Glaciers in Antarctica are turning the concept of ‘glacial pace’ on its head. A new study of a little-observed area on the continent shows that rising heat is accelerating ice currents, which has alarming consequences for sea level rise.
The study, published this week in Nature Communications, uses a quarter of a century of satellite records to observe changes in the Getz Ice Shelf in western Antarctica. The study “is the first to show that this region is accelerating over long, multidecadal timescales,” lead author Heather Selley said via email. “Only with detailed maps of where changes are taking place can we explore the physical process that leads to change.”
Selley explained that while scientists had previously observed changes in the ice level in the Getz region, they couldn’t be sure if this was due to atmospheric processes, such as less snowfall or melting surface ice, or changes in the ice speed. The latter is driven by warmer ocean waters that are undermining floating ice and points to worrying consequences of climate change. The new study allows scientists to more concretely link long-term ocean warming to the changes in the ice shelf.
The results are quite overwhelming. The speed of the 14 glaciers studied increased by an average of almost 23% between 1994 and 2018. Three of those glaciers accelerated more than 44%. A very fast ice flow was moving 59% faster than two decades ago.
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Ice loss also increased dramatically. The glaciers lost 315 gigatons of ice during that period – enough to fill 126 million Olympic swimming pools. And the loss has accelerated dramatically in recent years. Between 1994 and 1999 and 2000 to 2009, the area lost 5.6 and 5.8 gigatonnes per year respectively. But between 2010 and 2018, ice loss soared to 24.8 gigatons of ice loss per year. This huge loss is responsible for just over 10% of Antarctica’s total contribution to sea level rise since the early 1990s.
The Getz Ice Shelf is located in an area of immense importance for understanding sea level rise, but relatively little is known about the region. Getz isn’t exactly on a list of tourist destinations for Antarctic cruises. It’s so remote that no humans have set foot in parts of the region, and nine of the 14 glaciers in the study haven’t even been named.
“There are only a handful of studies on Getz compared to hundreds on the glaciers of the Amundsen Sea Sector (Thwaites and Pine Island),” noted Selley. “This study shows that the percent acceleration of the Getz glaciers is comparable to the speed measured on Thwaites and Pine Island, demonstrating the importance of the Getz region in relation to the fastest-changing glaciers in Antarctica.”
Thwaites and Pine Island are among Antarctica’s most endangered glaciers. Researchers who traveled to Thwaites last year drilled into the floating portion of the glacier and recorded direct observations of warm seawater flowing underneath. David Holland, a New York University glaciologist who conducted the study, said in a press release at the time that it “suggests it is undergoing an unstoppable retreat that will have huge implications for global sea level rise.”
The new findings regarding the Getz region add another cause for concern. Antarctica has a major impact on sea level rise in the world, and it is increasingly important to understand how ice behaves on the continent to figure out how much sea level rise we could expect. Additionally, ice shelves collapsing in the region behave somewhat like corks coming out of a bottle of wine, releasing a torrent of ice into the sea and causing more instability and melting in the region. For example, the glaciers of Thwaites and Pine Island are the cork on land ice that, if crushed into the ocean, can push the seas 10 feet (3.1 meters) or more higherPaying more attention to how little-studied areas like Getz are doing will be important for preparing for the future.
“If we don’t understand why changes are happening, we can’t model the change accurately,” Selley said. “This, in turn, means that we cannot reliably predict future ice loss and sea level contribution from Antarctica.”