Tuesday, December 30, 2014

Ocean Warming: Probing a Blue Abyss

A Weddell seal with a conductivity-temperature-depth tag on its head. (Credit: Dan Costa, University of California at Santa Cruz) Click to Enlarge.
For every 10 joules of energy that our greenhouse gas pollution traps here on Earth, about 9 of them end up in an ocean.  There, the effects of global warming bite into fisheries, ecosystems and ice.  But those effects are largely imperceptible to humans — as invisible to a landlubber as an albatross chomping on a baited hook at the end of a long line.
During 2014, as rising ocean heat fueled planetary temperature records, and as it continued to eat away at Antarctic ice, scientists discovered that the oceans have been warming far more quickly than anybody had realized — and doing so for decades.  Stark findings were published online in Nature Climate Change in October, relying on data from the global flotilla of thousands of Argo floats.  These drone-like seafarers have been plumbing inhospitable depths since 2000, beaming back data on ocean temperatures and other variables.

Using float data, scientists recalibrated sparse historical measurements and estimates of ocean warming, concluding that the upper 2,700 feet of the world’s oceans had warmed by between a quarter and a half more than had previously been realized.  The largest discrepancies with existing data were discovered in the Southern Hemisphere, where historical records are as sparse as the shipping traffic that traditionally provided so much of the planet’s ocean weather information.  There, it appears that ocean warming has been occurring at twice the previously-understood rate.

“We continue to be stunned at how rapidly the ocean is warming,” Sarah Gille, a Scripps Institution of Oceanography professor, said when we spoke with her earlier this year. “Extra heat means extra sea level rise, since warmer water is less dense, so a warmer ocean expands.”

As seas continue to swell, flooding cities and infrastructure, they’re also going to continue to become more acidic.

The impacts of ocean acidification, which is caused when carbon dioxide dissolves into seas and reacts with water, is a topic that scientists and governments are only just starting to grasp in meaningful ways.  With taskforces and research projects being launched across the globe, 2015 promises more answers not only on ocean warming, but on the shellfish-ravaging and fish-baffling effects of falling pH levels.

Read more at Ocean Warming: Probing a Blue Abyss

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