Red Orbit
Antarctica may not be the world’s largest landmass — it’s the fifth-largest continent — but resting on top of that land is the world’s largest ice sheet. That ice holds more than 60 percent of Earth’s fresh water and carries the potential to significantly raise sea level. The continent is losing ice to the sea, and scientists want to know how much.
Antarctica’s ice generally flows from the middle of the continent toward the edge, dipping toward the sea before lifting back up and floating. The point where ice separates from land is called the “grounding line.” For scientists, an accurate map of the grounding line is a first step toward a complete calculation of how much ice the continent is losing.
Such a map is a primary objective of the Antarctic Surface Accumulation and Ice Discharge (ASAID) project. Researchers from NASA’s Goddard Space Flight Center in Greenbelt, Md., led a team that used high-resolution satellite images, along with newly developed computer software, to trace the most accurate Antarctic grounding line ever compiled.
“This project has been a major achievement to come from the International Polar Year,” said Robert Bindschadler, a cryosphere scientist based at Goddard who presented his team’s work in June at the International Polar Year Oslo Science Conference. “This project included young scientists, it was an international effort, and it produced freely available data — all from satellites.”
Much public attention has been focused on the Arctic, where ice loss is accelerating. Antarctica, however, is also steadily losing ice. NASA satellites have shown ice losses around the entire continent, with pronounced changes in the northern region around the Antarctic Peninsula. The most significant changes are likely to occur at the intersection of the ocean and the ice sheets.
At what rate is Antarctica’s ice is lost to the ocean? It’s a tricky question because of Antarctica’s immense scale. Previously, researchers calculated the speed of outflow from 33 of Antarctica’s biggest outlet glaciers, but that accounts for just half of what is lost, as outlet glaciers makes up only 5 percent of the coastline.
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