Vast store of wa­ter lies un­der Green­land

China Daily (Hong Kong) - - WORLD - By RICHARD ING­HAM in Paris Agence France-Presse

A vast store of wa­ter equiv­a­lent in area to Ire­land lies be­neath Green­land’s ice sheet, and may pro­vide an­swers to one of the big­gest rid­dles about cli­mate change, sci­en­tists said on Sun­day.

In 2011, US sci­en­tists crossed the south­ern Green­land ice sheet on an ex­pe­di­tion to drill ice cores, a bench­mark of an­nual snow­fall.

They were stunned when they drilled into a layer of com­pressed snow called firn, for in­stead of pierc­ing an icy sponge at a depth of 10 me­ters as ex­pected, they en­coun­tered wa­ter and ice gran­ules in­stead.

They car­ried out another drilling a few kilo­me­ters away, with the same re­sult when they reached the firn layer at 25 me­ters.

Seek­ing an an­swer to the wa­ter mys­tery, a NASA plane with ter­rain-map­ping radar was brought in to fly over the zone, as well as ground-pen­e­trat­ing radar towed by a snow­mo­bile.

Radar re­turned bright re­flec­tions point­ing to the pres­ence of a vast reser­voir of wa­ter be­neath the ice.

Ex­tend­ing down Green­land’s south­east­ern flank, the hid­den wa­ter cov­ers 70,000 square kilo­me­ters and is found at depths be­neath the ice that range from five to 50 me­ters.

Sur­pris­ing fact

The store is be­lieved to hold melted snow from the pre­vi­ous sum­mer, ac­cord­ing to a pa­per pub­lished in the jour­nal Na­ture Geo­science.

It works sim­i­larly to an aquifer be­low the ground, which is a spongy rock that holds wa­ter in its air spa­ces.

In this case, the air spa­ces in the firn are oc­cu­pied by wa­ter, re­sult­ing in some­thing akin to the crushed-ice soft drink called a snow cone.

“The sur­pris­ing fact is the juice in this snow cone never freezes, even in the dark Green­land win­ter,” said Rick Forster, a ge­og­ra­phy pro­fes­sor at the Univer­sity of Utah, who led the mis­sion.

“Large amounts of snow fall on the sur­face later in the sum­mer and quickly in­su­late the wa­ter from the sub-freez­ing air tem­per­a­tures above, al­low­ing the wa­ter to per­sist all year long.”

The se­cret store ap­pears to have been around for some time and was not ini­ti­ated by man­made global warm­ing, the sci­en­tists be­lieve.

They say it could pro­vide in­sights into the fate of the ice sheet, a key ques­tion in cli­mate sci­ence.

A mighty slab of ice av­er­ag­ing 1,500 me­ters in thick­ness, Green­land is ex­pe­ri­enc­ing un­prece­dented melt as global warm­ing ac­cel­er­ates.

In 2012, the ice sheet lost a record 250 cu­bic kilo­me­ters in vol­ume, mak­ing it the big­gest sin­gle con­trib­u­tor to the rise in world sea lev­els, Forster said.

If the ice sheet melts com­pletely, it will in­crease sea lev­els by about seven me­ters.

This is a dooms­day sce­nario that most sci­en­tists dis­count, but even the loss of a large frac­tion would still drown vul­ner­a­ble coastal cities.

The dis­cov­ery of a year-round sub- glacial reser­voir sweeps away com­puter sim­u­la­tions that have tried to cal­cu­late this runoff.

The sim­u­la­tions usu­ally have wa­ter flow­ing into rivers, lakes or sub-glacial streams that even­tu­ally run into the sea, or else run­ning into the ice sheet through crevasses and be­com­ing frozen.

The next step is to deter­mine whether the reser­voir helps or hin­ders the sur­vival of Green­land’s ice sheet.

“It might con­serve the melt­wa­ter flow and thus help slow down the ef­fects of cli­mate change,” Forster said.

“But it may also have the op­po­site ef­fect, pro­vid­ing lu­bri­ca­tion to mov­ing glaciers and ex­ac­er­bat­ing ice ve­loc­ity and (ice­berg) calv­ing, in­creas­ing the mass of ice loss to the global ocean.”

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