Antarctic Ice Sheet could begin melting sooner than expected

The East Antarctic Ice Sheet may not be as stable as scientists believed. Image: Shutterstock

The East Antarctic Ice Sheet could raise global sea levels by up to 60 metres if it melts.

The East Antarctic Ice Sheet has long believed to be stable, thanks to the below freezing temperatures, and therefore unlikely to contribute greatly to rising sea levels over the next few centuries. But a recent study of ice sheet response to climate warming 20,000 years ago and the subsequent rise in sea levels suggest that the ice sheet may respond more rapidly to climate change than previously expected.

Dr Duanne White and Associate Professor Damian Gore of Macquarie University and Dr David Fink of the Australian Nuclear Science and Technology Organisation (ANSTO) conducted a study of the outlet glaciers, which transport the snow that falls on the ice sheet to the sea. White stated in the press release “These outlet glaciers can quickly move ice from the ice sheet to the coast through these basins and are thus a strong linkage between the ice sheet and the ocean, providing a means of more rapidly transferring changes in oceanic and atmospheric conditions to changes in the size of the ice sheet than would otherwise be expected.”

The research team investigated the changes in ice sheet elevation in the Lambert Glacier-Amery Ice Shelf region, which is estimated to drain 15 percent of East Antarctica’s ice, to see how it had reacted to past climate and sea level changes. They spent three summers in Antarctica, collecting samples from boulders that had been deposited on the mountain ranges by ice during periods of higher elevation.

The samples were then tested for rare isotopes that act as nuclear clocks using a new technique called cosmogenic surface exposure dating. The isotopes are produced as the boulders are bombarded with high energy cosmic rays though the atmosphere, allowing the researchers to determine when the boulders were released from the ice and correlating age with altitude to see how far the ice retreated.

The results indicate that these ice stream regions are more sensitive to climate change than previously believed. The ice thickness in Lambert Glacier ice streaming region began to decrease earlier than expected at the end of the last Ice Age and there was a reduced delay between climate change and changes in ice thickness further inland.

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