Monthly Archives: May 2012

Devon Ice Cap: CryoVEx 2012 airborne campaign wrapped up

Should we stay or should we go … from Indriði Einarsson and Henriette Skourup, DTU Space

On 1 May, we arrived in Thule AB, which is the closest and most convenient airport for flights to Devon Island. Grisefjord in Canada is actually closer to Devon, but the runway is often hampered by strong cross winds which makes landings impossible.

Summit camp Devon Ice Cap

On Devon Ice Cap the ground team from the Geological Survey of Canada and the University of Alberta was already established in a camp near the summit (see photo) and the corner reflectors were in place. The plan was to survey along two CryoSat ground tracks of 3 May and 22 April and to re-fly flight lines (line 623 and 450) from campaigns in previous years (see map below).

Devon Ice Cap and planned flight tracks

On the morning of 2 May all the instruments were up and running and the weather was perfect with clear blue skies and a light breeze from the northeast. Everything was ready and perfect, and with hindsight maybe a bit too perfect. When starting the aircraft engine the electrical system failed and the silence spoke its own words. The airport’s hours of operation are strictly limited to 08:00–16:00 local time, which leaves only a small window for delays in the flight plan. As the time passed by the hope for a Devon flight for that day quickly faded. Nevertheless, thanks to the huge effort from the crew and local mechanics the aircraft was ready in the afternoon. According to the Met Office, the weather looked promising for a second attempt the next day.

Work in the Arctic demands patience - Sine and Indriði from DTU

Unfortunately, the satellite image for the area on the morning of 3 May showed low clouds covering the ice cap. We have the indispensable possibility of calling the scientists on the ice cap for the local weather. A call at 09:00 to Dave Burgess (from Geological Survey of Canada) working on the icecap could not, however, provide a definitive answer to the question: “Should we stay, or should we go?” He reported clear sky at the summit, but thick low clouds to the Northeast and East. We decided to wait another hour to see how the weather developed but in a second phone call we were told that the weather hadn’t changed.

With the weather prediction for the next day in mind, 50/50 chance for good conditions, a decision was made to give it a try. We took off in flurries from Thule AB. As the flight to Devon in a Twin Otter takes about 1.5 hours, there was plenty of time to ponder about the weather situation on the ice cap.

The hopes grew, as there were some clearings outside Thule AB, and fortunately, Mother Nature was in a good mood. The weather on the ice cap was perfect and all the planned tracks were flown, including the CryoSat track, and the corner reflectors at summit were right on spot.

Snow structures from wind erosion on Devon Ice Cap

With Devon Ice Cap done, the CryoVEx 2012 main validation sites were covered, and we only had to return to Kangerlussuaq where the IceSAR team was waiting for the Twin Otter to repeat tracks from mid-April (see blog posted on 26 April). We left Thule AB on 4 May between heavy flurries. On the way to Kangerlussuaq we used the opportunity to measure the sea ice in Baffin Bay and the Greenland ice sheet along a CryoSat ground track.

The CryoVEx 2012 airborne campaign has been a success and we have been quite lucky with the weather both at the validation sites and on most transit flights. We have gathered airborne data along 16 CryoSat ground tracks covering different sea ice conditions, parts of the Greenland ice sheet, as well as the local ice caps Devon and Austfonna. An overview plot of all pre-processed laser scanner data acquired during the campaign is shown in the map below.

Heights from pre-processed laser scanner data from CryoVEx 2012

On to Station Nord

From Indridi, Sine & Henriette (DTU Space), on the way to Thule Airbase, 29 April

Continuing our campaign to validate CryoSat, the last days of April were busy. We flew over the Austfonna ice cap on Svalbard to measure Kongsvegen Glacier and the sea ice in Fram Strait on the way to Station Nord, the most northeasterly habited point in Greenland, and we underflew CryoSat t over the sea ice north of Greenland.

Ice cap meets the sea

At the Austfonna ice cap the ground team from University of Oslo and Norwegian Polar Institute had put up five corner reflectors prior to the flight. These are used as a reference point to validate the penetration of the radar signal in the upper layers of the ice cap, and to check the timing of the ASIRAS radar.

We had fairly good weather conditions over the ice cap with just a few low clouds in the west and northwest. Although the laser scanner doesn’t penetrate through clouds, the cover was rather thin and data was gathered over most of the flight lines. The ASIRAS radar does see through clouds so radar surveying was done for all the lines.

We flew six lines of high priority and expect to have hit four out of the five corner reflectors several times. Two hits were confirmed in the air on the realtime radar display. This is possible as the radar response shows a very characteristic circular shape above the ice surface when flying over the reflector, see the capture below. Along a few lines we surveyed all the way to the open water where the ice cap gives way to the sea as the photo at the top shows.

Radar response to corner reflector

After this flight we packed our gear and headed towards Station Nord. On route from Longyearbyen to Greenland we were able to survey Kongsvegen glacier, and the sea ice in the Fram strait.

Konsvegen Glacier (H. Skourup)

As our survey altitude is about 300 m, from time to time we get a glimpse of the Arctic fauna from above. This time we were lucky to see group of whales in a pond of open water in the ice pack. Unfortunately we do not have any pictures, as even whales are only a few pixels wide in images taken from this altitude.   

Sea ice

We landed at Station  Nord at 14:08 UTC. Fortunately, the personal at the station were willing to support another flight, as this was the only chance to have an underflight of CryoSat over the sea ice north of Greenland. We only had time for a quick lunch, as we had to take off again at 15:40 because we wanted to rendezvous with CryoSat at 16:40 on a flight line about an hour from the station. We succeeded in surveying the line between 16:00 and 18:00 UTC where we ‘met’ CryoSat at 82N 52.6 15W 29.2 at 16:40:20, see photo of navigation screen.

Navigation screen

Another successful day. The next main task will be the flight over Devon Island, we’re crossing our fingers for nice weather!

A successful day over sea ice

From Henriette and Sine (DTU) and Tommaso (ESA), Svalbard, 30 April

Spectacular scenery heading north

After a day of being grounded owing to bad weather, the morning briefing of the 27th restored our confidence that our mission to collect sea-ice thickness measurements, north of the Svalbard islands, would be successful.  This was our second option, the first one, which meant flying over the Austfonna glacier, had to be postponed by one day owing to prohibitive wind conditions.

Nevertheless, this additional day was going to be used by the ground team of scientists from University of Oslo and Norwegian Polar Institute to mount a number of corner reflectors that are used as control points for the airborne measurements.

Sea ice

We arrived at the airport around mid-afternoon and, after having checked that all the instruments were working as expected, we took off.

The measurements today consisted of sea-ice elevation mapping using the ASIRAS radar and laser scanner altimetry. In addition, we gathered our position and attitude information with GPS and inertial navigation systems. Also, a downward looking camera is used for visual inspection of the ice conditions.

After leaving the airfield, we headed north, flying above the Wijde Fiord which was partly covered by fast sea-ice. On the right, a number of outlet glaciers attracted our attention. The shadows inside the crevasses and the reflection of the Sun over the white and blue ice were spectacular.

As soon as we left the northern coast, the sea-ice disappeared. This was expected since the latest news on wind direction, suggested that the ice had moved towards the northwest. In fact, the ice was there, waiting for us eight nautical miles north.

We noted areas where the sea ice was rather compact and other zones, where large sections of floating ice were interleaved by narrow winding water leads that resembled land rivers.

We navigated over one planned CryoSat track for almost 200 miles in the ascending direction up to 82.5° N. After one-hour, we flew over the same track but in the opposite direction. We ‘rendezvoused’ with the satellite half-way through and we were happy to be informed that both space and ground systems had acquired that segment successfully.

Sea ice

Before landing at the airport, Henriette and Sine suggested performing two passes over the runway at an altitude of about 1000 feet to cross-calibrated the laser and ASIRAS. The pilots and airport traffic control consented.

We safely landed just in time before it started to snow.

It was another successful campaign day and this could only be achieved thanks to the skills of colleagues and pilots who plan and execute these activities in totally safe conditions.

But this time, we did not see any polar bears!