The Potential for Abrupt Change in the Atlantic Meridional Overturning Circulation
Posted by Doorman on 4/19/2011, 8:25 pm
Posted on this last season
Imho---- this is a must read!!!!


http://downloads.climatescience.gov/sap/sap3-4/sap3-4-final-report-ch4.pdf





The Atlantic Meridional Overturning Circulation (AMOC) is an important component of the Earth's climate
system, characterized by a northward flow of warm, salty water in the upper layers of the Atlantic, and a
southward flow of colder water in the deep Atlantic. This ocean circulation system transports a substantial
amount of heat from the Tropics and Southern Hemisphere toward the North Atlantic, where the heat is
transferred to the atmosphere. Changes in this circulation have a profound impact on the global climate
system, as indicated by paleoclimate records. These include, for example, changes in African and Indian
monsoon rainfall, atmospheric circulation of relevance to hurricanes, and climate over North America and
Western Europe. In this chapter, we have assessed what we know about the AMOC and the likelihood of
future changes in the AMOC in response to increasing greenhouse gases, including the possibility of abrupt
change. We have five primary findings:
It is very likely that the strength of the AMOC will decrease over the course of the 21st century in
response to increasing greenhouse gases, with a best estimate decrease of 25-30%.
Even with the projected moderate AMOC weakening, it is still very likely that on multidecadal to
century time scales a warming trend will occur over most of the European region downstream of the
North Atlantic Current in response to increasing greenhouse gases, as well as over North America.
No current comprehensive climate model projects that the AMOC will abruptly weaken or collapse in
the 21st century. We therefore conclude that such an event is very unlikely. Further, an abrupt collapse
of the AMOC would require either a sensitivity of the AMOC to forcing that is far greater than current
models suggest or a forcing that greatly exceeds even the most aggressive of current projections (such
as extremely rapid melting of the Greenland ice sheet). However, we cannot completely exclude either
possibility.



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The Potential for Abrupt Change in the Atlantic Meridional Overturning Circulation - Doorman, 4/19/2011, 8:25 pm
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