Atlantic Meridional Overturning Current
In the Atlantic operates a large system of ocean currents, circulating the waters between the north and the south. Called Atlantic Meridional Overturning Current, or AMOC, it ensures the oceans are continually mixed, and heat and energy are distributed around Earth.
For the last 15 years, however, scientists have been worried by signs that AMOC may be slowing, which could have drastic consequences on global climate.
Now a new study suggests that AMOC is getting help from the Indian Ocean. Warming of Indian Ocean as a result of climate change is causing a series of cascading effects that is providing AMOC a “jump start”.
How AMOC works
On its website, the UK Met Office likens AMOC to a conveyor belt and explains how it works. As warm water flows northwards in the Atlantic, it cools, while evaporation increases its salt content. Low temperature and a high salt content raise the density of the water, causing it to sink deep into the ocean. The cold, dense water deep below slowly spreads southward. Eventually, it gets pulled back to the surface and warms again, and the circulation is complete. This continual mixing of the oceans, and distribution of heat and energy around the planet, contribute to global climate.
What is happening now
AMOC has been stable for thousands of years. Data since 2004, as well as projections, have given some scientists cause for concern. What is not clear, however, is whether the signs of slowing in AMOC are a result of global warming or only a short-term anomaly.
Indian Ocean’s role
Research has found that as the Indian Ocean warms faster and faster, it generates additional precipitation. This draws more air from other parts of the world to the Indian Ocean, including the Atlantic. With so much precipitation in the Indian Ocean, there will be less precipitation in the Atlantic Ocean. Less precipitation will lead to higher salinity in the waters of the tropical portion of the Atlantic — because there won’t be as much rainwater to dilute it. This saltier water in the Atlantic, as it comes north via AMOC, will get cold much quicker than usual and sink faster. This would act as a jump start for AMOC, intensifying the circulation.
Source: The Indian Express