Antarctic overturning circulation
- May 29, 2023
- Posted by: OptimizeIAS Team
- Category: DPN Topics
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Antarctic overturning circulation
Subject : Geography
Section: Climatology
Concept :
- Antarctica sets the stage for the world’s greatest waterfall. The action takes place beneath the surface of the ocean.
- Here, trillions of tonnes of cold, dense, oxygen-rich water cascade off the continental shelf and sink to great depths.
- This Antarctic “bottom water” then spreads north along the sea floor in deep ocean currents, before slowly rising, thousands of kilometres away.
- In this way, Antarctica drives a global network of ocean currents called the “overturning circulation” that redistributes heat, carbon and nutrients around the globe. The overturning is crucial to keeping Earth’s climate stable. It’s also the main way oxygen reaches the deep ocean.
- But there are signs this circulation is slowing down and it’s happening decades earlier than predicted. This slowdown has the potential to disrupt the connection between the Antarctic coasts and the deep ocean, with profound consequences for Earth’s climate, sea level and marine life.
Atlantic Meridional Overturning Circulation (AMOC)
- The Atlantic Meridional Overturning Circulation (AMOC) is a major ocean current system that transports warm surface waters from the tropics toward the northern Atlantic and colder deep waters that are part of the thermohaline circulation, southward.
- One of the main ways the ocean circulates heat, salt, carbon, and nutrients throughout the world’s oceans is through overturning circulation.
What is thermohaline circulation?
- The thermohaline circulation, also known as the ocean’s conveyor belt, is part of the ocean circulation and is powered by temperature and salinity differences causing density differences. These are deep ocean currents occurring thousands of meters below the sea surface.
- It leads to intermixing of salt and heat. Thus, it effectively describes a driving mechanism.
Working of Atlantic Meridional Overturning Circulation
- The Atlantic Ocean’s warm water cools as it travels north, and evaporation raises its salt content.
- The water sinks deep into the ocean due to its increased density brought on by a combination of a low temperature and a high salt content.
- Deep below, the chilly, dense water steadily moves southward.
- It eventually returns to the surface, warms up once more, and the circulation is complete.
Significance of AMOC
- AMOC helps to disperse heat and energy throughout the earth (heat budget).
- Because of AMOC, the climate in Western Europe is less severe even during the winter (Gulf Stream, North Atlantic Drift).
- By absorbing and storing carbon from the atmosphere, it serves as a carbon sink.
- Carbon sequestration by AMOC has profound effects on how anthropogenic global warming develops.
- The distribution of heat to the polar regions is largely dependent on thermohaline circulation. As a result, it impacts how quickly sea ice forms at the poles, which in turn affects other components of the climate system (such as the albedo, and thus solar heating, at high latitudes).