Natural and societal consequences of climate-forced changes of Jostedalsbreen Ice Cap
Successful test of airborne ice radar at Nigardsbreen and five other outlet glaciers
by Jostein Bakke, March 29, 2022
During the JOSTICE 2022 spring field campaign, a newly developed airborne ice radar was applied to collect data on ice thicknesses from several outlet glaciers. The results are promising and will provide opportunities for collecting valuable data from otherwise inaccessible areas of Jostedalsbreen Ice Cap.
For over a year, members of the JOSTICE project have planned a new set up for airborne ice radar surveys together with Laurent Mingo in Blue Systems Integration. To get a complete picture of the subglacial terrain below Jostedalsbreen Ice Cap for ice modelling, it is needed to use helicopter to survey steep and heavily crevassed areas. Based on the experiences from a similar pilot project in Canada and Blue Systems Integration, we have further developed a platform and antenna set up.
The airborne radar is hanging 40 m below the helicopter in a long line that can be released by the pilot in case of an emergency. The red balloons are for making soft landing when the pilot sets the platform down (photo: Jostein Bakke).
Together with a local carpenter in Bergen we have constructed a platform that can be transported on a trailer and mounted together in approximately one hour. To hold the antennas, we use telescopic rods made in a very stiff composite material used for window washing. This makes it possible to adjust the length depending on the antenna frequency we are using. For the test we equipped the platform with a 5 MHz antenna, which gives approximately 10 MHz on the ground due to the extra distance to the ice surface. Key for being able to do helicopter operations in often challenging light conditions over a glacier is a precise height sensor that can guide the pilot and make it possible to keep constant elevation above the ground. For this purpose, we installed a very accurate AGL system with wireless transfer to the cockpit and a display for the pilot. During surveying the platform should be as close as possible to 30 m above the ice, and it is with our current transmitter possible to fly at a speed of 20 knots.
Cockpit with some extra instruments for the pilot and his helper. We used an iPad with the app Field Maps for navigating along the profiles. To the lower left you can see the wireless display showing the distance from the platform to the ground (photo: Jostein Bakke).
The results were very promising, and after some processing we got a very clear signal identifying the bedrock below the ice down to approximately 400 m of ice. After flying above Nigardsbreen, Fåberstølsbreen, Lodalsbreen, Erdalsbreen and Småttene in two hours, the approach has proved its efficiency! The successful test of the platform and the radar setup opens new avenues for surveying ice in remote areas. It is also possible to carry higher frequency antennas for snow depths to supplement traditional snowpack measurements. Now we are ready to do more work on Jostedalsbreen Ice Cap, if the weather allows it during the spring.
Ice radar profile along the centreline of Nigardsbreen towards the top. The bedrock reflector can be seen very clear for most of the profile.
Shadow of the setup over Nigardsbreen (photo: Jostein Bakke).