Recently released IPCC’s sixth assessment report has confirmed all the doubts and shattered all myths related to climate change.
It has precariously underlined the shortcomings in our approach for some concerted action and calculated the real events coming out as recalcitrant offshoots of the Climate change.
While it forecasts of reduced efficiency of our global carbon sinks, we are pretty sure that one of the biggest carbon sinks has begun acting weird: the world Oceans.
As per a study published in Nature Climate Change, Atlantic Meridional Overturning Circulation (AMOC) which is part of a larger system of ocean currents, known as the Gulf Stream, is losing its centuries’ old stability.
The threatening IPCC report has also speculated that the AMOC will see a decline over the 21st century.
Ocean currents flow like vast rivers, along their respective predictable paths in form of waves and tides. While some ocean currents flow at the surface; others may flow deep within water.
Acting as conveyor belt of the planet or thermohaline circulation, these undertake distribution, balancing and re-establishing the Earth’s governance over its processes to sustain life.
It helps the planet in controlling temperatures and sustaining oceanic life by transporting nutrients and food to the organisms. AMOC is indeed the largest carbon sink in complete Northern Hemisphere.
These water currents, unlike rivers, get driven by winds, under the influence of Earth’s rotation and world geography like restrictions by coastlines along with the differences in salinity, density and even temperatures.
The Gulf stream transports warm water from the tropic northwards into the colder regions of North Atlantic. Due to this warm effect of the Gulf Stream along with an associate North Atlantic Drift, ports lying in these latitudes remain ice-free for operations, even in extreme winters.
But as the warm water flows northwards, it cools and some additional evaporation occurs, increasing the amount of salt.
Low temperature around with a high salt content makes the water denser, which then sinks deep into the ocean. This cold, dense water slowly spreads southwards, completing gyres across several kilometers below the surface.
What can happen if the Gulf Stream collapses?
The movie Day after Tomorrow could well portray the disastrous effects on North Atlantic Ocean circulation going awry.
A 2016 research paper explained well: “AMOC collapse brings about large, markedly different climate responses: a prominent cooling over the northern North Atlantic and neighbouring 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.”
Therefore, such a shutdown would cool our northern hemisphere beyond sustenance and tend to decrease rainfall over entire European landmass. Growing further, it may endanger El Nino, responsible for heating certain regions of the planet.
This new revelation has come to the forefront after taking into account, the freshwater from now melting Greenland ice sheets which makes the circulation weaker. “Last Ice Area” the core Arctic glacier has also melted last month in the wake of human activities.
This melting happens because the freshwater has lesser density than the saltwater and doesn’t sink to the bottom.
A participant of the study explains: “(The) combined evidence makes it plausible that a critical transition to the weak mode may occur in response to rising temperatures and North Atlantic freshwater inflow.”
Cases confirming this study:
According to a climate expert: “I think it’s a really dramatic example of the urgency with which we are now approaching climate change impacts properly described as “tipping points”.
Scientists have found a cold spot called the Cold Blob in the waters south of Greenland, where the waters have been cooling as evident instead of warming indicating the weakening of Gulf Stream as it is no longer traveling into that region, unfreezing lives.
Another area in South Atlantic is witnessing rising salinity levels as evidence of the southern part of the system slowing down considerably.
Has this happened before?
AMOC and other thermohaline circulations’ strengths have always been fluctuating, especially through the late Pleistocene time period around 1 million years ago.
“The extreme glacial stages have seen weaker circulation and slowdown in AMOC, while the glacial terminations have shown a stronger AMOC and circulation.”
The circulations had been relatively stable across the 19th century.
“We know about these past fluctuations by studying paleoclimate proxies such as sea surface temperatures (SST), salinity, and isotope signatures from single-celled organisms called foraminifera. But the changes we experience in the last 100-200 years are anthropogenic, and these abrupt changes are destabilizing the AMOC, which could collapse the system.”
India and the story of AMOC:
As the Indian Ocean warms with the advent of Climate change, it triggers an additional precipitation. With an increased precipitation in the Indian Ocean, there will be less induced precipitation in the Atlantic.
This will lead to increased salinity in the waters of the tropical regions encompassing the Atlantic. This saltier water with an increased density in the Atlantic will get colder and sink.
“If other tropical oceans’ warming, especially the Pacific, catches up with the Indian Ocean, the advantage for AMOC will stop”, explains the researchers.
“If we continue to drive global warming, the Gulf Stream System will weaken further – by 34 to 45 percent by 2100 according to the latest generation of climate models”.
Does this affect India in the long run?
This sort of Gulf Stream disturbances can be felt as far as India and other South Asian regions, as the circulation strengthens Indian monsoons and intermingles with several other important currents in the Indian Ocean.
Any further destabilization will certainly cause trickles in the monsoons, which will be more erratic, aided with bigger storms, intense droughts and at times heavier rainfall in shorter amounts of time.
The mesh of circulations across the world is a complicated system for which the answers don’t come easy.
Nobody can estimate when we could land in trouble. It could swift through a century or may not survive even a decade, but it has proven to be inevitable. The Scientists have warned that this must not happen at any cost and shall be evaded.
The study participant adds: “So the only thing to do is keep emissions as low as possible. The likelihood of this extremely high-impact event happening increases with every gram of CO2 that we put into the atmosphere”.