The world’s largest ice sheet, in Antarctica, is losing mass and this has implications for sea-level rise. Ice is slipping into the sea from the continent’s edge faster than snowfall is accumulating in the high-altitude interior. This imbalance means that Antarctic ice loss is contributing to a rising sea level. A new satellite map reveals the new grounding line of the East Antarctica’s coastline around Law Promontory near Stefansson Bay. The grounding line is the point where the ice sheet separates from land and begins to float on the ocean and it is significantly further inland than previously estimated. "This new map provides us the best possible estimate of where the grounding line actually is and the thickness of the ice there. This is vital for calculating the rate of ice flow from the grounded ice into he sea," said Neal Young, ACE Glaciologist. The new map is the result of an international effort called the Antarctic Surface Accumulation and Ice Discharge (ASAID) project, led by Robert Bindschadler of NASA’s Goddard Space Flight Center. Researchers used data and images from multiple sources—including images from Landsat 7 and the LIMA mosaic, precise elevation data from ICESat, as well as grounding line estimates from earlier studies—to create the most detailed map yet produced. "This project has been a major achievement to come from the International Polar Year. This project included young scientists, it was an international effort, and it produced freely available data—all from satellites," said Dr Bindschadler. The dramatic improvement provided by the new map is most apparent around the rocky outcrops off the coast; smatterings of ice-encased islands are a common occurrence around Antarctica. The earlier map included the rocky outcrops and sometimes icebergs as part of the ice sheet perimeter, but elevation data and interpretation based on higher-resolution, and hence more detailed imagery, enabled researchers to identify the ice perimeter more accurately. To complete its map, the team connected 3.5 million geographic points around Antarctica. The team identified a new perimeter for Antarctica’s ice as being roughly 53,610 kilometers (33,312 miles). Ted Scambos from the National Snow and Ice Data Center said, "ASAID doesn’t just show the location of the ice edge, it provides the elevation all along that line. That’s a key step in measuring mass balance because it tells you the ice thickness near the grounding line."

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