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Atlantic Ocean circulation is the weakest in at least 1,600 years, study finds – here's what that means for the climate - CBS News
Feb 26, 2021 2 mins, 22 secs

An influential current system in the Atlantic Ocean, which plays a vital role in redistributing heat throughout our planet's climate system, is now moving more slowly than it has in at least 1,600 years.

Scientists believe that part of this slowing is directly related to our warming climate, as melting ice alters the balance in northern waters.

And it bolsters concerns that if humans are not able to limit warming, the system could eventually reach a tipping point, throwing global climate patterns into disarray.

But the rest is more slowly moved by the oceans in what is called the Global Ocean Conveyor Belt — a worldwide system of currents connecting the world's oceans, moving in all different directions horizontally and vertically. .

A narrow band of warm, salty water in the tropics near Florida, called the Gulf Stream, is carried northward near the surface into the North Atlantic.

One important mechanism through the ages, which acts as a lever of sorts controlling the speed of the AMOC, is the melting of glacial ice and resulting influx of fresh water into the North Atlantic.

Recently scientists have noticed a cold blob, also known as the North Atlantic warming hole, in a patch of the North Atlantic around southern Greenland — one of the only places that's actually cooling on the planet.

The team used a combination of three different types of data to obtain information about the history of the ocean currents: temperature patterns in the Atlantic Ocean, subsurface water mass properties, and deep-sea sediment grain sizes, dating back 1,600 years. .

"Specifically, the European heat wave of summer 2015 has been linked to the record cold in the northern Atlantic in that year — this seemingly paradoxical effect occurs because a cold northern Atlantic promotes an air pressure pattern that funnels warm air from the south into Europe," she said

CBS News asked Caesar the million-dollar question: If or when the AMOC may reach a tipping point leading to a complete shutdown

She replied: "Well, the problem is that we don't know yet at how many degrees of global warming to hit the tipping point of the AMOC

Moreover, she explained, "Tipping does not mean that this happens instantaneously but rather that due to feedback mechanisms the continued slow down cannot be stopped once the tipping point has been crossed, even if we managed to reduce global temperatures again."

Caesar believes if we stay below 2 degrees Celsius of global warming it seems unlikely that the AMOC would tip, but if we hit 3 or 4 degrees of warming the chances for the tipping rise

If the tipping point is crossed and the AMOC halts, it is likely the Northern Hemisphere would cool due to a significant decrease in tropical heat being pushed northward

"Whether or not we cross the tipping point by the end this century depends on the amount of warming, i.e

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