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Even the deepest, coldest parts of the ocean are getting hotter

Things heat up on the seabed.

Thermometers moored to the bottom of the Atlantic Ocean have recorded an average temperature rise of about 0.02 degrees Celsius over the past decade, researchers report in their Sept. 28 geophysical research chart. That warming may be a consequence of human-driven climate change, which has increased the temperature of the ocean near the surface (SN: 25/09/19), but it is unclear as little is known about the deeper, darker parts of ocean.

“The deep ocean, below about 2,000 meters, is not very well observed,” says Chris Meinen, oceanographer at the U.S. National Oceanic and Atmospheric Administration in Miami. The deep sea is so hard to reach that the temperature at a given research site is usually only taken once a decade. But Meinen’s team measured temperatures by the hour from 2009 to 2019 using seabed sensors at four points in the Argentine basin, off the coast of Uruguay.

Temperature records of the two deepest points revealed a clear warming trend during that decade. The waters at 4,540 meters below the surface warmed from an average of 0.209 ° C to 0.234 ° C, while the waters of 4,757 meters dropped from about 0.232 ° C to 0.248 ° C. This warming is much weaker than in the upper ocean. , says Meinen, but also notes that as warm water rises, it would need a lot of heat to generate even this little bit of deep warming.

It’s too early to judge whether human activity or natural variation is the cause, Meinen says. Continuing to monitor these sites and comparing records with device data in other ocean basins can help clarify things.

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