Flooded radar – instruments in extreme conditions
During the iGRIFF2017 expedition in summer 2017, part of the first phase of GROCE, four radar instruments have been deployed on the floating tongue of 79N Glacier. Since then, the instruments were running almost continuously, acquiring data from which we can estimate the melt rate at the lower side of the ice, the one in contact with the ocean. In early July 2022, Angelika Humbert and Matthias Braun visited these instruments in a one day operation, servicing them with new batteries and harvesting data.
What changes have you observed in the environment surrounding the instruments since 2017?
Very impressive was the change in surface condition since the deployment of the instruments. At that time the surface was more or less even and the nearest melt lake or river some hundred meters away. During these five years, they moved with the glacier through the ablation zone, which is the part of the glacier where the surface melt is greater than the snow accumulation. The glacier experienced some massive summer melt, so that rivers and lakes are now in their direct vicinity. One of the instruments did not survive that. While it sent regular emails until end of June that all is ok, just before our visit it drowned. The electronic did not survive this, but the memory cards still contain all data! We were really lucky that we arrived only few days later. The other instruments were either upside down or tipped over, but we were able to get them a quick makeover and get them running again – as long as it will be possible in such extreme conditions. Now we are very curious to see what we will learn from the processed data.
So, why are these stations so important?
These stations are now almost long term observatories and they enable us to measure for the first time the change in basal melt rates over longer time periods. However, to revisit the same positions and have comparable observations, the stations need to be moved back to their original position. This requires unfortunately more time and fuel then we had available this year and not least lots and lots of luck with weather.