One of the world’s most rapidly flowing glaciers may have just set another record, and it’s not one not that bodes well for low-lying coastal cities and nations around the world, which are vulnerable to sea level rise.
During the past month, a NASA satellite as well as European satellites captured images showing a sudden loss of ice, also known as a calving event (or in this case, possibly multiple events) from Greenland’s Jakobshavn Isbrae Glacier between July 31 and August 19, 2015.
Images posted on the Arctic sea ice blog, which closely tracks developments in the Arctic, narrowed the timeline of the ice loss to between August 14 and 16. This is backed up by observations from satellites operated by the European Space Agency, or ESA.
NASA satellite images on July 31, 2015 (first) and then on August 16, 2015 (second), showing the movement of the calving front further inland, or to the right.
It’s unclear if this sudden ice loss set a record, according to NASA.
“Some observers have speculated that the area of ice lost could be the largest on record. However, these estimates are preliminary, and satellite images from before and after an event cannot show whether the ice was lost all at once, or in a series of smaller events,” NASA stated on its Earth Observatory website.
Nevertheless, the event was significant because it once again signaled the rapidly changing ice conditions in Greenland as air and ocean temperatures increase.
According to the ESA, the calving front now appears to be located at its most easterly location since monitoring began in the mid-1880s. Data from two ESA satellites, known as Sentinel 1A and 2A, show that the glacier lost a total area of 12.5 square kilometers, or about 4.8 square miles, in this calving event.
“Assuming the ice is about 1400 meters deep, this equates a volume of 17.5 cubic km — which could cover the whole of Manhattan Island by a layer of ice about 300 m thick,” the agency stated on its website.
In other words, the ESA data shows that the ice that broke off in the latest calving event would be sufficient to cover Manhattan in nearly 1,000 feet of ice.
Faster ice loss
“The calving events of Jakobshavn are becoming more spectacular with time, and I am in awe with the calving speed and retreat rate of this glacier,” said Eric Rignot, a glaciologist at NASA’s Jet Propulsion Laboratory, in a statement.
Studies have shown that Jakobshavn’s summer flow speeds have sped up dramatically during the past few decades, and this one glacier was responsible for raising global average sea level by about 1 millimeter, or .04 inches, between 2000 and 2010, a figure that is likely to increase as global warming continues.
Jakobshavn retreated more than 25 miles between 1850 and 2010, and since 2010, the retreat has sped up dramatically.
In fact, a 2014 study published in the open access journal Cryosphere found that the glacier was moving at average speeds of about half-a-mile per year, or more than 150 feet per day, during the summers of 2012 and 2013.
“We are now seeing summer speeds more than four times what they were in the 1990s, on a glacier which at that time was believed to be one of the fastest, if not the fastest, glacier in Greenland,” said study author Ian Joughin, a glaciologist at the University of Washington, in apress release when that study was published.
Jakobshavn is not just any old glacier. It’s important because it helps drain a large portion of the Greenland Ice Sheet. As it moves faster, it transports more ice at a faster rate into the sea, adding to sea level rise.
“This glacier alone could contribute more to sea level rise than any other single feature in the Northern Hemisphere,”
“This glacier alone could contribute more to sea level rise than any other single feature in the Northern Hemisphere,” NASA stated on its website.
According to the ESA, this glacier drains 6.5% of the Greenland ice sheet, producing around 10% its icebergs. The agency said in a statement that this totals about 35 billion tonnes of ice calved off each year.
Given its rapid movement, Jakobshavn has been the scene of several famous large calving events, including one in July 2010, when the glacier shed a 2.7 square-mile chunk of ice in the span of 24 hours, pushing the calving front one mile further inland.
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