Oceans Getting Hotter Than Anybody Realized

Research published Sunday concluded that the upper 2,300 feet of the Southern Hemisphere’s oceans may have warmed twice as quickly after 1970 than had previously been thought.  Gathering reliable ocean data in the Southern Hemisphere has historically been a challenge, given its remoteness and its relative paucity of commercial shipping, which helps gather ocean data. Argo floats and satellites are now helping to plug Austral ocean data gaps, and improving the accuracy of Northern Hemisphere measurements and estimates.

“The Argo data is really critical,” said Paul Durack, a Lawrence Livermore National Laboratory researcher who led the new study, which was published in Climate Nature Change.  “The estimates that we had up until now have been pretty systematically underestimating the likely changes.”

Durack and Lawrence Livermore colleagues worked with a Jet Propulsion Laboratory scientist to compare ocean observations with ocean models.  They concluded that the upper levels of the planet’s oceans — those of the northern and southern hemispheres combined — had been warming during several decades prior to 2005 at rates that were 24 to 58 percent faster than had previously been realized.
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Ocean warming is exacerbating flooding caused by the melting of glaciers and other ice.  Seas have risen 8 inches since the industrial revolution, and they continue to rise at a hastening pace, worsening floods and boosting storm surges near shorelines around the world.  Another 2 to 7 feet of sea level rise is forecast this century, jeopardizing the homes and neighborhoods of the 5 million Americans who live less than 4 feet above high tide, as well as those of the hundreds of millions living along coastlines in other countries.

The other ocean temperature study, also published Sunday in Climate Nature Change, used Argo and other data to tentatively conclude that all of the ocean warming from 2005 to 2013 had occurred above depths of 6,500 feet.  During the same period, the Jet Propulsion Laboratory scientists who wrote the paper concluded, the expansion of those warming waters caused a third of the planet’s 2.8 millimeters of annual sea-level rise.

Steve Rintoul, a researcher at Australia’s Commonwealth Scientific and Industrial Research Organisation, or CSIRO, said findings of ocean warming above 6,500 feet in the Jet Propulsion Lab’s study explain the recent slowdown in warming at the Earth’s surface, which is sometimes called global warming hiatus, or warming pause.

Oceans Getting Hotter Than Anybody Realized