In the Ocean, Clues to Change

http://www.nytimes.com/2014/08/12/science/in-the-ocean-clues-to-change.html?_r=0

Justin Gillis
Aug. 11, 2014

A few weeks ago, some 300 miles off the coast of New Zealand, scientists aboard the research vessel Tangaroa gently lowered two funky-looking orange orbs into the sea. Soon they disappeared, plunging of their own accord toward the depths of the Pacific Ocean.

They were prototypes, specialized robots designed to record temperature and other conditions all the way to the sea bottom, more than three miles down. Every few days since that June voyage, they have been surfacing, beaming their data to a satellite, then diving again.

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In fact, global warming has not stopped. The greenhouse gases released by humans are still trapping heat, and the vast bulk of it is being absorbed by the ocean, as has always been the case. Researchers have deployed more than 3,000 robotic floats that can measure the temperature in the upper layers of the ocean, and they show continual warming there.

This documented ocean warming is hard evidence that scientists have gotten the basic story right when it comes to the effects of human emissions. It is also a problem in itself, because water expands as it heats up, so the warming is a major factor behind the rise of sea level — which, in turn, has worsened flooding from storms like Hurricane Sandy.

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Despite the oceanic heating, it is true that at the surface of the planet, the increase of temperature has slowed quite a bit from the torrid pace of earlier decades. That has been a surprise, and trying to understand it has become an intense scientific focus.

The natural variability of climate could be playing a big role. ...

Another possibility, as strange as it may sound, is that the rapid rise of coal burning in China has temporarily slowed planetary warming. Coal releases greenhouse gases that will have a long-term warming effect, of course, but it also throws particles into the air that can reflect sunlight back to space over the short term.

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Some scientists think the deep ocean is playing a significant role, absorbing heat that would otherwise be showing up at the surface. And the available evidence suggests this is the case, but measurements of the deep ocean are scant.

That is where the prototype robotic floats, developed at the Scripps Institution of Oceanography, come in.

The idea is to supplement the older robots that are already prowling the ocean. That system, known as Argo, is one of the scientific triumphs of the age, but even the most advanced of the floats can dive only a little more than a mile, so they miss the bottom half of the sea.

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