The Atlantic Ocean current system

11 Aug 2021 The Atlantic Ocean current system

Posted at 10:45h in Daily current-affairs by rahul123 0 Comments

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Context:

According to research published this week in Nature Climate Change, the Atlantic Meridional Overturning Circulation (AMOC) is losing its stability. AMOC is expected to diminish over the next century, according to the IPCC’s Report (AR6), which was issued on August 9.

About:
Atlantic Meridional Overturning Circulation (AMOC):

The AMOC is a massive ocean current system. It’s the Atlantic arm of the ocean conveyor belt, also known as the Thermohaline circulation (THC), which transports heat and nutrients throughout the world’s ocean basins.

AMOC transports warm tropical surface waters to the Northern Hemisphere, where they cool and sink. As a bottom current, it returns to the tropics and eventually to the South Atlantic. The Antarctic circumpolar circulation distributes it to all ocean basins from there.

Impact if AMOC collapses:

The Gulf Stream, which is part of the AMOC, is a warm stream that is responsible for the pleasant temperature along North America’s eastern coast as well as Europe. Europe will be quite chilly without a functioning AMOC and Gulf Stream.
An AMOC shutdown would chill the northern hemisphere and reduce rainfall across Europe, according to modeling research. It could also have an impact on El Nino.
“AMOC collapse brings about large, markedly different climate responses: a prominent cooling over the northern North Atlantic and neighboring areas, sea ice increases over the Greenland-Iceland-Norwegian seas and to the south of Greenland, and a significant southward rain-belt migration over the tropical Atlantic,” according to a 2016 paper in Science Advances.
The research team thought that earlier models underestimated the AMOC’s stability because they ignored the impact of freshwater. Because freshwater from melting Greenland ice sheets and the Arctic area is not as thick as salt water and does not settle to the bottom, it might weaken circulation.

Has the AMOC ever weakened?

The intensity of AMOC and THC has historically fluctuated, especially during the late Pleistocene era (last 1 million years). Extreme glacial phases have witnessed poorer circulation and a slowing in AMOC, whereas glacial terminations have seen higher circulation and AMOC.
Paleoclimate proxies such as sea surface temperatures (SST), salinity, and isotope fingerprints from single-celled creatures called foraminifera are used to learn about historical variations. However, the changes seen in the last 100-200 years are anthropogenic, and these rapid shifts are destabilizing the AMOC, putting the system at risk of collapse.
Researchers reported in February that AMOC is at its lowest point in over a millennium. The researchers looked at how AMOC has changed over the last 1600 years. According to the findings, it [AMOC] was reasonably steady until the late nineteenth century. Ocean currents began to diminish after the Little Ice Age ended around 1850, with a second, more dramatic reduction occurring since the mid-twentieth century.

The reason behind slowing down of AMOC:

• Climate models have indicated for a long time that global warming will damage the world’s major ocean systems. Last month, scientists discovered that a section of the Arctic ice known as the “Last Ice Area” had also melted. The freshwater from melting ice lowers the water’s salinity and density. The water is now unable to sink as quickly as it formerly did, weakening the AMOC flow.
According to 2019 research, the Indian Ocean may also be assisting in the slowdown of AMOC. According to the experts, when the Indian Ocean heats quicker and faster, it produces more precipitation. With so much precipitation in the Indian Ocean, the Atlantic Ocean will get less precipitation, resulting in increased salinity in the Atlantic’s tropical waters. This saltier Atlantic water, when it travels north via the AMOC, will get colder and sink faster than usual.

Source: The Indian Express
Syllabus: GS1 (Geography)