1 November 2018

A field trip to the centre of the Greenland ice sheet to recover ice for analysis.

Firn air sampling expedition to Greenland

For more than two decades our lab has analyzed air from the layer of compressed snow, called firn, that covers polar ice sheets. This year I could finally join a field campaign to the Greenland ice sheet myself.

The trip there took longer than expected, because of a very warm period in Greenland in the beginning of June. The snow at the East Greenland Ice-Core Project (EGRIP) camp was so soft that the heavy Hercules C130 cargo aircraft would not be able to take off after landing. So, we were stuck for four days in Kangerlussuaq west Greenland. We spent the time packing and preparing, but also made a very nice trip to the Russel glacier.

After four days we finally boarded the aircraft. After crossing a mountainous landscape with lakes, glaciers and snow, we reached the flat, white interior ice sheet. The snow is so bright that even from the aircraft you had to put on sunglasses to see. After 2 hours we reached EGRIP camp (75.63ºN, -35.99ºW), with beautiful weather and a temperature of about -12 ºC. It was an impressive moment to move into the camp that would be my home for the next two weeks. It is the only human settlement for several hundred kilometers in any direction – on top of a 2500 m thick layer of ice. The dominating structure is the EGRIP dome, where you eat and most of the social life takes place. Most of the camp crew members sleep in smaller tents. I shared a tent with Thomas Blunier from Copenhagen and Johannes Freitag from Bremerhaven.

Clockwise from top: Trip to the Russel glacier with former IMAU master student Ernst Jan Kuiper (left), EGRIP Dome; Transport of equipment (left) and setup of the firn drilling site (right); Firn air drilling (left) and the first IMAU sample container.

After arranging our personal stuff we started bringing our scientific equipment to the firn air drilling site about 2 km away from the main camp. This was hard work, but also fun because of many rides with the snow mobiles.

We quickly set up the camp and started drilling already on the second day. To take air samples from the firn, you first have to drill a hole. Then you insert a 5-m long rubber “bladder”, inflate it like the inner bicycle tube so that it seals off the hole, after which you can pump air from below the bladder out of the snow and collect it for analysis. The deeper you get, the older the air that is extracted: at this location the age is about 40 years at the bottom of the firn layer.

For the next two weeks we sampled air until we reached the firn-ice transition at about 65 m depth, where the porosity of the firn becomes too low to extract air samples. We collected a total of 170 air samples for 8 different groups around the world.

It was hard work, but also an unforgettable experience. So many things are different on the ice. Sleeping in tents under these hostile conditions (including having to go to the bathroom – a hole in the ice – at -30°C in the middle of the night), having to melt ice to create your own drinking water, being exposed to the cold and the wind are only some examples. I will never forget the famous Saturday-night parties in the EGRIP Dome, the midsummer celebration under the midnight sun and the fantastic team spirit. If you want to know more, see my blog at https://egrip2018tr.sites.uu.nl/.

Thomas Röckmann