Antarc­tic thaw quick­ens, tril­lions of tonnes of ice raise sea lev­els

The Borneo Post - - WORLD -

OSLO: An ac­cel­er­at­ing thaw of Antarc­tica has pushed up world sea lev­els by al­most a cen­time­tre since the early 1990s in a risk for coasts from Pa­cific is­lands to Florida, an in­ter­na­tional team of sci­en­tists said yes­ter­day.

Antarc­tica has enough ice to raise seas by 58 me­tres if it ever all melted, dwarf­ing frozen stores in places from Green­land to the Hi­malayas and mak­ing its fu­ture the big­gest un­cer­tainty in un­der­stand­ing global warm­ing and ocean lev­els.

The frozen con­ti­nent lost al­most three tril­lion tonnes of ice be­tween 1992 and 2017, the 84 sci­en­tists said in what they called the most com­plete over­view of Antarc­tic ice to date.

The thaw, tracked by satel­lite data and other mea­sure­ments, con­trib­uted 0.76 cm to sea level rise since 1992, they wrote in the jour­nal Na­ture.

And the ice losses quick­ened to 219 bil­lion tonnes a year since 2012, from 76 bil­lion pre­vi­ously.

“The sharp in­crease ... is a big sur­prise,” pro­fes­sor An­drew Shep­herd of the Univer­sity of Leeds and a leader of the re­port, told Reuters.

The sharp in­crease ... is a big sur­prise. Pro­fes­sor An­drew Shep­herd, Univer­sity of Leeds

Most ice was be­ing lost from West Antarc­tica and the Antarc­tic Penin­sula, where warmer ocean wa­ter is melt­ing float­ing ice shelves at the end of glaciers, al­low­ing ice pent up on land to slide faster to­wards the sea, the study said.

A sin­gle mil­lime­tre of global sea level rise is equivalent to 360 bil­lion tonnes of melted ice, or an imag­i­nary gi­gan­tic ice cube with sides about seven kilo­me­tres long.

Over­all, world sea lev­els have risen about 20 cm in the past cen­tury, driven mainly by a nat­u­ral ex­pan­sion of wa­ter al­ready in the oceans as it warms along with a thaw of glaciers form the An­des to the Alps.

And a ma­jor UN as­sess­ment in 2014 said seas could rise this cen­tury by be­tween about 30 cm and al­most a me­tre.

Shep­herd said Antarc­tica alone is now on track to raise world sea lev­els by about 15 cm by 2100, above most past es­ti­mates.

Such a rise alone sounds lit­tle but would make coastal floods dur­ing storms at high tides more dam­ag­ing, he said. Sea level rise is a threat to cities from New York to Shang­hai as well as low-ly­ing na­tions from the Pa­cific Ocean to the Nether­lands.

“We’re watch­ing these re­ports closely,” said Michiel van den Broeke, pro­fes­sor of Po­lar Me­te­o­rol­ogy at Utrecht Univer­sity in the Nether­lands, say­ing they were the guide for de­fend­ing the Dutch coast.

Un­der the 2015 Paris cli­mate agree­ment, al­most 200 gov­ern­ments set a goal of phas­ing out fos­sil fu­els this cen­tury to limit warm­ing. US Pres­i­dent Don­ald Trump plans to pull out of the pact and to fo­cus in­stead on US jobs and coal.

Chris Rap­ley, a pro­fes­sor of cli­mate science at Univer­sity Col­lege London who was not in­volved in the study, wrote in a com­ment that he had sug­gested in 2005 that a “slum­ber­ing gi­ant (of ice in Antarc­tica) seemed to be awak­en­ing. This pa­per sug­gests it is stretch­ing its limbs.” — Reuters

File photo of an ice­berg floats in And­vord Bay, Antarc­tica. — Reuters photo

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