Sci­en­tists sound alarm as Antarc­tica melt ac­cel­er­ates

Scholar: Con­ti­nent dis­ap­pear­ing faster than ex­pected

Baltimore Sun - - NATION & WORLD - By Seth Borenstein

WASH­ING­TON — The melt­ing of Antarc­tica is ac­cel­er­at­ing at an alarm­ing rate, with about 3 tril­lion tons of ice dis­ap­pear­ing since 1992, an in­ter­na­tional team of ice ex­perts said in a new study.

In the last quar­ter cen­tury, the south­ern-most con­ti­nent’s ice sheet — a key indi­ca­tor of cli­mate change — melted into enough wa­ter to cover Texas to a depth of nearly 13 feet, sci­en­tists cal­cu­lated. All that wa­ter made global oceans rise about three­tenths of an inch.

From 1992 to 2011, Antarc­tica lost nearly 84 bil­lion tons of ice a year. From 2012 to 2017, the melt rate in­creased to more than 241 bil­lion tons a year, ac­cord­ing to the study Wed­nes­day in the jour­nal Na­ture.

“I think we should be wor­ried. That doesn’t mean we should be des­per­ate,” said Univer­sity of Cal­i­for­nia, Irvine’s Is­abella Velicogna, one of 88 coau­thors. “Things are hap­pen­ing. They are hap­pen­ing faster than we ex­pected.”

Part of West Antarc­tica, where most of the melt­ing oc­curred, “is in a state of col­lapse,” said co-au­thor Ian Joughin of the Univer­sity of Wash­ing­ton.

The study is the sec­ond of as­sess­ments planned every sev­eral years by a team of sci­en­tists work­ing with NASA and the Euro­pean Space Agency. Their mis­sion is to pro­duce the most com­pre­hen­sive look at what’s hap­pen­ing to the world’s vul­ner­a­ble ice sheets in Antarc­tica and Green­land.

Out­side ex­perts praised the work as au­thor­i­ta­tive.

Un­like sin­gle-mea­sure- An ice­berg is seen near an Antarc­tic re­search sta­tion. Antarc­tica alone could add about half a foot to sea level rise by the end of the cen­tury, one re­searcher said. ment stud­ies, this team looks at ice loss in 24 dif­fer­ent ways us­ing 10 to 15 satel­lites, as well as ground and air mea­sure­ments and com­puter sim­u­la­tions, said lead au­thor An­drew Shep­herd of the Univer­sity of Leeds in Eng­land.

It’s pos­si­ble that Antarc­tica alone can add about half a foot to sea level rise by the end of the cen­tury, Shep­herd said. Seas also rise from melt­ing land glaciers else­where, Green­land’s dwin­dling ice sheet and the fact that warmer wa­ter ex­pands.

“Un­der nat­u­ral con­di­tions we don’t ex­pect the ice sheet to lose ice at all,” Shep­herd said. “There are no other plau­si­ble sig­nals to be driv­ing this other than cli­mate change.”

Shep­herd cau­tioned that this is not a for­mal study that de­ter­mines hu­man fin­ger­prints on cli­mate events.

Forces “that are driv­ing these changes are not go­ing to get any bet­ter in a warm­ing cli­mate,” said Univer­sity of Colorado ice sci­en­tist Waleed Ab­dalati, a for­mer NASA chief sci­en­tist who wasn’t part of the study team.

In Antarc­tica, it’s mostly warmer wa­ter caus­ing the melt. The wa­ter nib­bles at the float­ing edges of ice sheets from be­low. Warm­ing of the south­ern ocean is con­nected to shift­ing winds, which are con­nected to global warm­ing from the burn­ing of coal, oil and nat­u­ral gas, Shep­herd said.

More than 70 per­cent of the re­cent melt is in West Antarc­tica.

The lat­est fig­ures show East Antarc­tica is los­ing rel­a­tively lit­tle ice a year — about 31 tons — since 2012. It was gain­ing ice be­fore 2012.

So far sci­en­tists are not com­fort­able say­ing the trend in East Antarc­tica will con­tinue. It is likely nat­u­ral vari­abil­ity, not cli­mate change, and East Antarc­tica is prob­a­bly go­ing to be sta­ble for a cou­ple decades, said study co-au­thor Joughin.

An­other study in Na­ture on Wed­nes­day found that East Antarc­tic ice sheet didn’t re­treat sig­nif­i­cantly 2 mil­lion to 5 mil­lion years ago when heat-trap­ping car­bon diox­ide lev­els were sim­i­lar to what they are now.

Twila Moon, a re­search sci­en­tist at the Na­tional Snow and Ice Data Cen­ter who wasn’t part of the stud­ies, said “ice-speak­ing, the sit­u­a­tion is dire.”


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