Significant sea level rise expected after ice shelves collapse

The Larsen C and George VI are not the names of noble wooden ships or kings of old, rather, they are the identifiers of two Antarctic ice shelves that are currently at risk of collapsing. The Larsen C was in the news last summer due to its break-away from a trillion-ton iceberg, and its collapse would contribute roughly a few millimeters to sea-level rise. But the break-up of the smaller George VI Ice Shelf would actually have a much larger impact, according to new research published in the European Geosciences Union journal The Cryosphere.

Because both of these large ice platforms are holding back inland glaciers, their collapse would mean that the ice carried by these glaciers could flow faster into the sea, contributing to sea-level rise. Using computer models to simulate the interactions between the Antarctic Peninsula ice sheet and ice shelves, the researchers have found that collapse of the Larsen C would result in inland ice contributing about 4 mm to sea level, while collapse of the George VI could potentially lead to 22 mm in global sea level rise due to glacial response.

“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,” says study-author Nicholas Barrand, a glaciologist at the University of Birmingham in the UK.

“Taken together with these other sources, the impacts could be significant to island nations and coastal populations. The Antarctic Peninsula may be seen as a bellwether for changes in the much larger East and West Antarctic ice sheets as climate warming extends south.”

In 2002, warming on the Antarctic Peninsula led to the collapse of the Larsen B – an ice shelf just north of Larsen C. After being stable for the last 10,000 years, this entire ice shelf broke up in a period of time just over two weeks.

“Larsen C is the most northerly remaining large ice shelf, therefore subject to the warmest temperatures, and the likeliest candidate for future collapse,” says lead-author Clemens Schannwell, who conducted the work while at the University of Birmingham and the British Antarctic Survey. “George VI is further west and south, in a slightly cooler climate, but is still vulnerable to a warming atmosphere and ocean.”

Worth noting is the fact that the sea level rise predicted by the researchers’ models would not occur until around the year 2300. “In light of the increasing temperatures projected for the coming century, the Antarctic Peninsula provides an ideal laboratory to research changes in the integrity of floating ice shelves,” says Barrand.

“This region can tell us about ice shelf processes and allow us to observe the response of inland ice to ice-shelf changes. We should view these dramatic changes in the Antarctic Peninsula as a warning signal for the much larger ice sheet-ice shelf systems elsewhere in Antarctica with even greater potential for global sea-level rise.”

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By Connor Ertz, Earth.com Staff Writer

Image Credit: British Antarctic Survey