Atlantic meridional overturning circulation
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The Atlantic meridional overturning circulation (AMOC) is a system of currents in the Atlantic Ocean, characterized by a northward flow of warm, salty water in the upper layers of the Atlantic, including the Gulf Stream, and a southward flow of colder, deep waters that are part of the Thermohaline circulation. The AMOC is an important component of the Earth’s climate system.
This ocean current system transports a substantial amount of heat energy from the tropics and Southern Hemisphere toward the North Atlantic, where the heat is then transferred to the atmosphere. Changes in this ocean circulation could have a profound impact on many aspects of the global climate system.
There is growing evidence that fluctuations in Atlantic sea surface temperatures, hypothesized to be related to fluctuations in the AMOC, have played a prominent role in significant climate fluctuations around the globe on a variety of time scales.
Measurements across the North Atlantic suggest multidecadal swings in sea surface temperatures that may be at least in part due to fluctuations in the AMOC. The figure below describes this variation in North Atlantic sea surface temperatures for the period 1856 to 2009. The repetitive cycle obvious in this figure is known as the Atlantic Multidecadal Oscillation (AMO). Evidence from paleorecords suggests that there have also been large, decade-scale changes in the AMOC, particularly during glacial times. These abrupt changes have had a profound impact on climate, both locally in the Atlantic and in remote locations around the globe.
At its northern boundary, the AMOC interacts with the circulation of the Arctic Ocean. The summer Arctic sea ice cover has undergone dramatic retreat since satellite records began in 1979, amounting to a loss of almost 30% of the September ice cover in 29 years. Climate model simulations suggest that rapid and sustained September Arctic ice loss is likely in future 21st century climate projections.
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- Sévellec, Florian; Fedorov, Alexey V.; Liu, Wei (August 2017). "Arctic sea-ice decline weakens the Atlantic Meridional Overturning Circulation". Nature Climate Change. 7 (8): 604–610. doi:10.1038/nclimate3353. ISSN 1758-678X.