Researchers Reveal How High Sea Levels Will Rise If Two Major Antarctic Ice Sheets Melt

The George VI Ice Shelf could contribute significantly to global sea level rise over the next few hundred years. British Antarctic Survey

An international team of researchers has put a figure on how much seas would rise following the collapse of two Antarctic ice shelves. Oddly enough, the trillion-tonne headline-grabbing Larsen C iceberg would contribute just a few millimeters, whereas the smaller George VI ice shelf would have a much larger impact.  

Published in the European Geosciences Union journal The Cryosphere, the study suggests that the collapse of George VI would cause sea levels to rise around 22 millimeters by 2300 – as much as five times the rise caused by the collapse of Larsen C (4 millimeters). The two ice shelves are considered to have the highest risk of collapse as rapid warming in the Antarctic Peninsula continues to threaten the region. These two ice sheets hold back inland glaciers whose ice would break off and flow faster into the sea if the ice shelves were to collapse.  

"These numbers, while not enormous in themselves, are only one part of a larger sea-level budget including loss from other glaciers around the world and from the Greenland, East and West Antarctic ice sheets," explained study author Nicholas Barrand, a glaciologist at the University of Birmingham in the UK, in a statement. "Taken together with these other sources, the impacts could be significant to island nations and coastal populations." 

Rift propagation along the Larsen C Ice Shelf. This rift, which led to the calving of an iceberg twice the size of Luxembourg last year, raised questions about the future stability of the Larsen C Ice Shelf in a warming world. British Antarctic Survey

Using computer models to simulate interactions between the ice sheets and shelves, the team suggests the glaciers responding to Larsen C would add up to 2.5 millimeters to oceans by 2100 and 4.2 millimeters by 2300. But the George VI Ice Shelf is much more vulnerable because of its location. At 24,000 square kilometers (9,270 square miles), it is roughly half the size of Larsen C, but because it is fed by glaciers and holds back draining ice, it could contribute up to 8 millimeters by 2100 and 22 millimeters by 2300.

"Prior to our work, we didn't know what would happen to the upstream ice in the Antarctic Peninsula if these shelves were to be lost," said lead author Clemens Schannwell. "This could have important implications for the local environment and for global sea levels, information that is essential for climate-change mitigation planning and policy." 

Another study earlier this year shed light on just how much ice is being lost in Antarctica. In the last 25 years, the world’s largest ice sheet has lost almost 3 trillion tonnes (3.3 trillion tons) of ice, contributing to an almost 8-millimeter rise in global sea level.

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