The study found that the circulation of the Atlantic Ocean is weakest in at least 1,600 years – here’s what that means for the climate

The study found that the circulation of the Atlantic Ocean is weakest in at least 1,600 years – here’s what that means for the climate

The current system affecting the Atlantic Ocean, which plays a vital role in redistributing heat across our planet’s climate system, is moving much more slowly than it has been in at least 1,600 years. This is the conclusion of a file New study Published in Nature Geoscience by some of the world’s leading experts in the field.

Scientists believe that part of this slowdown is directly related to us Climate warming, Like Thaw It changes the balance in the northern waters. Its effect can be seen in storms, heat waves and sea level rise. It reinforces concerns that if humans are not able to limit warming, the system may eventually reach a tipping point, leading to chaos in global climate patterns.

An integral part of this system is the Gulf Stream along the eastern coast of the United States, which is known as the Atlantic Meridian Inversion Circulation, or AMOC. Best known in the 2004 moviethe day after tomorrow, “Where the ocean current suddenly stops, causing massive killer storms around the world, like a supercharged hurricane in Los Angeles and a wall of water hitting New York City.

As with many science fiction movies, the plot is based on a true concept but the effects reach a dramatic point. Fortunately, a sudden blackout is not expected anytime soon – if at all. Even if the tide eventually stops – and this is the subject of intense debate – the result will not be instant storms greater than life, but over years and decades the impacts are sure to be devastating to our planet.

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Recent research shows that blood circulation has slowed at the least 15% since 1950. In the new study, scientists say that the current weakness is “unprecedented in the past millennium.”

Since everything is connected, hysteresis is already affecting Earth’s systems, and by the end of the century it is estimated to spin It might slow down by 34% to 45% If we keep heating the planet. Scientists fear that this kind of slowdown will put us dangerously close to tipping points.

The importance of the conveyor belt for the global oceans

Because the equator receives a lot more direct sunlight than the cooler poles, the heat builds up in the tropics. In an effort to reach equilibrium, the Earth sends this heat north from the tropics and the cold south from the poles. This causes winds to blow and storms.

The The majority of From that heat the atmosphere redistributes it. But the rest is moving more slowly by the oceans in the so-called conveyor belt of the World Ocean – a global system of currents connecting the world’s oceans, moving in all different directions, horizontally and vertically.

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NOAA


Through years of scientific research, it has become clear that the Atlantic part of the belt conveyor – AMOC – is the engine that drives its operation. It moves water at a rate of 100 times the flow of the Amazon River. Here’s how it works.

A narrow strip of warm, salty tropical water near Florida, called the Gulf Stream, is transported north near the surface to the North Atlantic. When it reaches Greenland, it cools enough to be denser and heavier than the surrounding water, at which point it sinks. Then this cold water is transported south in deep water streams.

Through alternative records such as the cores of ocean sediments, which allow scientists to reconstruct a distant past that goes back millions of years, scientists know that this current has the potential to slow down and stop, and when the climate in the Northern Hemisphere does it can It changes quickly.

One important mechanism through the ages, which acts as a lever of sorts to control the velocity of AMOC, is the melting of glaciers and the flow of fresh water into the North Atlantic. This is because fresh water is less saline, and therefore less dense than sea water, and it does not sink easily. Too much fresh water means that the conveyor belt loses its submerged portion of its engine and thus loses its momentum.

This is what scientists think is happening now as arctic ice, in places like Greenland. It melts at an accelerated rate Because of man-made climate change.

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Central climate


Scientists recently noted A. Cool point, Also known as A warming pit in the North Atlantic Ocean, In a swath of the North Atlantic around southern Greenland – one of the only places on the planet that is really cool.

The fact that climate models predicted this provides more evidence that they indicate excess Greenland ice melt, more precipitation and the consequent slowdown in heat transfer northward from the tropics.

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The globe is about to warm, except for a cold spot in the North Atlantic Ocean.

NASA


In order to ascertain the extent of the recent unprecedented slowdown in AMOC, the research team compiled agent data mainly taken from archives of nature such as ocean sediments and ice core, which date back more than 1,000 years. This helped them reconstruct your mom’s flow history.

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

While each individual piece of intermediate data is not a perfect representation of AMOC evolution, the combination of the two revealed a powerful picture of cycle inversion, says lead author of the paper, Dr Lefk Kaiser, a climate physicist at the University of Maynooth in Ireland.

“The results of the study indicate that it was relatively stable until the late nineteenth century,” explains Stefan Ramstorff of the Potsdam Institute for Climate Impact Research in Germany.

The first significant change in records of ocean circulation occurred in the mid-nineteenth century, after a well-known regional cooling period called the Little Ice AgeThat spanned from the fourteenth century to the nineteenth century. During this time, low temperatures often froze rivers across Europe and destroyed crops.

“With the end of the Little Ice Age around 1850, ocean currents began to deteriorate, and a second, more severe decline followed since the mid-twentieth century,” said Ramstorf. The second decline in recent decades was likely due to global warming from burning and pollution emissions of fossil fuels.

Nine of 11 data sets used in the study showed that the weakness of AMOC in the twentieth century is statistically significant, providing evidence that the slowdown is unprecedented in the modern era.

Impact on storms, heat waves and sea level rise

Caesar says this is already echoing in the climate system on both sides of the Atlantic. “As the current slows, more water could accumulate on the east coast of the United States, causing sea levels to rise. [in places like New York and Boston]I explained.

On the other side of the Atlantic Ocean, in Europe, evidence shows that there are influences on weather patterns, such as the path of storms from the Atlantic Ocean as well as heat waves.

Specifically, the European heat wave in the summer of 2015 was linked to the record cold in the North Atlantic of that year – this paradoxical effect appears to occur because the cold North Atlantic reinforces the air pressure pattern that directs warm air from the south to Europe, she said.

According to Caesar, these effects are likely to continue to worsen as global warming continues and AMOC slows further, with more extreme weather events such as changing the course of a winter storm coming from the Atlantic and possibly more intense storms.

CBS News posed to Caesar the million-dollar question: if or when might AMOC reach a tipping point leading to a complete shutdown? She replied, “Well, the problem is we don’t yet know how many degrees of global warming will reach the tipping point in AMOC. But the more it slows down, the more likely it will happen.”

Moreover, she explained, “Tipping does not mean that this happens immediately, but because of the feedback mechanisms, the continuous slowdown cannot be stopped once the tipping point is crossed, even if we manage to bring global temperatures down again.”

Caesar believes that if we stay below 2 ° C of global warming, it is unlikely that AMOC will capsize, but if we reach 3 or 4 degrees of warming then the chances of a sudden rise. Staying below 2 ° C (3.6 ° F) is one of the goals of the Paris Agreement The United States has just joined.

If the tipping point is exceeded and the AMOC stops, the northern hemisphere will likely cool due to the significant reduction in tropical heat being pushed north. But then, Caesar says, science does not yet know exactly what will happen. “This is part of the risks.”

But humans have some leverage in all of this, and the decisions we make now regarding how quickly we move away from fossil fuels will determine the outcome.

“Whether or not we are crossing the tipping point by the end of this century depends on the amount of warming, that is, the amount of greenhouse gases emitted into the atmosphere,” explains Caesar.

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