Frozen gi­ant breaks loose from ice shelf Tril­lion-ton ice­berg sparks de­bate over cli­mate change fac­tor

China Daily (Hong Kong) - - WORLD -

MEL­BOURNE, Aus­tralia — One of the big­gest ice­bergs ever recorded, a tril­lion-ton be­he­moth more than five times the size of Hong Kong, has bro­ken off Antarc­tica, trig­ger­ing dis­agree­ment among sci­en­tists over whether global warm­ing is to blame.

The event, cap­tured by satel­lite, hap­pened some­time in the past few days when the gi­ant chunk snapped off an ice shelf.

While such “calv­ing” of ice­bergs is not un­usual, this is an espe­cially big one, cov­er­ing roughly 6,000 square kilo­me­ters.

Its vol­ume is twice that of Lake Erie, the fourth-largest of the five Great Lakes in North Amer­ica, and the 13thlargest glob­ally if mea­sured in terms of sur­face area.

The ice­berg, known as A68, broke loose from the Larsen C ice shelf, which sci­en­tists had been mon­i­tor­ing for months as they watched a crack grow more than 200 km long.

Sci­en­tists say global warm­ing has caused a thin­ning of such shelves, but they dif­fer on whether the lat­est event can be blamed on cli­mate change.

The ice­berg is con­sid­ered un­likely to pose any threat to ship­ping. And since the ice was al­ready float­ing, the breakup won’t raise sea lev­els in the short term, the project said in a state­ment.

But it re­moved more than 10 per­cent of the ice shelf, and if that even­tu­ally has­tens the flow of glaciers be­hind it into the wa­ter, there could be a “very mod­est” rise in sea level, the project said.

Watch­ing closely

Two other Antarc­tic ice shelves, far­ther north on the Antarc­tic Penin­sula, col­lapsed in 1995 and 2002. That sped up the slide of glaciers, which con­trib­uted to sea-level rise, David Vaughan, di­rec­tor of science at the Bri­tish Antarc­tic Sur­vey, said in a state­ment.

“Our glaciol­o­gists will now be watch­ing closely to see whether the re­main­ing Larsen C ice shelf be­comes less sta­ble than be­fore the ice­berg broke free,” he said.

Swansea Univer­sity glaciol­o­gist Martin O’Leary, a mem­ber of the MIDAS project, called it “a nat­u­ral event, and we’re not aware of any link to hu­man-in­duced cli­mate change.”

How­ever, Ian Sim­monds, a pro­fes­sor at the School of Earth Sciences at the Univer­sity of Mel­bourne, said man­made global warm­ing had ac­cel­er­ated the process.

“The calv­ing of this huge ice­berg from the Larsen C ice shelf is deeply trou­bling. This fol­lows the col­lapse of part of the Larsen B ice shelf in Feb­ru­ary 2002,” Sim­monds said.

“The causes of these breakups are sim­i­lar. Tem­per­a­tures have risen dra­mat­i­cally in the re­gion over re­cent decades. This has meant that sum­mer tem­per­a­tures now fre­quently get above freez­ing, and the as­so­ci­ated sur­face melt­ing sig­nif­i­cantly weak­ens the ice shelves.”

A spokes­woman for the Bri­tish Antarc­tic sur­vey said there’s not enough in­for­ma­tion to say whether the calv­ing is an ef­fect of cli­mate change, though there’s good ev­i­dence global warm­ing has caused thin­ning of the ice shelf.

As for any dan­ger to nav­i­ga­tion, sci­en­tists said the ice­berg will prob­a­bly break up and its pieces will cir­cle Antarc­tica for years or decades rather than drift­ing north­ward into ship­ping lanes.

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