Thursday, April 12, 2018

Atlantic ‘Conveyor Belt’ Has Slowed by 15% Since Mid-20th Century

Trends in sea surface temperatures. Left: in the climate model CM2.6 in a scenario with a doubling of the amount of CO2 in the air. Right: in the observation data from 1870 to the present day. In order to make the trends comparable despite the different periods and CO2 increases, they were divided by the globally averaged warming trend, i.e. all values above 1 show an above-average warming (orange-red), values below 1 a below-average warming, negative values a cooling. Due to the limited availability of ship measurements, the measurement data are much more “blurred” than the high-resolution model data. (Graph Credit: Levke Caesar) Click to Enlarge.
The Atlantic Ocean current that brings warm water up to Europe from the tropics has weakened by 15% since the middle of the last century, new research suggests.

Two studies, published in the journal Nature, use different approaches to show that the “Atlantic Meridional Overturning Circulation” (AMOC) is in a weaker state now than it has been for decades – and possibly even centuries.

The two studies differ on when and how they think the weakening was triggered. While one suggests it began in the mid-20th century as a response to human-caused climate change, the second proposes that it began a hundred years earlier following a natural shift in regional climate.

Despite the debate on when the weakening started, the studies agree that there has been a “continued decline in AMOC over the 20th century that may be attributed to recent global warming and melting of the Greenland ice sheet”, one author tells Carbon Brief.

Read more at Atlantic ‘Conveyor Belt’ Has Slowed by 15% Since Mid-20th Century

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