A New Theory Explains What's Driving Antarctica's Fastest Melting Glacier
Researchers previously pinpointed continental winds as the force pushing warm ocean waters underneath West Antarctica's Pine Island Glacier, but now they say local weather patterns are to blame.
New analysis indicates that local weather conditions, not continental winds as previously thought, could be driving the rapid retreat of the Pine Island Glacier, the fastest melting glacier in Antarctica.
Scientists from the University of East Anglia used records between 2009 and 2014 to determine how local atmospheric conditions are directly affecting the ocean conditions that are rapidly melting the Pine Island Ice Shelf, part of the West Antarctic Ice Sheet that sits at the base of the South Pacific Ocean.
While previous studies suggested that winds coming off of the continental shelf - some 250 miles to the north - were pushing warm waters beneath the western Antarctic, warming the Pine Island Glacier and others from beneath, scientists from the University of East Anglia saw little evidence for that.
"People thought that it was the wind, at the edge of the continental shelf, that was determining how much water was pushed onto the shelf, warming the glacier from beneath," said Ben Webber, an oceanographer at the University of East Anglia and lead researcher on the study.
Instead, by analyzing a five-year set of records, Webber and his team found that local weather, rather than continental winds, were driving the ocean temperatures at a crucial depth between 1,150 to 2,300 feet, the range in which the base of the glacier comes into contact with ocean water.
"Most of the ocean data around Antarctica are snapshots of conditions - and many areas are only visited once every one or two years, if that," Povl Abrahamsen, co-author of the study and an oceanographer at British Antarctic Survey, said in a statement. "A five-year time series," he said, "lets us see what is happening between these snapshots, giving us insights into the processes driving the melting of Pine Island Glacier."
The report, published in Nature Communications, comes in the midst of news that another iceberg has broken from the Pine Island Glacier. On Thursday, NASA satellites documented a 1-mile-long iceberg calving from the glacier and moving into the adjacent Amundsen Sea. Scientists have called the incident an "aftershock," resulting from a much bigger separation event in 2015, when an iceberg measuring 278 square miles - the size of Chicago - broke from the Pine Island Glacier.
The glacier, one of the largest in the West Antarctic Ice Sheet, is estimated to account for 20 percent of total ice flow into the ocean - some 19 cubic miles of ice per year, according to NASA. In recent years, as its flow into the ocean has accelerated, the glacier has become symbolic of a fragile, retreating Antarctic glacial system.
Researchers have described the Pine Island Glacier as the "plug" that holds back the expansive West Antarctic Ice Sheet, the melting of which contributes to sea-level rise. According to Webber and his team, this long-ranging data may offer important clues as to how to best measure the retreat of glaciers that could lead to major sea level rise.
While past melting has been offset by accumulation of hail and ice, in recent decades, Webber said, "This system has gone out of balance."
Earlier this week, Ian Howat, a glaciologist at Ohio State University, told NASA that the thinning of Pine Island Glacier "fits into the larger picture of basal crevasses in the center of the ice shelf being eroded by warm ocean water, causing the ice shelf to break from the inside out."
Without major measures taken to halt the effects of climate change in the Antarctic, there is little to be done to stop the retreat of glaciers like Pine Island. But Webber is hopeful that their data could help to sound an early alarm as such calving events continue in coming years.
"If we understand what might be cause these glaciers to melt, we can better pinpoint the measurements we need to take in order to warn of potential collapse and the impact that would have on sea level rise," said Webber.