Sunday , October 2 2022

Ocean circulation in the North Atlantic is weakest in 1500 years and may trigger an ice age



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Researchers have discovered that water in the North Atlantic has "dramatically weakened".

The study shows that the levels are lowest in 1500 years – and climate change is owed.

Researchers warn the current will have a "deep impact" on both the North American and European climate.

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The Weakening Ocean: This is a schematic of the circulation in the West North Atlantic during the episode of strong (left) and weak (right) western transport of the Labrador Current (LC). Oceanography in this region is characterized by the interaction between the water masses formed in Labrador and moving west (LC and Labrador Sea Slope Water) and the water masses moving east from the Gulf Stream (GS) and its Atlantic Temperate Slope Water (ATSW). The exact location of these two water mass systems (yellow dashed lines) is determined by the strength of the northern recycle gun (white arrows), which then controls the temperature.

The Weakening Ocean: This is a schematic of the circulation in the West North Atlantic during the episode of strong (left) and weak (right) western transport of the Labrador Current (LC). Oceanography in this region is characterized by the interaction between the water masses formed in Labrador and moving west (LC and Labrador Sea Slope Water) and the water masses moving east from the Gulf Stream (GS) and its Atlantic Temperate Slope Water (ATSW). The exact location of these two water mass systems (yellow dashed lines) is determined by the strength of the northern recycle gun (white arrows), which then controls the temperature.

The Weakening Ocean: This is a schematic of the circulation in the West North Atlantic during the episode of strong (left) and weak (right) western transport of the Labrador Current (LC). Oceanography in this region is characterized by the interaction between the water masses formed in Labrador and moving west (LC and Labrador Sea Slope Water) and the water masses moving east from the Gulf Stream (GS) and its Atlantic Temperate Slope Water (ATSW). The exact location of these two water mass systems (yellow dashed lines) is determined by the strength of the northern recycle gun (white arrows), which then controls the temperature.

WHY IS OCEAN RUN SPECIAL?

Sea currents play an important role in regulating the planet.

The slower circulation in the North Atlantic can make profound changes both in the North American and European climate, but also in Dutch and Asian summer rainforests.

This transfer of heat and energy not only directly affects the climate across Europe and North America, but can affect the monsoon system of Africa and Asia through its effect on ocean surface temperature, hydrological cycle, atmospheric circulation and variation in the intertropical convergence zone.

Researchers studied the Atlantic Meridian Overturning Circulation (AMOC), branch of the North Atlantic circulation that brings warm surface water to the Arctic and cold deep water towards the equator.

The research, led by Drs. Christelle Not and Benoit Thibodeau from the Department of Geosciences and the Swire Institute for Marine Sciences, University of Hong Kong, are interpreted as a direct consequence of global warming and the associated melting of the Green Ice Lag.

The slower circulation in the North Atlantic can make profound changes both in the North American and European climate, but also in Dutch and Asian summer rainforests.

"AMOC plays a decisive role in regulating the global climate, but researchers are struggling to find reliable indicators of its intensity before.

"The discovery of this new record of AMOC will increase our understanding of its drivers and help us better understand potential near future changes during global warming," said Dr. Thibodeau.

The research group also found a weak signal during a period called the Little Ice Age (a cold spelling observed between about 1600 and 1850 AD).

WHAT WAS THE SMALL YEAR?

The reconstructed depth of the little ice age varies between different studies

The reconstructed depth of the little ice age varies between different studies

The reconstructed depth of the little ice age varies between different studies

The little ice age occurred between 1300 and 1850.

There were two stages of Little Ice Age, the first beginning around 1290 and continuing until the late 1400s.

It was a somewhat warmer period in the 16th century, after which the climate deteriorated significantly, with the coldest period between 1645 and 1715.

During this coolest phase of the Little Ice Age there is evidence that average winter temperatures in Europe and North America were as much as 2 ° C lower than presently.

The Baltic Sea froze over, like many of the rivers and lakes in Europe.

The Frozen Thames, 1677, an original painting in the collection of the Museum of London

The Frozen Thames, 1677, an original painting in the collection of the Museum of London

The Frozen Thames, 1677, an original painting in the collection of the Museum of London

The winters were bitterly cold and summers were often cool and wet.

These conditions led to extensive plant defects, famine and population decline.

There were increased levels of social concern as large sections of the population were reduced to starvation and poverty.

Although not as pronounced as the 20th century, the signal can confirm that this period was also characterized by a weaker circulation in the North Atlantic, which means a reduction in the transfer of heat to Europe, which contributes to the cold temperature of this temperature.

But more work is needed to validate this hypothesis.

"While we could base the truth about our 20-century temperature reconstruction against instrumental measurement, it's not possible to do it for the Little Ice Age period.

"Therefore, we need to do more analysis to consolidate this hypothesis," says Dr. Note.

The results were recently published in the prestigious journal Geophysical Research Letters.

Atlantic Meridional Overturation Circulation (AMOC) is the branch of the North Atlantic circulation that provides hot surface water against the Arctic and cold deep water against the equator.

This transfer of heat and energy not only directly affects the climate across Europe and North America, but can affect the monsoon system of Africa and Asia through its effect on ocean surface temperature, hydrological cycle, atmospheric circulation and variation in the intertropical convergence zone.

Drs. Not and Thibodeau used microfossils, called foraminifer, found in a sediment core to estimate the ocean's previous temperature. Imaged, the foraminifer species used in this study

Drs. Not and Thibodeau used microfossils, called foraminifer, found in a sediment core to estimate the ocean's previous temperature. Imaged, the foraminifer species used in this study

Drs. Not and Thibodeau used microfossils, called foraminifer, found in a sediment core to estimate the ocean's previous temperature. Imaged, the foraminifer species used in this study

Many climate models predicted a weakening, or even a collapse of this branch of circulation under global warming, partly due to the release of freshwater from Greenland's ice sheet.

This freshwater has a lower density than salt water, thus preventing the formation of deep water which slows down the entire circulation.

However, this weakening is still being discussed strongly due to the lack of AMOC's long-term record.

Drs. Not and Thibodeau used microfossils, called foraminifer, found in a sediment core to estimate the ocean's previous temperature.

The sediment nucleus used is in the Laurentian Channel, on the Canadian coast, where two major streams meet.

The strength of these currents will control the temperature of the water at the core, meaning that the temperature reconstructed from this nucleus indicates the strength of the North Atlantic circulation.

With their employees from the United States, they validated their results using instrument data and two numerical models that can simulate the climate and the ocean.

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