Context:
A recent study reveals the impact of collapse of Atlantic Meridional Overturning Circulation.
Atlantic Meridional Overturning Circulation (AMOC):
- What is it? – AMOC is defined as the northward flow of warm, salty water in the upper layers of the Atlantic, and a southward flow of colder, deep waters that are part of the thermohaline circulation.
- Thermohaline Circulation – The process whereby deep-ocean currents are driven by differences in the water’s density, which is controlled by temperature (thermo) and salinity (haline).
- Working of AMOC –
- 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.
- Importance –
- Aids in distributing heat and energy around the earth, acting as a Heat Conveyor Belt
- Western Europe’s climate is less harsh even in winters because of AMOC (Gulf Stream, North Atlantic Drift).
- Concern – More fresh cold water is added to the North Atlantic Ocean due to increased precipitation and rapid melting of the Greenland ice sheet, which is reducing salinity and density of the water.
- The colder layer of the ocean is expanding and the warmer layer is contracting lead to collapse of AMOC.
Impact of slow down
May be the first of the 16 climate tipping elements to be breached.
- Create a Domino Effect whereby the collapse of AMOC will impact other tipping elements and climate systems globally.
- Atlantic Meridional Overturning Circulation (Tipping element) – A system of ocean currents that brings warm water from the equator to the northern latitudes and takes back cold water. This helps moderate the climate of Europe and North America and its collapse could lead to colder and stormier weather in the two continents.
- Amazon rainforest (Tipping element) – AMOC collapse means more heat in tropics, Amazon could either stabilise or turn dry
- Sahel/West African monsoon (Tipping element) – Impact on wind flow, Inter Tropical Convergence Zone (ITCZ) by AMOC collapse may hurt establishment of monsoon
- Indian Summer Monsoon – Impact on wind flow, ITCZ by AMOC collapse may hurt establishment of monsoon
Tipping Elements
Tipping elements – Large-scale systems that influence the planet’s climate and ecology, which are changing due to warming and accumulation of greenhouse gases in the atmosphere from anthropogenic emissions.
Source: Down To Earth
Previous Year Question
In the South Atlantic and South-Eastern Pacific regions in tropical latitudes, cyclones do not originate. What is the reason?
[UPSC Civil Service Exam – 2015 Prelims]
(a) Sea surface temperatures are low
(b) Inter-Tropical Convergence Zone seldom occurs
(c) Coriolis force is too weak
(d) Absence of land in those regions
Answer: (b)
