Glaciers in Antarctica turn the concept of “glacier tempo” on its head. A new study of an area rarely observed on the continent boils down to the fact that rising heat causes ice flows to flow faster, which has worrying consequences for sea level rise.
The study, published in Nature Communications this week, 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 that this region is accelerating across long multidadal time scales,” lead author Heather Selley said in an email. “We can only examine the physical process that causes change with detailed maps of where changes are taking place.”
Selley explained that scientists had previously observed changes in the ice level in the Getz region, but that they could not be sure due to atmospheric processes, such as less snowfall or melting ice on the surface, or changes in ice speed. The latter is driven by warmer seawater that underlies floating ice, indicating worrying effects of climate change. The new study allows scientists to link prolonged ocean warming more concretely to the changes in the ice shelf.
The results are pretty jerky. The speed of the 14 glaciers surveyed increased by an average of almost 23% between 1994 and 2018. Three of the glaciers increased by more than 44%. A particularly fast ice flow moves 59% faster than it was two decades ago.
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Ice loss has also increased dramatically. The glaciers lost 315 gigatons of ice during that period – enough to fill 126 million Olympic-sized pools. And the loss has increased dramatically over the past few years. Between 1994 and 1999 and 2000 to 2009, the area lost 5.6 and 5.8 gigatons per year, respectively. But between 2010 and 2018, the rate of ice loss skyrocketed 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 in an area that is very important for understanding sea level rise, but relatively little is known about the region. Getz is not exactly on a list of tourist destinations for Antarctic voyages. It is so remote that no human has set foot in parts of the region, and nine of the 14 glaciers in the study are not even mentioned.
“There are only a handful of studies on Getz compared to hundreds on the Amundsen marine sector glaciers (Thwaites and Pine Island),” Selley noted. “This study shows that the percentage of Getz glaciers is comparable to the velocity measured on Thwaites and Pine Island, showing the importance of the Getz region in terms of the fastest changing glaciers in Antarctica.”
Thwaites and Pine Island are one of the most endangered glaciers in Antarctica. Researchers on a trip to Thwaites last year drilled and recorded in the floating section of the glacier direct observations warm seawater flowing beneath it. David Holland, a New York University glacier researcher who conducted the research, said in a press release at the time that it ‘suggests that it could undergo an unstoppable retreat that has major consequences for global sea level rise.’
The new findings exploring the Getz region are raising another source of concern. Antarctica has a major impact on the world’s sea level rise, and understanding how ice behaves on the continent is becoming increasingly important in determining how much sea level there may be. What’s more, ice racks collapsing in the region behave somewhat like corks leaping out of a bottle of wine, dropping an ice stream into the sea and creating more instability and melting in the region. The glaciers Thwaites and Pine Island, for example, are the cork on land ice that, if plowed into the ocean, can push the sea 3.1 meters or more. Paying closer attention to how little studied areas like Getz are doing will be important for preparing for the future.
“If we do not understand why changes occur, we can not model the change accurately,” Selley said. “This again means that we can not reliably predict the future ice loss and sea level contribution of Antarctica.”