Times Colonist - - World -

WASHINGTON — The melt­ing of Antarc­tica is ac­cel­er­at­ing at an alarm­ing rate, with 2.7 tril­lion tonnes 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 four me­tres, sci­en­tists cal­cu­lated. That made global oceans rise about 7.6 mil­lime­tres.

From 1992 to 2011, Antarc­tica lost nearly 76 bil­lion tonnes of ice a year. From 2012 to 2017, the melt rate in­creased to more than 219 bil­lion tonnes 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 co-au­thors. “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-mea­sure­ment 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 16 cen­time­tres 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.


An un­usual ice­berg floats near the Rothera Re­search Sta­tion on the Antarc­tic Penin­sula in Jan­uary.

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