Antarctica’s ocean-front glaciers are retreating, according to a new satellite survey that raises additional concerns about the massive continent’s potential contribution to rising sea levels.
Antarctica, which contains enough ice to raise the oceans by about 200 feet (60 meters), is a continent of ice that flows outward to the ocean at numerous large glaciers.
These mostly submerged glaciers rest deep on the seafloor at a point called the “grounding line”, where ocean, ice and bedrock meet.
But at 10.7 percent of these glaciers, the ice masses are moving at a significant speed back toward the center of the continent as they melt from below, often because of the incursion of warm ocean water, which causes the grounding line to retreat.
Only about 1.9 percent of glaciers were growing at a significant speed, suggesting a net retreat.
And the more glaciers are retreating, the more one worries about sea-level rise. Retreating grounding lines can expose more ice to the ocean, allowing it to flow outward more rapidly.
The research used satellite techniques to infer changes to glacier grounding lines based on changes in the height of the glacier’s surface.
Scanning one-third of Antarctica’s marine-based glaciers along a roughly 10,000-mile (16,000 km) stretch of coastline, the work presents a more comprehensive look than other studies of Antarctic glaciers, which have tended to focus on grounding lines in just one key region.
“We were able to quantify more or less all around Antarctica,” said Hannes Konrad, the lead author of the research. Konrad works at the University of Leeds in Britain, along with a number of co-authors of the study. Other authors worked at University College London.
The research found that from 2010 through 2016, about 80 square miles (200 square km) per year of ice is being lifted off of the seafloor and going afloat as grounding lines retreat. That’s about four times the size of Manhattan every year.