Pine Island Glacier has shed another block of ice into Antarctic waters. While the loss was tiny compared to the icebergs that broke off in 2014 and 2015, the event is further evidence of the ice shelf’s fragility.
Pine Island is one of the main glaciers responsible for moving ice from the interior of the West Antarctic Ice Sheet to the ocean. It already delivers plenty of ice to Pine Island Bay about 79 cubic kilometers of ice per year.
But scientists watch this glacier closely because the evidence has been pointing to even faster loss of ice in the future. Such a retreat would lessen the shelf’s buttressing effect, allowing more inland ice to flow out to the ocean, where it ultimately melts and contributes to sea level rise.
The Operational Land Imager (OLI) on Landsat 8 captured the image pictured here of Pine Island Glacier’s floating edge on 26 January, after the recent break. About a kilometer or two of ice appears to have calved (broken off) from the shelf’s front.
According to Ian Howat, a glaciologist at Ohio State University, the event was about 10 times smaller than in July 2015, when a 30-kilometer-long (20-mile) rift developed below the ice surface, then broke through and calved an iceberg spanning 583 square kilometer.
“I think this event is the calving equivalent of an ‘aftershock’ following the much bigger event,” Howat says. “Apparently, there are weaknesses in the ice shelf – just inland of the rift that caused the 2015 calving – that are resulting in these smaller breaks.”
Although not visible in these images, more small rifts persist on Pine Island about 10 kilometers from the ice front.
“Such ‘rapid fire’ calving does appear to be unusual for this glacier,” Howat says. But the phenomenon “fits into the larger picture of basal crevasses in the centre of the ice shelf being eroded by warm ocean water, causing the ice shelf to break from the inside out.”
Image Credit: NASA Earth Observatory image by Jesse Allen, using Landsat data from the US Geological Survey and MODIS data from the Level 1 and Atmospheres Active Distribution System (LAADS)