Not just land heat waves: Oceans are in hot wa­ter too

South Florida Sun-Sentinel (Sunday) - - Nation & World - By Christina Lar­son As­so­ci­ated Press

WASHINGTON — Even the oceans are break­ing tem­per­a­ture records in this sum­mer of heat waves.

Off the San Diego coast, sci­en­tists ear­lier this month recorded all-time high sea­wa­ter tem­per­a­tures since daily mea­sure­ments be­gan in 1916.

“Just like we have heat waves on land, we also have heat waves in the ocean,” said Art Miller of the Scripps In­sti­tu­tion of Oceanog­ra­phy.

From 1982 to 2016, the num­ber of “ma­rine heat waves” roughly dou­bled, and likely will be­come more com­mon and in­tense as the planet warms, a study re­leased last week found. Pro­longed pe­ri­ods of ex­treme heat in the oceans can dam­age kelp forests and coral reefs, and harm fish and other ma­rine life.

“This trend will only fur­ther ac­cel­er­ate with global warm­ing,” said Thomas Frolicher, a cli­mate sci­en­tist at the Univer­sity of Bern in Switzer­land, who led the re­search.

His team de­fined ma­rine heat waves as ex­treme events in which sea-sur­face tem­per­a­tures ex­ceeded the 99th per­centile of mea­sure­ments for a given lo­ca­tion. Be­cause oceans both ab­sorb and re­lease heat more slowly than air, most ma­rine heat waves last for at least sev­eral days — and some for sev­eral weeks, said Frolicher. Many sea creatures have evolved to sur­vive within a fairly nar­row band of tem­per­a­tures com­pared to creatures on land, and even in­cre­men­tal warm­ing can be dis­rup­tive.

Some free-swim­ming sea an­i­mals like bat rays or lob­sters may shift their rou­tines. But sta­tion­ary or­gan­isms like coral reefs and kelp forests “are in real peril,” said Michael Bur­rows, an ecol­o­gist at the Scot­tish Ma­rine In­sti­tute, who was not part of the re­search.

In 2016 and 2017, per­sis­tent high ocean tem­per­a­tures off eastern Aus­tralia killed off as much as half of the shal­low wa­ter corals of the Great Bar­rier Reef — with sig­nif­i­cant con­se­quences for other creatures de­pen­dent upon the reef.

“One in ev­ery four fish in the ocean lives in or around coral reefs,” said Ove HoeghGuld­berg, a ma­rine bi­ol­o­gist at the Univer­sity of Queens­land. “So much of the ocean’s bio­di­ver­sity de­pends upon a fairly small amount of the ocean floor.”

The lat­est study in Na­ture re­lied on satel­lite data and other records. Warm ocean tem­per­a­tures dis­rupted the food sup­ply for many species, in­clud­ing ma­rine mam­mals.


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