September 26, 2021

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Atlantic ocean currents show signs of decline

Posted on 08/06/2021 06:00

(Credit: Jonathan Knoxstrand / AFP – 15/8/19)

The main circulatory system of the Atlantic Ocean and an important regulator of the world’s climate In the last century almost all lost stability and may have reached an important threshold, Not reversed. A study published yesterday in the journal Nature Communications noted that the North Atlantic reverse circulation (AMOC) participating in the Gulf Stream is on the verge of collapse due to global warming. The authors warn that, among other impacts, this phenomenon could “significantly cool Europe”, in addition to having a severe impact on tropical monsoon systems.

The Amog is a movement of hot water carried by tropical regions of the Atlantic to the north by the Gulf Stream, which warms Western Europe. When they reach the northern part of the ocean, the water cools, becomes denser and heavier, sinks to warmer levels before returning south, and the cycle begins again. “It’s one of the planet’s major rotation systems,” said Nicholas Boers, one of the authors of the study and a researcher at the Postmodern Climate Impact in Germany.

In 2018, two surveys released by the Nature Group warned Atlantic current system It is weakened by the melting of sea ice, glaciers and glaciers, releasing less dense freshwater than salt in the North Atlantic. According to David Thornelli, a researcher at the University College London and a co – author of the study, “Fresh water weakens the aquifer because it prevents it from becoming too dense to submerge.”

Most recently, four months ago, research published in Nature Geosciences and based on computer simulations with data from the Earth’s past, called the Paleoglymatic Proxy Records, showed that the current was weak for 1,600 years. Boers notes, however, that the question remains whether the weakening is related to a change in rotation or to a real loss of dynamic stability.

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Says Nicholas Boers, “The loss of dynamic stability indicates that AMOC is approaching its critical threshold, and beyond that a significant and practical, irreversible change to the current weak system is possible.”

Although the complexity of the system and the uncertainty about future levels of global warming make it difficult to know when this will happen – it could be decades or even centuries – Boers point out that the impact of this event should be avoided at all costs. “We need to immediately align our models with the observational evidence provided to assess how important or very close the amok really is,” he says.

Fingerprints

Although there is no long-term observational data on the strength of the amoeba, the ocean surface of the Atlantic Ocean has a rotational system called fingerprints in the form of temperature and salinity. “A detailed analysis of these fingerprints in eight independent codes, with records from 150 years ago, suggests that the weakening of the amok in the last century may have been associated with a loss of stability,” Boers says. “The results support the assessment that the decline of the amok is not a fluctuation or linear response to rising temperatures, but indicates an approach of a critical range in which the circulatory system may collapse.”

“Amok has a profound impact on the global climate. Therefore, continued weakening of the cycle is important new evidence to explain future regional and global climate forecasts,” said Andrew Meijers, a polar ocean researcher with the British Antarctic Survey Climate Project in the UK. “Furthermore, it is often designed as an infiltration point below some rotational force, which causes the relatively stable rotation to be unstable or collapsing.

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Many factors are associated with this phenomenon, and they are all related to global warming, such as the melting of glaciers and the formation of freshwater in the ocean. “I did not expect the excess freshwater added in the last century to ever generate such a response in the cyclone,” says Boers, who was surprised and frightened by the results of the study. According to the researcher, although it is not known what CO2 emissions levels The only thing to do is to keep the emission as low as possible, which can trigger a system crash.

Intense rain

The recently recorded rainfall in the Northeastern United States is part of a broader trend. From Maine to Virginia, there has been a sharp increase in rainfall over the region – about 2 mm of water per day depending on location since 1996 as a result of heavy rain and snow, which coincided with sea surface warming in the North Atlantic.

Heavy rainfall in the Northeast is usually caused by tropical cyclones, hurricanes at the tip and tropical cyclones. But a study published in the journal Weather and Climate Extremes found that the increase in precipitation after 1996 was due to human activity from greenhouse gases and variations in the surface temperature of the North Atlantic Ocean.

“Our previous work shows that intense rainfall in the Northeast has increased dramatically over the past 25 years, but this study is the first to demonstrate that anthropology is caused by climate change,” says lead author Juanping Huang, a researcher with the National Laboratory of Climate and Environmental Sciences.

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The study is based on previous works by Huang and co-authors, who have found that the North American northeast has received 53% more intense rainfall since 1996 and more rainfall by tropical cyclones. This group combines events with a warmer climate, which increases the amount of water that can be contained, and the less cold Atlantic Ocean, which produces stronger and more frequent hurricanes. “Our results demonstrate that multidisciplinary variation in the surface temperature of the Atlantic Ocean, the main warming factor of the Atlantic, anthropological greenhouse gases and aerosols contributed to the increase in intense rainfall in the Northeast after 1996,” says Huang.