Tuesday, March 15, 2016

Livermore scientists find global ocean warming has doubled in recent decades


Public Release: 19-Jan-2016
Livermore scientists find global ocean warming has doubled in recent decades
DOE/Lawrence Livermore National Laboratory

Lawrence Livermore scientists, working with National Oceanic and Atmospheric Administration and university colleagues, have found that half of the global ocean heat content increase since 1865 has occurred over the past two decades.

"In recent decades the ocean has continued to warm substantially, and with time the warming signal is reaching deeper into the ocean," said LLNL scientist Peter Gleckler, lead author of a paper published in the journal Nature Climate Change.

Changes in ocean heat storage are important because the ocean absorbs more than 90 percent of the Earth's excess heat increase that is associated with global warming. The observed ocean and atmosphere warming is a result of continuing greenhouse gas emissions.


Increases in upper ocean temperatures since the 1970s are well documented and associated with greenhouse gas emissions. By including measurements from a 19th century oceanographic expedition and recent changes in the deeper ocean, the study indicates that half of the accumulated heat during the industrial era has occurred in recent decades, with about a third residing in the deeper oceans.


This study found that estimates of ocean warming over a range of times and depths agree well with results from the latest generation of climate models, building confidence that the climate models are providing useful information. "The year-round, global distribution of ocean temperature data collected by Argo has been key in improving our estimates of ocean warming and assessing climate models," notes LLNL oceanographer Paul Durack.

While Argo only samples the upper half of the ocean volume, pilot arrays of new "Deep Argo" floats that sample to the ocean floor are being deployed. This vast ocean volume in the deeper half is only measured infrequently by research vessels. Those deep data also show warming, even in the bottom layers of the ocean in recent decades.


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