When you hear about climate change it's

most often about melting glaciers and sea ice, increasing frequency

of heatwaves and powerful storms. Maybe, just maybe, you'll hear

about the acidification of the oceans too. What you don't hear about

is the saltiness of the seas. But that's changing too, according to a

new piece of research just published in Geophysical Research Letters

(see the abstract and figures).

The saltiness, or salinity, of the

oceans is controlled by how much water is entering the oceans from

rivers and rain versus how much is evaporating; what my kids

recognize as “The Water Cycle.” The more sunshine and heat there

is, the more water can evaporate, leaving the salts behind in higher

concentrations in some places. Over time, those changes spread out as

water moves, changing the salinity profiles of the oceans.

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Oceanographers from Scripps Institution of Oceanography and Lawrence

Livermore National Laboratory fingerprinted salinity changes from

1955 to 2004 from 60 degrees south latitude to 60 degrees north

latitude and down to the depth of 700 meters in the Atlantic, Pacific

and Indian oceans. They found salinity changes that matched what they

expected from such natural changes as El Niño or volcanic eruptions

(the latter can lower evaporation by shading and cooling the



the ocean data was compared to 11,000 years of ocean data generated

by simulations from 20 of the latest global climate models. When they

did that they found that the changes seen in the oceans matched those

that would be expected from human forcing of the climate. When they

combined temperature changes with the salinity, the human imprint is

even clearer, they reported.


“These results add to the evidence

that human forcing of the climate is already taking place, and

already changing the climate in ways that will have a profound impact

on people throughout the world in coming decades,” the oceanographers


That the oceans are often left out of

climate change talk is surprising considering the fact that oceans

cover more than 70 percent of the planet and so should logically be

expected to show the effects of our excessive releases of carbon

dioxide over the last 150 years or so.

Image: A NASA animation shows the global

movement of Earth's ocean surface currents from June 2005 to December

2007. The animation was created using data from NASA satellites, direct

ocean measurements and a numerical model developed by NASA JPL and the

Massachusetts Institute of Technology. Image credit: NASA/SVS