TEMPO.CO, Greenland - It's big. It's cold. And it's melting into the world's ocean.
It's Zachariae Isstrom, the latest in a string of Greenland glaciers to undergo rapid change in our warming world. A new NASA-funded study published today in the journal Science finds that Zachariae Isstrom broke loose from a glaciologically stable position in 2012 and entered a phase of accelerated retreat. The consequences will be felt for decades to come.
The reason? Zachariae Isstrom is big. It drains ice from an area of 35,440 square miles (91,780 square kilometers). That's about 5 percent of the Greenland Ice Sheet. All by itself, it holds enough water to raise global sea level by more than 18 inches (46 centimeters) if it were to melt completely. And now it's on a crash diet, losing 5 billion tons of mass every year. All that ice is crumbling into the North Atlantic Ocean.
"North Greenland glaciers are changing rapidly," said lead author Jeremie Mouginot, an assistant researcher in the Department of Earth System Science at the University of California, Irvine. "The shape and dynamics of Zachariae Isstrom have changed dramatically over the last few years. The glacier is now breaking up and calving high volumes of icebergs into the ocean, which will result in rising sea levels for decades to come."
Mouginot and his colleagues from NASA's Jet Propulsion Laboratory, Pasadena, California; and the University of Kansas, Lawrence, set out to study the changes taking place at Zachariae Isstrom.
The team used data from aerial surveys conducted by NASA's Operation IceBridge and satellite-based observations acquired by multiple international space agencies (NASA, ESA, CSA, DLR, JAXA and ASI) coordinated by the Polar Space Task Group. The NASA satellite data used are from the joint NASA/USGS Landsat program. The various tools used -- including a highly sensitive radar sounder, gravimeter and laser profiling systems, coupled with radar and optical images from space -- monitor and record changes in the shape, size and position of glacial ice over long time periods, providing precise data on the state of Earth's polar regions.
The scientists determined the bottom of Zachariae Isstrom is being rapidly eroded by warmer ocean water mixed with growing amounts of meltwater from the ice sheet surface. "Ocean warming has likely played a major role in triggering [the glacier's] retreat," Mouginot said, "but we need more oceanographic observations in this critical sector of Greenland to determine its future."
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