and laser transceivers. The Airborne Topographic Mapper (ATM) laser and Digital Mapping System (DMS) cameras are installed in bays on the underside of the aircraft. Each of these instruments looks down through windows in the plane’s belly. The Multichannel Coherent Radar Depth Sounder (MCoRDS) antenna is attached to the underside of the aircraft. Previously this has included antennas under the wings, but IceBridge is flying with a trimmed down MCoRDS instrument with an array beneath the P-3B’s fuselage.Additional radar instruments like the accumulation and snow radars and Ku-band radar altimeter are also installed at this time.

The MCoRDS radar antenna on a cart prior to being attached to the underside of the P-3B.

The MCoRDS radar antenna on a cart prior to being attached to the underside of the P-3B. Credit: NASA / George Hale

While this hardware was being installed on the plane, other members of the instrument team put together all of the hardware needed to operate the instruments in metal racks that are then securely bolted to the floor of the plane. Making sure everything is securely fastened is crucial because of the often turbulent nature of low-altitude polar survey flights.

ATM equipment racks waiting to be installed in the P-3B.
ATM equipment racks waiting to be installed in the P-3B. Credit: NASA / George Hale

Once everything is in place and secured the next step is to make sure the instruments work properly. This means rounds of testing both on the ground and in the air. Ground testing involves checking instrument connections and alignment. “We’ll check on the camera to make sure it’s seeing through the window ok and not catching the edge,” said DMS field engineer Dennis Gearhart.

Everything being used in this IceBridge campaign has flown before, but it’s important to make sure the instruments are working properly.”We want to make sure things work as well as they did when they were put into storage,” said ATM program manager James Yungel. To do this, the ATM team will bounce the laser off a ground target 500 feet away.

The MCoRDS antenna secured to the underside of the P-3B.

The MCoRDS antenna secured to the underside of the P-3B. Credit: NASA / George Hale

The real test of all this work comes with the mission’s check flights on Mar. 13 and 14. The first flight, known as an engineering check flight is carried out with flight crew only and is to ensure that everything is properly installed and secured. Scientists and instrument operators participate in the second flight, where instruments are powered on and tested. “The check flights are a final arbiter,” said Yungel.

This year’s IceBridge Arctic campaign will run from Mar. 18 through May 3. The P-3B will operate out of airfields in Thule and Kangerlussuaq, Greenland, and Fairbanks, Alaska.