Antarctic glaciers return to the concept of “glacial rhythm”. A new study of a little-observed area on the continent finds that rising heat causes ice flows to flow faster, which has worrying consequences for rising sea levels.
study, published this week in Nature Communications, uses a quarter of a century of satellite recordings 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 periods of multidecades,” lead author Heather Selley said in an e-mail. “Only with detailed maps of where changes occur can we investigate the physical process that causes the change.”
Selley explained that although scientists had previously observed changes in ice levels in the Getz region, they could not be sure if it was due to atmospheric processes, such as fewer snowfalls or melting surface ice or changes in ice speed. The latter is driven by warmer ocean waters that lower floating ice and indicate worrying impacts due to climate change. The new study allows scientists to more specifically link long-term global warming to ice shelf changes.
The results are quite impressive. The speed of the 14 glaciers surveyed increased by an average of almost 23% between 1994 and 2018. Three of these glaciers increased by over 44%. A particularly fast flow of ice was moving 59% faster than it was two decades ago.
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Ice losses have also increased dramatically. Glaciers lost 315 gigatons of ice – enough to fill 126 million Olympic pools – in that period. And the loss has accelerated dramatically in recent years. Between 1994 and 1999 and 2000 until 2009, the area lost 5.6 and 5.8 gigatonnes per year, respectively. But between 2010 and 2018, the rate of ice loss increased to 24.8 gigatons of ice loss per year. This huge loss is responsible only 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 massive importance for understanding sea level rise, but relatively little is known about the region. Getz is not exactly on the list of tourist destinations for cruises in Antarctica. It is so far away that no one has set foot in parts of the region and nine of the 14 glaciers in the study are not even named.
“There are only a handful of studies on Getz compared to hundreds of glaciers in the Amundsen Sea (Thwaites and Pine Islands),” Selley said. “This study shows that the percentage of acceleration of the Getz Glaciers is comparable to the speed measured on the island of Thwaites and Pine, showing the importance of the Getz region in relation to the fastest changing glaciers in Antarctica.”
Thwaites and Pine Island are among the most endangered glaciers in Antarctica. Researchers on a trip to Thwaites last year drilled into the floating part of the glacier and recorded direct observations of warm sea water flowing below. David Holland, a glaciologist at New York University who conducted the research, SAPS in a press release at the time, “suggests that it could be subjected to an unstoppable retreat that has huge implications for rising sea levels globally”.
New findings on the Getz region add another level of concern. Antarctica has a major impact on rising sea levels, and understanding how the ice behaves on the continent is becoming increasingly crucial to finding out how much we could raise sea levels. Moreover, ice shelves collapsing in the region behave somewhat like corks coming out of a wine bottle, releasing a torrent of ice into the sea and creating more instability and melting in the region. Thwaites and Pine Island glaciers, for example, are the ice stopper on land that, if thrown into the ocean, could push the seas 10 feet (3.1 meters) or more. Increased attention to how little is studied in areas such as Getz will be important in preparing for the future.
“If we don’t understand why change is happening, then we can’t model change exactly,” Selley said. “This, in turn, means we can’t reliably predict future ice loss and sea level contribution in Antarctica.”