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Rapid Cooling In North Atlantic May Cause Disruptive Climate Change

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A serious climate change threat is looming in the region around the Atlantic Ocean, according to a new study.

It says an important area in the North Atlantic will be turning cool and freeze in a span of 10 years within this century. The probability is 50 percent, and such changes will be a fallout of the disruption caused to the oceanic current called Meridional Overturning Circulation, or MOC.

As a result, the worst hit will be the relatively warmer climate prevailing in northwest Europe, where an average 5C warmth exists, unlike other parts. Such a comfortable climate might become a casualty faster than envisaged.

Climate Models Relooked

Projecting a worst-case scenario, the study relooks many of the existing climate models, which had been too optimistic that the Atlantic Ocean current will not collapse for many centuries.

The consequences of the collapse of the key Atlantic ocean current were portrayed with a bit of exaggeration in the American movie The Day After Tomorrow showing the start of a new ice age after the MOC fails.

In deducing the results, the study adopted a different view on the future of Atlantic Ocean currents in contrast to the projections made by the Intergovernmental Panel on Climate Change's Fifth Assessment Report.

The study by researchers at the Environnements et Paléoenvironnements Océaniques et Continentaux laboratory of the University of Bordeaux in France along with Southampton University used a new algorithm in analyzing the 40 climate models of IPCC.

The findings have been published in the Nature Communications.

Slowing Of Ocean Current MOC

The slowdown of MOC has already been suggested by some studies. The ocean current, also called as the thermohaline circulation, is the force behind the warm Gulf Stream connecting Florida and European shores.

There is high concern that a drastic slowing of MOC would be disruptive to the entire climate system.

Unlike the IPCC models that suggest the MOC slowdown as a gradual process, the new study sees a high likelihood of rapid cooling in the North Atlantic within this century.

Cooling Of Labrador Sea

The climate projections of another study by oceanographers at EU emBRACE examined 40 models of IPCC and studied the temperature variations with specific reference to the northwest of the North Atlantic.

Their study with special focus on the Labrador Sea was significant, as it feeds the MOC as a convection system.

During winter, the surface water temperatures at the Labrador Sea plunges, and the water sinks after density rises. As a result, deep waters are displaced, which rise up and bring the heat to the surface to prevent ice cap formation, thus sustaining the warm current.

In the 40 climate models, seven predicted a total shutdown of the convection stream highlighting an abrupt cooling of the Labrador Sea by 2C to 3C in less than 10 years. The consequence will be the drastic lowering of North Atlantic coastal temperatures.

Stratification Factor

In analyzing the Labrador Sea as a case study, ocean stratification was considered as a vital parameter that activates winter convection because only a few models of IPCC suggested the snapping of MOC.

All the climate models that considered stratification factor predicted a rapid drop in North Atlantic temperatures. Researchers are waiting to validate their projections against the real data from the OSnap project, which is anchoring scientific tools in the sub-polar gyre, a large system of circulating ocean currents.

Affirming that North Atlantic waters may cool rapidly in the years to come, the team wants climate change adaptation policies for the regions around the North Atlantic to tackle the fallout of the phenomenon.

Impact On Regional Climate

The MOC, as a colossal conveyor belt, takes warm water from the South Atlantic along the ocean surface to the North Atlantic and takes a U-turn near Greenland.

There, the current's cold water sinks and flows southward into the South Atlantic. A loop of MOC keeps northwestern Europe warm and accelerates rainfall in the tropical Atlantic.

The impact of global warming in the North Atlantic is manifested by the way it affects the waters. Warming makes the waters less dense and takes away the ability to sink, forcing a further slowdown of MOC.

There is a theory that the current's speed will be restored by the infusion of rain-freshened water from the Southern Ocean into the Atlantic Ocean. If MOC weakens, the freshwater flow becomes tardy, and Atlantic water will turn saltier. Similar to cold water, salt water is also dense and can sink to the bottom, pushing up deep water to recover the MOC.

But the reality is freshwater is flowing from the Atlantic into the Southern Ocean, not the other way around. When the flow of warm water to the north becomes skewed, countries such as England and Iceland will chill despite the increase in carbon dioxide and greenhouse gasses.

When MOC slows, freshwater flows from the Atlantic to the Southern Ocean will also reduce Atlantic's saltiness, which will only hasten the collapse of the MOC.

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