Glaciers in Antarctica are turning the concept of “glacial pace” on its head. A new study of a little-observed area on the continent finds that rising heat is making ice streams flow faster, which has worrisome consequences for sea level rise.
The study, published this week in Nature Communications, uses a quarter century of satellite records to observe changes in the Getz Ice Shelf in western Antarctica. The study “is the first to show this region is speeding up over long multidecadal timescales,” lead author Heather Selley said over email. “It’s only with detailed maps of where changes are occurring that we can investigate the physical process driving change.”
Selley explained that while scientists had previously observed changes to the level of ice in the Getz region, they couldn’t be sure if it was because of atmospheric processes, like less snowfall or surface ice melt, or changes in ice speed. The latter is driven by warmer ocean water undercutting floating ice, and points to worrying impacts from climate change. The new study allows scientists to more concretely tie long-term ocean warming to the changes in the ice shelf.
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The results are pretty jaw-dropping. The speed of the 14 glaciers surveyed increased by an average of almost 23% between 1994 and 2018. Three of those glaciers sped up by more than 44%. One particularly speedy ice flow was moving 59% faster than it was two decades ago.
Ice loss also increased dramatically. The glaciers lost 315 gigatonnes of ice — enough to fill 126 million Olympic swimming pools — during that time period. And the loss 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, the rate of ice loss skyrocketed to 24.8 gigatonnes of ice loss per year. This huge loss is responsible for just more than 10% of the Antarctic’s total contribution to sea level rise since the early 1990s.
The Getz Ice Shelf is in an area of massive importance for understanding sea level rise, but comparatively 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 portions of the region, and nine of the 14 glaciers in the study aren’t even named.
“There are only a handful of studies on Getz compared to hundreds on the Amundsen Sea Sector glaciers (Thwaites and Pine Island),” Selley noted. “This study shows that the percentage speedup of the Getz glaciers is comparable to the speedup measured on Thwaites and Pine Island, showing the importance of the Getz region relative to the most rapidly changing glaciers in Antarctica.”
Thwaites and Pine Island are among the most imperiled glaciers in Antarctica. Researchers on a trip to Thwaites last year drilled into the floating portion of the glacier, and recorded direct observations of warm seawater flowing underneath. David Holland, a glaciologist from New York University who performed the research, said in a press release at the time that it “suggests that it may be undergoing an unstoppable retreat that has huge implications for global sea level rise.”
The new findings looking at the Getz region add another layer of concern. Antarctica has a big impact on the world’s sea level rise, and understanding how ice behaves on the continent is becoming increasingly crucial to figuring out just how much sea level rise we might be in for. What’s more, ice shelves collapsing in the region behave somewhat like corks popping out of a bottle of wine, releasing a torrent of ice into the sea and creating more instability and melt in the region. The Thwaites and Pine Island glaciers, for example, are the cork on land ice that, if plopped in the ocean, could push seas 3.1 metres or more higher. Paying closer attention to how little-studied areas like Getz are faring will be important for preparing for the future.
“If we don’t understand why changes are occurring, then we can’t accurately model the change,” Selley said. “This in turn means we can’t reliably predict future ice loss and sea level contribution from Antarctica.”