ARCTIC15 Field Campaign
ARCTIC15 is a campaign promoted by the Microwaves and Radar Institute of the German Aerospace Center (DLR), carried out in cooperation with ETH Zurich and with the support of the Alfred Wegener Institute (AWI). It takes place in Greenland from mid-April to the end of May 2015 with the objective of collecting polarimetric-interferometric SAR data at different frequencies (X-, C-, S-, L- and P-band) over different facies of the ice sheet. The measurements are performed using DLR's airborne F-SAR sensor. In total, the activities involve five test sites and include the collection of ground measurements, like ground penetrating radar (GPR) profiles and snow and firn stratigraphy, as well as the installation of GPS stations and corner reflectors for the calibration of the SAR acquisitions.##markend##
Accomplishing a campaign like ARCTIC15 requires big efforts in terms of costs to bear and energy to spend – efforts that are worth it for an extremely challenging objective: understanding the dynamics of Greenland and how they are related to climate change. Indeed, the Arctic and, in general, the cryosphere are particularly sensitive to temperature fluctuations. The primary effect of global warming is the variation in snow and ice cover which, in turn, affects air temperature, sea level and ocean currents. Moreover, the presence of snow and ice is a controlling factor of the Earth’s surface temperature as they reflect back most of the incoming solar radiation, avoiding further heating.
With the ARCTIC15 campaign, we aim to acquire a deeper understanding of SAR measurements from the different facies of Greenland and to develop innovative techniques for the extraction of glaciological parameters on a large scale with high spatial resolution. For this, electromagnetic models are being developed at both DLR and ETH, to gain a physical understanding of the interaction of the radar signal with surface and subsurface features determining the SAR measurements at the different test sites.
Installation phase was a true success
During the planning of the ARCTIC15 campaign, we always told ourselves not to expect everything to work out perfectly. We thought: there will be at least one test site where we will be unable to install the corner reflectors due to weather, risky landing conditions or all the other smaller and bigger things that can go wrong on a field campaign. But in the end, we managed to prepare all five test sites successfully!
The flights with the Twin Otter of Kenn Borek Air were already a complete success on their own. We reached four test sites within five days, installed the corner reflectors and conducted all the measurements as planned. At South Dome, our highest test site, we had such good conditions at -22 degrees Celsius, low winds, good visibility and a hard packed snow surface, that we were even able to place corner reflectors as far as one kilometre away from our landing spot. At the Dye-3 test site, however, the 30 knot and over wind caused a strong snow drift and visibility below 250 metres. Fully relying on compass and GPS to make our way back to the aircraft, we had to limit the distances we covered to about 600 metres.
After this success, the biggest challenge remained at the last test site, which stretches from the edge of Russel Glacier, 25 kilometres onto the ice cap and is aligned with the so-called K-Transect. After a two-day delay due to the weather conditions, we finally took off from Kangerlussuaq with the big Sikorsky S61 helicopter of Air Greenland. During a short, spectacular flight about 15 minutes later, we were able to see the challenging conditions with our own eyes.
The first part of the test site was covered by incredibly huge and deep crevasses, which made a landing impossible. The second part was still too rugged for the Sikorsky. It needs a flat area to stand on its wheels, and crevasses filled with fresh snow are quite a bad choice. Three failed landing attempts later, we had to initiate our backup plan and land on solid ground just next to the glacier's edge. There, the corner reflectors are still well within our planned radar acquisitions strip and are even accessible by all-terrain vehicles. Despite being a bit unhappy about having no reflectors on the glacier at this test site, it was also a relief to not have to take the risk of walking around in such a heavily crevassed area, even though we were well prepared for this by Silvan, our expert in all mountaineering related topics.Now that all test sites are successfully prepared, the work begins for the F-SAR team who already began conducting SAR acquisitions. More information about this will come in the next blog entry.
It was an incredible experience to work in such a remote and harsh environment! Thanks to Martin and Silvan for being such a great team.