Heat held in Arc­tic Ocean dou­bled

Heat could slow growth of win­ter ice, says Yale Univer­sity re­searcher

The Peterborough Examiner - - Canada & World - BOB WE­BER

Newly-pub­lished re­search sug­gests the amount of heat stored in a vast sec­tion of the Arc­tic Ocean has dou­bled over the last 30 years, adding an­other blow to sea ice that helps reg­u­late the planet’s cli­mate.

“The most likely out­come for this heat is that it will slow the growth of win­ter sea ice, which fur­ther com­pro­mises the Arc­tic sea ice pack,” said Mary-Louise Tim­mer­mans of Yale Univer­sity.

Tim­mer­mans is one of the au­thors of a pa­per pub­lished Wed­nes­day that ex­am­ined 30 years worth of mea­sure­ments at dif­fer­ent depths in the Canada Basin, a large sec­tion of the Arc­tic Ocean west of Canada’s High Arc­tic Is­lands.

That ocean is com­posed of lay­ers di­vided by both salin­ity and tem­per­a­ture. One of those lay­ers, be­gin­ning at about 50 me­tres of depth, is both more saline and warmer than the sur­face wa­ters.

That layer has prob­a­bly al­ways been there and comes from wa­ters hun­dreds of kilo­me­tres to the south in the Chukchi Sea, said Tim­mer­mans.

Those wa­ters move north through a nat­u­ral cur­rent called the Beaufort Gyre. When they get far enough north, their higher salin­ity makes them heav­ier than the water around them and they sink below the sur­face.

But cli­mate change means the Chukchi Sea has been los­ing sea ice in re­cent decades. That has al­lowed the sun to warm it up.

“We’re see­ing more and more open water as the sea ice re­treats in the sum­mer­time,” Tim­mer­mans said. “The sun is warm­ing up the ocean di­rectly, be­cause it’s no longer cov­ered by sea ice.”

The pa­per cal­cu­lates that sea is now ab­sorb­ing five times more so­lar en­ergy than it did pre­vi­ously.

That sun-warmed water has cre­ated what Tim­mer­mans calls “archived” heat in the Canada Basin.

“That layer of water is both in­creas­ing in tem­per­a­ture and also in­creas­ing in thick­ness. Over­all, it’s in­creas­ing heat con­tent.”

Some of that heat trick­les up to the sur­face of the Canada Basin, one of the places that still has a sum­mer ice cover. Tim­mer­mans said that heat will slow and weaken the for­ma­tion of win­ter ice.

Although that water has only been warmed to a max­i­mum tem­per­a­ture of about 0 C, the pa­per cal­cu­lates there is cur­rently enough new heat stored be­neath the ocean sur­face to thin the ice cover of the en­tire basin by nearly a me­tre.

Re­search notes that the amount of such “archived” heat will con­tinue to grow as the Chukchi loses more ice.

What’s hap­pen­ing in the Canada Basin is an ex­am­ple of how los­ing sea ice in one area can con­trib­ute to fur­ther sea ice losses in ar­eas hun­dreds of kilo­me­tres away, the pa­per says.

The ul­ti­mate con­se­quences are un­known, Tim­mer­mans said.

DAVID GOLD­MAN THE AS­SO­CI­ATED PRESS

An ice­berg floats past By­lot Is­land in the Cana­dian Arc­tic ar­chi­pel­ago last sum­mer.

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