Antarctica’s once-massive Larsen B Ice Shelf is melting rapidly, and will likely be entirely gone by the end of this decade, according to a new report from NASA. In 2002, NASA released dramatic images that showed a portion of Antarctica’s Larsen B ice shelf collapse and disappear. “Although it’s fascinating scientifically to have a front-row seat to watch the ice shelf becoming unstable and breaking up, it’s bad news for our planet. This ice shelf has existed for at least 10,000 years, and soon it will be gone,” said Ala Khazendar of NASA’s Jet Propulsion Laboratory, who led the study.
The data for the study was collected by aircraft measuring ice surface elevations and bedrock depths and space-based “synthetic aperture radars” that have been operating since 1997. The Larsen B ice shelf is currently 625 square miles in area and 1,640 ft at its thickest point. The studies have shown that two of the three glaciers feeding Larsen B have sped up markedly since the shelf split in 2002, with scientists now predicting that a major crack is likely to move all the way across the shelf, splintering the remnants into icebergs that will float away. “These are warning signs that the remnant is disintegrating,” said Ala Khazendar. During the collapse of 2002, a total of about 3,250 square kilometers of shelf area melted within 35 days.
For thousands of years, this system was roughly stable. Ice would flow gradually into the oceans. But this was all counterbalanced by snow that was falling back on top of Antarctica and replenishing the ice sheets. Over the last two decades, however, that’s changed. As global warming has progressed, Antarctica’s ice sheets are now losing 147 gigatons of ice each year, mainly from the Amundsen Sea sector of West Antarctica. The system is no longer in balance, and Antarctica’s ice is flowing more quickly into the ocean than before. In fact, Antarctica’s ice shelves have thinned by up to 18% in the last 18 years. Scientists watched the Larsen A Ice Shelf collapse in 1995. Then the Larsen B Ice Shelf in 2002. Then the Wilkins Ice Shelf in 2008.
The Intergovernmental Panel on Climate Change (IPCC) projects that global warming will cause worldwide sea levels to rise between 1 foot and 3 feet, on average, by 2100. That’s partly because ocean water expands as it warms. But it’s partly because more ice from Antarctica, Greenland, and other glaciers is melting and flowing into the oceans, pushing up sea levels. Over the longer term, however, Antarctica has the capability of raising sea levels much, much higher. West Antarctica’s ice sheet contains enough ice to raise sea levels worldwide by 10 to 14 feet, on average. Then there’s the even more massive East Antarctica ice sheet, which contains enough ice to raise global sea levels by another 190 feet or so. Thankfully, this sheet appears far more stable, and it would take many, many centuries for all that ice to melt. Yet if even a fraction of that ice slid into the sea, it would alter coastlines and cities dramatically for generations to come.