University of São Paulo: Atlantic ocean current is more resistant to polar melt than previously thought

In a study published last week in the journal Nature Climate Change , scientists at the University of Wisconsin-Madison, in the United States, revealed that the ocean current known as the Meridional Upturn Circulation, or AMOC, would be less affected by the melting of the oceans. ice caps in the Northern Hemisphere than previously thought.

According to professor Ilana Wainer, from the Oceanographic Institute at USP, the conclusion of the new study is positive for the planet. “The Southern Circulation is the contribution of the oceans to redistribute the excess heat that we receive in the tropics due to the sun and the heat deficit that exists in the polar regions”, explains the professor.

Prior to the new finding, most simulations of our future climate assumed that AMOC could be quite sensitive to melting Arctic ice, which would cause abrupt changes in ocean circulation.

For Ilana, who has already worked with models used by the authors of the article, the result is “spectacular”. “He was a pioneer trying to prescribe these melt flows since the last glacial maximum, and he was very successful,” he opines.

melting of the hubcaps
Broadly speaking, the Atlantic Ocean current acts as a conveyor belt that moves warm tropical surface waters to the north and cooler, deeper waters to the south. It is one of the keys used to predict future climate disasters, especially when it comes to global warming and the melting of ice caps.

However, building on previous work, researchers are revising their understanding of the relationship between AMOC and freshwater from melting polar ice.

Injecting freshwater from the possible polar melt would likely “change the density of the ocean, as freshwater is less dense. Then you stratify it and form the deep water that is what makes up AMOC. It goes to smaller depths and with less intensity, so you wouldn’t be able to do this heat transfer in such a vigorous and efficient way”, he explains.

In the paper, the researchers described a new simulation model that matches the heat of the last 10,000 years. And they did so by eliminating the trigger that most scientists believe would cripple AMOC.

“This study is showing that the consequences would not be that catastrophic”, stresses the expert, revealing that, in the new model, although the climate record shows an abundance of fresh water that came from the final melting of the ice sheets in North America and in Europe, AMOC has barely changed. And this is particularly important for climate models that assess how AMOC will respond to future increases in freshwater from melting ice.

Although the current is more resilient than previously thought, the professor warns that extreme weather events are already a reality and require attention: “We are already in an almost irreversible scenario of global warming, sea level rise and extreme events . We have to stop emitting greenhouse gases and stop using an energy matrix based on fossil fuels. The consequences are numerous not only for AMOC, but for biodiversity and ecosystems”, concludes the professor.

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