Researchers have discovered that water in the North Atlantic has "drastically weakened". The study shows that the levels are lowest…
Researchers have discovered that water in the North Atlantic has “drastically weakened”.
The study shows that the levels are lowest in 1500 years – and climate change is required.
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.
Ocean currents play a decisive role in regulating the planet.
Longer circulation in the North Atlantic can bring profound changes in both the North American and European climate, but also in Dutch and Asian summer rainforests.
This transmission 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 effects on ocean temperatures, hydrological cycles, 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.
Research, led by Drs. Christelle Not and Benoit Thibodeau from the Department of Geosciences and the Swire Institute for Marine Sciences, Hong Kong University, are interpreted as a direct consequence of the global warming and associated melting of Greenland ice.
Slow circulation in the North Atlantic can lead to profound changes in both the North American and European climate, but also on the African and Asian summer rainforests.
& # 39; AMOC plays a crucial role in regulating the global climate, but researchers are struggling to find reliable indicators of its intensity in the past.
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, “says Dr. Thibodeau.
The research group also found a weak signal during a period called the Little Ice Age (a cold spell observed between about 1600 and 1850 AD).
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 coldest phase of the Little Ice Age there are signs that average winter temperatures in Europe and North America was 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 London Museum  The winters were bitterly cold and the summers were often cool and wet.
These conditions led to extensive crops, famine and population decline.
There were increased levels of social concern as large sections of the population were reduced to starvation and poverty.
Although it is 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 towards Europe which contributes to the cold temperature of this period.
But more work is needed to validate this hypothesis.
“While we could base the truth on our 20th 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
The find has recently been published in the prestigious journal Geophysical Research Letters.
The Atlantic Meridian Overturning Circulation (AMOC) is the branch of the North Atlantic circulation that brings warm surface water to the Arctic and cold deep water towards the equator.
This transmission of heat and energy not only directly affects the climate across Europe and North America but may affect the monsoon system of Africa and Asia through its effect on ocean temperatures, hydrological cycles, 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. The picture, the foraminifers specific 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 saltwater, thus preventing the formation of deep water and slowing down the entire circulation.
But this weakening is still heavily discussed due to the scarcity 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 is used in the Laurentian Channel, on the Canadian coast, where two important streams meet.  The string of these streams will control the temperature of the water at the core point, which means 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.