Thick, impenetrable ice slabs are expanding rapidly on the interior of Greenland's ice sheet, where the ice is normally porous and able to reabsorb meltwater. These slabs are instead sending meltwater spilling into the ocean, according to a new CIRES-led assessment, threatening to increase the country's contribution to sea level rise by as much as 2.9 inches by 2100.
Although runoff from ice slabs has added less than a millimeter to global sea levels so far, this contribution will grow substantially as ice slabs continue to expand in a warming climate, said Mike MacFerrin, a CIRES and University of Colorado Boulder researcher who led the new study, published today in Nature. “Even under moderate climate projections, ice slabs could double the size of the runoff zone by 2100,” MacFerrin said. “Under higher emissions scenarios, the runoff zone nearly triples in size.”
In 2000, Greenland’s runoff zone—the region of the ice sheet where runoff contributes to sea level rise—was roughly the size of New Mexico. Between 2001 and 2013, ice slabs expanded the runoff zone by about 65,000 km2—that’s an average pace of two American football fields a minute. By 2100, as Earth’s temperatures continue to climb and ice slabs continue to grow, the runoff zone could expand by the size of Colorado under a moderate emissions scenario, the team found. That would raise seas by an extra quarter inch to just over an inch (7-33 mm).
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