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The Atlantic Ocean has been warming the Arctic for at least 100 years |  Science

The Atlantic Ocean has been warming the Arctic for at least 100 years | Science

Since the beginning of the twentieth century, the Atlantic Ocean has increasingly penetrated into the Arctic. Coming from the south and without the ice counterweight, the waters of the Atlantic Ocean are much warmer and saltier. This means that the frozen masses of the sea are accelerating the melting of the ice, reducing its extension further and further. This process joins the already known effect of global warming. Between the two phenomena, the Arctic is warming at twice the rate of the rest of the world’s oceans.

Climate scientists have known that the Arctic has been warming more than other oceans for at least four decades. This thermal amplification appears to be related to the melting itself. In short, due to climate change, the annual progression of ice in the cold months was decreasing while the retreat of permafrost in the warm months was increasing and accelerating. The result was less ice and less time. Like a mirror, this ice sheet reflects much of the solar radiation now trapped in the very dark water. Hence the additional warming of the region and all its regional and global environmental consequences. But that is only half the story.

In 2017, the magazine Science published Russian-American investigation which showed how the Barents Sea (which submerges most of northern Siberia) had changed its structure since the turn of the century. Arctic seas, due to lower temperature and lower salinity (due to freshwater contribution from melt) are very constant and stratified, and there is no vertical circulation. In the rest of the planet, seawater is like the air in the atmosphere: differences in temperature (and salinity) fuel currents. In the air it is called atmospheric circulation and is the main protagonist of weather changes. In water, it is called thermo-brine circulation and is what moves the water on a large scale. The North Pole was almost bizarre. But that study Science He showed that Arctic waters, pushed up by the warmer and saltier waters of the Atlantic Ocean, were moving. This phenomenon was baptized as Atlanteification. Now, another work, published in science progress, point to this Atlanteification The North Pole is not from now, it has been in the making for at least a century.

“In 800 years, we have noticed that our records seem to be fairly consistent. But suddenly, at the beginning of the twentieth century, it happened [un] Noticeable change in temperature and salinity

Tessie Tommaso, from the Polar Sciences Institute of the National Research Council, Italy

An international group of researchers has reconstructed the past 800 years of temperature and salt in the Arctic Ocean. They did it precisely at one of their entrance gates: the Fram Strait, which connects the North Pole and the Atlantic Ocean, leaving the islands of Svalbard to the east and the northern coast of Greenland to the west. To find out how warm and salty water was in the past, they relied on a series of very ingenious signs: a series of microorganisms (algae, archaea and protists) that settled and transformed over time. Each of these tiny organisms behaves differently depending on how cold, hot, or salty the water is. They dug up the seabed and glaciers and took nearly annual samples of these creatures.

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In general, they noted significant stability throughout the study period. However, between 1896 and 1917, they discovered changes in all the microorganisms analyzed. In a group of archaea, sensitive to sea surface temperature, they observed changes in the cell membrane. Other organisms, some foraminifera that live on the sea floor, pick up a sudden increase in the salinity of the water around the same time. Two other Archaea, which accounted for 50% of all records in the last 800 years, almost disappeared, reaching only 2% in the first half of the 20th century. Everything indicates that the North Pole is not what it used to be.

Researcher Tissi Tommaso, of the Polar Sciences Institute of the Italian National Research Council and co-author of the study highlights the shift: “In the entire 800-year period, we notice that our temperature and salinity records appear to be quite constant. But suddenly, at the beginning of the 20th century, this change occurred. Notable for its temperature and salinity, which is quite remarkable.”

To ask why this happened Atlanteification At the North Pole, Tommaso answered that it is a difficult question to answer. They have a possible explanation, however, as they lack evidence beyond circumstantial: “We don’t have a model to support our hypothesis, but we did detect a strong association with sub-polarity dynamics,” he says in an email. It refers to the play of the great currents of the North Atlantic, particularly the remnants of the Gulf Stream rising from the tropical seas and the sub-polar circulation, a circular movement of waters south of Greenland and east of the Labrador Peninsula. It is these waters, along with the waters of the Barents and the Greenland Sea, that complete the circuit initiated by the rising current of the Gulf. “Specifically, we believe that the gradual deterioration in convection [movimiento vertical por diferencias de temperatura] In Labrador, it lets more heat in the oceanic mass move north,” Tommaso adds.

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Weak ocean circulation has already been detected, however, it was supposed to be a matter of decades past. Climate scientist and co-leader of the Barcelona Supercomputing Center’s Climate Prediction Group, Pablo Ortega, is one of those who recently investigated these oceanic changes. “When we talk about past and future changes in ocean circulation, we tend to focus primarily on weakening it, but for certain aspects, such as Atlanteification, the redistribution of currents associated with it is more important,” he says. He elaborates: “In the North Atlantic, for example, we have the Gulf Stream which transports warm, salty waters from the Caribbean Sea to near the Atlantic coast of the Iberian Peninsula, where it branches off and part continuous toward North Sea. From where you reach the North Pole. The Gulf Stream competes with the subpolar gyroscopic rotation, which is a horizontal counterclockwise rotation that occurs in the high latitudes of the North Atlantic, and is particularly strong near the Labrador Sea region. When the latter weakens or contracts, the Gulf Stream can gain land and reach higher latitudes, increasing its influence in the Arctic.”

So the warming accelerated by the melting process joins the Atlanteification. Tommaso states that “the last amplification [térmica del Ártico] It is the result of the loss of the cryosphere that can reflect energy and sea ice, snow and glaciers.” What happened is that humans, “essentially accelerated Atlanteification It is natural to appear in this research.” For Ortega, studies are accumulating that also point to human actions as a factor in weakening the circulation of the Atlantic, “which will happen in response to global warming, and that this weakening [estaría] cause a new redistribution of the existing system.”

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