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NeoGreen

(4,030 posts)
Mon May 7, 2018, 08:56 AM May 2018

Disrupting the deep: Ocean warming reaches the abyss

https://www.earthmagazine.org/article/disrupting-deep-ocean-warming-reaches-abyss


The stable pattern of global ocean circulation is known as meridional overturning circulation and is driven by density gradients that are strongly affected by changes in heat and freshwater input. Credit: K. Cantner, AGI.


Disrupting the deep: Ocean warming reaches the abyss
By Kate S. Zalzal

Seventy-one percent of our planet is covered by ocean, and these basins contain 97 percent of Earth’s near-surface water. The ocean lies at the heart of the global climate system, shaping all parts of our environment, even in the deepest continental interiors. So as the ocean goes, so goes the planet — and the ocean is warming.

Since the 1970s, just 7 percent of the heat associated with human-caused warming has gone to melting snow and ice or to warming the land surface and atmosphere. The remaining 93 percent of the heat has been absorbed by the ocean. Temperatures are increasing at nearly all latitudes and depths within the ocean. In 2016, both the global average atmospheric and sea-surface temperatures were the highest on record — the third consecutive year this milestone was reached — with sea-surface temperatures 0.75 degrees Celsius higher than the 20th-century average. And the warming trend is expected to continue, with mean global ocean temperatures predicted to increase by an additional 1 to 4 degrees Celsius by 2100.

The effect of this heat on the ocean, and what it means for the future, has gained widespread attention only in the last decade or so. Given the size of the ocean, and the time and cost associated with ship-based data acquisition, scientific understanding of many heat-related processes in the ocean has grown slowly, says Sarah Purkey, an oceanographer at Scripps Institution of Oceanography. But it’s clear that the ocean is changing. Sea level is rising, sea ice is melting, and ice shelves and glaciers are destabilizing. Ocean warming is also dramatically affecting marine biogeochemistry, with increases in deoxygenated dead zones and ocean acidification.
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