AMOC collapse: Scientists issue open letter warning on catastrophic risk of Atlantic ocean circulation collapse

Risk of Collapse of Ocean Circulation (AMOC) underestimated: Continued greenhouse gas emissions could trigger a regional cooling around the North Atlantic warned the Icelandic Met Office

An Open Letter by Climate Scientists, including 3 Australian climate scientists, was presented to the Nordic Council of Ministers warning of AMOC collapse "risk has so far been greatly underestimated. Such an ocean circulation change would have devastating and irreversible impacts especially for Nordic countries, but also for other parts of the world."

Global impacts may include "a shift in tropical rainfall belts, reduced oceanic carbon dioxide uptake (and thus faster atmospheric increase) as well as major additional sea-level rise particularly along the American Atlantic coast, and an upheaval of marine ecosystems and fisheries"

A North Atlantic nasty surprise: AMOC slowing faster than expected

Atlantic Meridional Overturning Circulation slowing much faster than expected

It seems that the 2004 Hollywood blockbuster disaster movie The Day after Tommorrow, while highly exaggerated, had the seed of scientific fact based upon the possible disruption that could occur from the slowdown or catastrophic cessation of the Atlantic ocean Meridional Overturning Circulation (AMOC), also known as the thermohaline circulation or Great ocean conveyor belt.

A new study by Rahmstorf et al (2015) published in Nature Climate Change has found evidence for a slowdown of the overturning circulation. This is based upon multiple lines of observation suggesting that over recent decades the current system has been weaker than ever before in the last century, or even in the last millennium.

The Gulf Stream is part of this circulation system with warm waters, which are naturally lighter, flowing north, and responsible for the mild climate of north western Europe. In the sub-polar region these waters cool, become more dense, and sink to the bottom before they start flowing south along the ocean bottom towards the tropics, then the South Atlantic and the Southern Ocean. The conveyor belt of currents connects the Atlantic, Indian, Pacific and Southern Oceans providing heat transfer and mixing throughout the globe.

Related Links: What’s going on in the North Atlantic? at Realclimate Blog | New Research Shows Exceptional Slowdown In Major Atlantic Ocean Currents Greg Laden's Science Blog

Atlantic sea surface temperatures affect Antarctic climate change

A new source of warming has been found for Antarctica: the North Atlantic and tropical Atlantic Ocean.

Warm waters in the Pacific have been connected to warming in Antarctica, but this is the first time that a connection with the Atlantic Ocean sea surface temperatures has been made.

"Our findings reveal a previously unknown--and surprising--force behind climate change that is occurring deep in our southern hemisphere: the Atlantic Ocean," says Xichen Li, a doctoral student in NYU's Courant Institute of Mathematical Sciences and the study's lead author. "Moreover, the study offers further confirmation that warming in one region can have far-reaching effects in another."

Global warming in recent decades has caused dramatic warming of the Antarctic Peninsula and West Antarctica. Changes in Antarctic climate have been attributed to greenhouse gas emissions and the ozone hole , sea surface temperatures in the central tropical Pacific warming (Qinghua Ding et al 2011) and the impact of El Nino.