![]() “And when ice shelves dwindle and weaken, the continent’s massive glaciers tend to speed up and increase the rate of global sea level rise.” “Antarctica is crumbling at its edges,” says JPL scientist Chad Greene, lead author of the calving study. Combined, the complementary reports provide the most complete view yet of how the frozen continent is changing. The other study, published recently in the journal Earth System Science Data, shows in unprecedented detail how the thinning of Antarctic ice as ocean water melts it has spread from the continent’s outward edges into its interior, almost doubling in the western parts of the ice sheet over the past decade. Ice loss from calving has weakened the ice shelves, allowing Antarctic glaciers to flow more rapidly to the ocean and accelerating the rate of global sea level rise. This surprising finding doubles previous estimates of ice loss from the Antarctic’s floating ice shelves since 1997, from 6 trillion to 12 trillion metric tons. The scientists found that the edge of the ice sheet has been shedding icebergs faster than the ice can be replaced. Story by Kathryn Hansen.One study, published recently in the journal Nature, maps how iceberg calving – the breaking off of ice from a glacier front – has changed the Antarctic coastline over the last 25 years. NASA Earth Observatory images by Lauren Dauphin, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview and Landsat data from the U.S. According to Shuman: “We have no solid idea what ‘normal’ really is for this unusual ice shelf.” These areas are stressed by storms and tides and thin as they are melted from above or below, ultimately making them more prone to forming rifts and breaking away.Īs for the “new” Brunt, it remains to be seen how the complex floating glacial ice responds to the most recent calving event. As glacial ice flows from land and spreads out over the sea, shelf areas farthest from shore grow thinner. The breaking (calving) of icebergs from ice shelves is part of a natural, cyclical process of growth and decay at the limits of Earth’s ice sheets. “The rapid formation of subsequent rifts-to long-standing Chasm 1 and 2-and recent calving to the northeast makes it clear that these shelf areas are dynamic with poorly understood stresses,” said Christopher Shuman, a University of Maryland, Baltimore County, glaciologist based at NASA’s Goddard Space Flight Center. The “new crack” in that image ultimately separated in February 2021 and formed Iceberg A-74. Notice several other cracks across the northeast part of the shelf. The second image, acquired with the Operational Land Imager (OLI) on Landsat 8, shows the extent of Chasm 1 on January 12, 2021, about two years prior to the break. Several factors may have contributed to the completion of the break, including a lack of sea ice to help resist, or “push back,” against the stresses on the shelf ice in 2023. That is, until the 2022–2023 Antarctic summer when the chasm sped up and ultimately broke past the McDonald Ice Rumples-a submerged knob of bedrock that served as a pinning point for this part of the shelf. It continued to lengthen for almost a decade, extending by as much as 4 kilometers (2.5 miles) per year in early 2019. This chasm started growing in the 1970s, followed by a period of dormancy, and then resumed growth in 2012. The break occurred along a rift known as Chasm 1. BAS reported that the station, which was relocated farther inland in 2016 as the chasm widened, was unaffected by the recent break. (For reference, the Antarctic Peninsula and its ice shelves are located on the opposite side of the Weddell.) The shelf has long been home to the British Antarctic Survey’s Halley Research Station, where scientists study Earth, atmospheric, and space weather processes. The glacial ice in the shelf flows away from the interior of Antarctica and floats on the eastern Weddell Sea. ![]() ![]() The berg is visible in this image, acquired on January 24, 2023, with the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. National Ice Center has named it Iceberg A-81. The question among scientists was not if the growing rift would finish traversing the shelf and break, but when? Now, nearly four years later, it has done just that.Īccording to the British Antarctic Survey (BAS), the break occurred late on January 22, 2023, and produced a new iceberg with an area of 1550 square kilometers (about 600 square miles). In February 2019, a rift spanning most of the Brunt Ice Shelf in Antarctica appeared ready to spawn an iceberg about twice the size of New York City. ![]()
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