Underwater curtain to protect Greenland ice sheet | Polarjournal
The idea sounds simple: A curtain should prevent too much warm water from reaching the ice edge along the bottom and melting the ice from below. At the same time, however, the curtain should be flexible enough to allow icebergs from the glacier to drift out. Image: Arctic Center, University Lapland

It is now an undisputed fact that the Greenland ice sheet, the second largest mass of ice in the world, is slowly but surely melting away. In the process, the ice is attacked from two sides by global warming. Especially from the ocean side, where warmer deep water reaches their edges and the glaciers that form the outflow of the ice sheet melt from below. A project group now wants to implement an idea to reduce this process and is calling on stakeholders from different branches to get involved.

The “Iron Curtain,” which had separated Eastern Europe from Western states for decades, was intended to prevent Western ideas and values from crossing over and undermining and eroding the Communist East. Professor John Moore of the Arctic Center at the University of Lapland now has a much more positive idea: a curtain to protect the Greenland (and later also the Antarctic) ice sheet at its most vulnerable points, namely at the glacier edges, from eroding by warm deep water. In order to make this idea a reality, a seminar was held on the side of the Arctic Circle meeting in Reykjavik, where various stakeholders were able to learn about the idea and engage in a first exchange. The goal is to get scientists, engineers, economists, politicians, and especially Inuit representatives around the table and take the project to the next level, which is the formation of an advisory board.

Ocean-terminating glaciers have the problem that they melt not only from above due to warm air masses and solar radiation, but also from below as they float on the water. This is because, due to global warming, warmer water at depth now reaches the fjords of the glaciers with the ocean currents. This warmer water mass does not mix with the slightly less saline surface water above, which would be colder and also contain many nutrients from the glacier. The warmer deep water flows to below the glacier and slowly melts the ice from below. This causes the edge of the glacier to become unstable, ice breaks off and floats out of the fjord as an iceberg. The more warm water that gets under the glacier, the faster it retreats. As climate change has caused the oceans to warm more and more in recent decades, this heat has also reached the depths and is now driving the melting of glaciers worldwide there as well.

For the time being, the idea is to be implemented at Sermeq Kujalleq, which most people know as the Jakobshavn glacier near Ilulissat. Most of the Greenland ice sheet is currently flowing out of this glacier and it is one of the fastest retreating glaciers on the island. A special feature on the seabed will help the idea of the curtain. This is because at the entrance between the Ilulissat Ice Fjord, at the end of which the glacier lies, and the large Disko Bay in front of it, there is a sill on the seabed which, like a barrier, keeps the slightly warmer deep water from the Atlantic, flowing along the bottom, from pouring completely into the deeper basin of the fjord behind it. According to Moore’s idea, a curtain is now to be anchored on this threshold, which will further raise the threshold for the warm water and thus provide for a further reduction of the warm water. This should reduce further melting of the glacier and ice loss from the ice sheet, John Moore is convinced.

Disko Bay is one of the most productive regions in West Greenland, mainly due to the nutrient-rich water that pours into the bay between the warmer deep water and the colder surface water from the glacier. This nutrient transport must be maintained so as not to deprive local fishermen of their livelihood. Photo: Heiner Kubny

At the same time, however, water exchange and also the drifting of icebergs out of the fjord should be possible. This is because the water from the glacier is rich in nutrients, making Disko Bay a region rich in fish. That’s why Moore and his colleague Ilona Mettiäinen also want a broad coalition of diverse stakeholders in the proposed project. Mettiläinen has had many discussions with local fishermen and associations in advance to have their support and knowledge of the conditions with them in the project. “Basically, the project stands for sustainability and local acceptance of ice sheet protection,” says Ilona Mettiläinen.

Moore’s proposal is one of several ideas for geoengineering to help reduce or even stop the effects of climate change on the Arctic. Such proposals have been discussed again and again for several years now, and most of the time they fail due to costs, feasibility, or previously unknown factors and influences. In a paper in the journal Nature, Moore himself and colleagues had suggested building a wall of sand and sediment in front of the same glacier to retain the warm water. About 0.1 cubic kilometers of sand and gravel plus concrete for stabilization would have been necessary, according to the article. The new idea has found a receptive ear among geoengineering experts, such as Aker Solutions, which participated in the seminar. “This is a great opportunity to challenge our brightest minds in close collaboration with leading scientists in the field,” says Aker Vice President Marianne Hagen. And John Moore is convinced that, on the one hand, the project can help Greenland lead the way in managing global sea level rise. On the other hand, it could also help solve the problem in Antarctica if it works in Greenland. A curtain, then, that for once nevertheless connects through separation.

Dr Michael Wenger, PolarJournal

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