Weakening of Atlantic meridional overturning circulation can have dramatic consequences for Europe and other parts of the Atlantic rim
While greenhouse warming caused by human activity is heating up the Indian oceans, it is likely to boost a key system of currents in the Atlantic Ocean, that plays a key role in determining the weather across the world, according to a new study.
Atlantic meridional overturning circulation (AMOC) — which is sometimes referred to as the “Atlantic conveyor belt” — is one of the Earth’s largest water circulation systems where ocean currents move warm, salty water from the tropics to regions further north, such as western Europe and sends colder water south.
It aids in distributing heat and energy around the earth, as the warm water it carries releases heat into the atmosphere, and in absorbing and storing atmospheric carbon.
For thousands of years, AMOC has remained stable, but since the past 15 years, it has been weakening — a development that could have dramatic consequences for Europe and other parts of the Atlantic rim, according to the study published in the journal Nature Climate Change.
Researchers from the Scripps Institution of Oceanography at the University of California-San Diego and Yale University found that rising temperatures in the Indian Ocean can help boost the AMOC and delay slow down.
Warming in the Indian Ocean generates additional precipitation, which, in turn, draws more air from other parts of the world, including the Atlantic.
The higher level of precipitation in the Indian Ocean will reduce precipitation in the Atlantic and increase salinity in the waters, the researchers explained.
This saline water in the Atlantic, as it comes north via AMOC, will get cold much quicker than usual and sink faster, acting “as a jump start for AMOC, intensifying the circulation”, said Alexey Fedorov from Yale.
However, scientists don't know for how long this enhanced warming in Indian Ocean will continue. “If other tropical oceans’ warming, especially the Pacific's, catches up with the Indian Ocean, the advantage for AMOC will stop,” Fedorov added.
Moreover, it isn't clear whether slowdown of AMOC is caused by global warming alone or it is a short-term anomaly related to natural ocean variability, said the researchers, emphasising the need to understand the importance of AMOC stability.
AMOC last witnessed a slow down 15,000 to 17,000 years ago. It caused “harsh winters in Europe, with more storms or a drier Sahel in Africa due to the downward shift of the tropical rain belt,” Fedorov said.
“The mere possibility that the AMOC could collapse should be a strong reason for concern in an era when human activity is forcing significant changes to the Earth’s systems,” Fedorov added.
To understand, the team analysed warming in the Indian Ocean. “Warming of the Indian Ocean is considered one of the most robust aspects of global warming,” said Shineng Hu from Scripps.
The finding exemplifies the intricate, interconnected nature of global climate, said the researchers.
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