Greenland’s ice sheet has been known as the Earth’s Climate Archive for many years. From the numerous ice cores, researchers have already gained a lot of knowledge about the climate of the past. This could also be used to make predictions about the future course of the global climate. But now a new project wants to go a new way to find out when and how quickly the ice sheet disappeared completely the last time. For this purpose, however, the scientists do not examine the ice, but the bedrock under the ice sheet.
From next year on, the project, called “GreenDrill”, aims to try to drill the bedrock under the ice and take samples at four different locations in the north of Greenland. The idea is to use geochemical analysis and radioactive clocks to determine when the rock was exposed to air the last time. This would be a way of determining how quickly the ice sheet actually melts away, which in turn benefits the climate models. The team also hopes to show whether Greenland’s north will actually become the new hotspot for ice melt. “The whole bedrock is an archive,” explains Jörg Schaefer of Columbia University, assistant leader of the project. “It’s just a question of getting these freaking samples under the ice.”
The project will not drill through the thickest spots of the ice sheet to get to the rock, but will drill into the rock along the four locations along a line towards the coast at 300 meters, 100 and on the bare rock. The samples will then be tested for radioactive isotopes that can be used to create a clock. Because when cosmic rays hit rock, traces of a such isotopes are produced. Since ice blocks the radiation, the rate of decay of the isotope can be used to calculate the last time the rock had some “fresh air”. In this way, it is possible to determine indirectly how quickly the ice had formed and retreated. This is important for northern Greenland, as climate scientists suspect the next hotspot where ice could be particularly strongly affected by global warming. The researchers also hope to learn more about when and how quickly Greenland’s ice sheet melted down for the last time, allowing conclusions to be drawn about sea level rise.
A side aspect that the researchers want to explore as part of their project is the Hiawatha crater on the north-west coast of the island. Here the impact of a meteorite is suspected, but it’s not known for certain about the timing. But the meteorite could be responsible for a phenomenon known as “Young Dryas,” a cooling of the global climate about 13,000 years ago. Investigations of the rock under the ice near the crater could provide clues as to the age of the crater and the extent of the impact, thus solving yet another mystery hidden under Greenland’s ice sheet…. like so many others.
Dr Michael Wenger, PolarJournal
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