Why a melting Greenland is likely to trigger world’s deadliest quake

Should all of the ice sheet ever thaw, the meltwater could raise sea level 21 feet. By 2005, Greenland was beginning to lose more ice volume than anyone had anticipated — an annual loss of up to 52 cubic miles a year — according to more recent satellite gravity measurements. The volume of freshwater ice dumped into the Atlantic Ocean has almost tripled in a decade.

HOW

The glaciers of Greenland are melting twice as fast as they were five years ago, even as the ice sheets of Antarctica — the world’s largest reservoir of fresh water — also are shrinking, researchers at NASA’s Jet Propulsion Laboratory and the University of Kansas reported. The area of seasonal melting was broader last year than in 27 years of record-keeping, University of Colorado climate scientists reported. In early May, temperatures on the ice cap were almost 20 degrees above normal, hovering just below freezing. Last year, there was even a period of melting in December.

WHY

Contrary to appearances, the monolith of ice is constantly on the move — on average, at about 1 foot every day. Ice move faster when the surface ice starts to melt. By 1999, the ice stream had almost tripled its speed to about 3 feet a day as the warm water made its way through thousands of feet of ice to the bedrock — in weeks, not decades or centuries. So much water streamed beneath the ice that in high summer the ice sheet can briefly bulged 2 feet higher, like the crest of a subterranean wave.

University of Texas physicist Ginny Catania pulled an ice-penetrating radar, seeking evidence of any melt holes or drainage crevices that could so quickly channel the hot water of global warming deep into the ice. To her surprise, she detected a maze of tunnels, natural pipes and cracks beneath the unblemished surface.

The 6th WHAT NEXT

Since 2002, Greenland’s three largest outlet glaciers have started moving faster, satellite data show. In all, 12 major outlet glaciers drain the ice sheet, setting the pace of its release to the ocean. If they all slide too quickly, perhaps in a few decades, they could collapse suddenly and release the entire ice sheet into the ocean.

The accelerating ice flow will cause a dramatic increase in seismic activity, as the three immense streams of ice shake the earth in their wake.

Already there are ominous signs. Last year alone, the Harvard and Columbia researchers detected as many ice quakes — up to magnitude 5.0 — as the total recorded from 1993 through 1996, with five times as many in the summer as in the winter months.