Strange 'cold blob' in the middle of the Atlantic Ocean that is getting cooler as the rest of the world heats up is caused by shifting ocean currents and low-level clouds, study shows

A strange 'cold blob' in the Atlantic Ocean that is cooling as the rest of the world heats up is caused by shifting ocean currents and low-level clouds, a study found. 

The blob — or 'warming hole' — was first spotted in 2015 and has been connected to a weakening of the so-called Atlantic Meridional Overturning Circulation (AMOC).

However, analysis by researchers from Germany has revealed that the causes of the cooling blob are slightly more complicated — with many different factors at play.

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A strange 'cold blob' in the Atlantic Ocean (pictured in light blue) that is cooling as the rest of the world heats up is caused by shifting ocean currents and low-level clouds, a study found

The AMOC sees warm, salty waters transported northwards in the ocean's upper layers while colder waters near the pole sink are are carried south at depth.

As the AMOC carries heat from the tropics to the North Atlantic, it also has a vital role to play in affecting the climate and weather across Europe.

However, the melting of the Greenland ice sheet and increased rainfall in the region is preventing the cooler water from sinking, weakening the whole circulation. 

In their study, climate scientist Paul Keil of the Max Planck Institute for Meteorology in Hamburg and colleagues created long-term climate models to determine exactly which factors are contributing to the formation of the warming hole.

The team found that the relationship between the hole and the AMOC is highly dependant on the effect of greenhouse gases in the atmosphere.

Furthermore, modelling suggested that heat transport out of the hole is aided not only by the weakened AMOC but also by high latitude ocean circulation — or a 'gyre' — and an overturning of water north of the cold blob. 

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Analysis by researchers from Germany has revealed that the causes of the cooling blob are slightly more complicated, with many different factors at play — including the weakening of the Atlantic Meridional Overturning Circulation (shown in red) a sub-polar gyre (blue) and increased reflection of incoming solar radiation (yellow) through low-lying cloud formation

Simulations that considered the impact of the atmosphere alone — by modelling the AMOC without the weakening seen in real life — revealed that the formation of low-lying clouds as incoming warm waters cooled also play a role in the hole.

These clouds serve to reflect more incoming radiation from the Sun, helping to cool down the Earth's surface in the warming hole even more.

The full findings of the study were published in the journal Nature Climate Change.

ATLANTIC OCEAN CIRCULATION PLAYS A KEY ROLE IN REGULATING THE GLOBAL CLIMATE

When it comes to regulating global climate, the circulation of the Atlantic Ocean plays a key role.

This is due to a constantly moving system of deep-water circulation often referred to as the Global Ocean Conveyor Belt which sends warm, salty Gulf Stream water to the North Atlantic where it releases heat to the atmosphere and warms Western Europe.

The cooler water then sinks to great depths and travels all the way to Antarctica and eventually circulates back up to the Gulf Stream.

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When it comes to regulating global climate, the circulation of the Atlantic Ocean plays a key role

This motion is fuelled by thermohaline currents - a combination of temperature and salt.

It takes 1,000 years for water to complete a continuous journey around the world.

Researchers believe that as the North Atlantic began to warm near the end of the Little Ice Age, freshwater disrupted the system, called the Atlantic Meridional Overturning Circulation (AMOC).

Arctic sea ice, and ice sheets and glaciers surrounding the Arctic began to melt, forming a huge natural tap of fresh water that gushed into the North Atlantic.

This huge influx of freshwater diluted the surface seawater, making it lighter and less able to sink deep, slowing down the AMOC system.

Researchers found the AMOC has been weakening more rapidly since 1950 in response to recent global warming.