2023-11-23 07:30:59
In a study published in Science, scientists demonstrate that currents of warmer water coming from the North Atlantic and moving towards the Arctic are linked to the Arctic dipole. This term corresponds to an atmospheric circulation pattern which causes different directions of wind circulation and which acts on the melting of the sea ice.
For decades, the Arctic Ocean has been warming faster than the average ocean temperature in the rest of the world. This situation is partly explained by the “Atlantification” of the Arctic, that is to say by currents of warmer and relatively salty water coming from the North Atlantic which move towards the Arctic. The process implemented is complex and involves interactions between the atmosphere-ocean system, but its origin was until now poorly understood. In a study published in the journal Scienceresearchers including those from the University of Alaska in Fairbanks, reveal that this phenomenon is linked to a meteorological factor called the Arctic dipole.
First brought to light in the mid-1990s, the Arctic dipole refers to an atmospheric circulation pattern which is characterized by differences in atmospheric pressure between several regions of the northern hemisphere. It produces a wind pattern that generates upper ocean currents that have year-round effects on regional air temperature, atmosphere-ice-ocean heat exchange, ice drift, and biological consequences. The authors of this study identified that the directions of wind circulation have the effect of limiting or encouraging the movement of warmer water currents towards the Arctic.
According to them, the Arctic dipole currently at work takes place according to a pattern described as positive. It is characterized by high pressures over the Canadian part of the Arctic and creates clockwise winds. At the same time, a low pressure system is centered over the Siberian Arctic, with winds circulating counterclockwise. This pattern causes a decrease in flow from the Atlantic Ocean to the Arctic Ocean via the Fram Strait east of Greenland, as well as an increase in Atlantic flow in the Barents Sea, located north of Norway and in the west of Russia. Ultimately, this configuration has a positive effect and helps slow down the flow of warmer water towards the Arctic and therefore limit the melting of the sea ice.
The Arctic Dipole might once more have a negative impact soon
Through the analysis of a wealth of data, including direct instrumental observations, reanalysis products and satellite information going back several decades, scientists were able to demonstrate that the Arctic dipole alternates in a cycle of approximately 15 years and that the current cycle started in 2007. Since then and until 2021, it has therefore contributed to reducing the decline of Arctic sea ice compared to the previous period from 1992 to 2006. In recent years, It appears that the thickness of the surface layer of cold Arctic Ocean water has increased, making it too thick and too stable to mix with the warmer, saltier water flowing below and from the surface. ‘Atlantic. This layer of cold, less dense water currently prevents warmer seawater from melting the ice.
But according to the researchers, the current cycle is most likely approaching its end and they estimate that the Arctic dipole might go into negative mode soon and therefore have the effect of participating in the acceleration of the melting of the ice. “We have passed the peak of the currently positive Arctic dipole regime, and it might reverse at any time,” says Igor Polyakov, the lead author of this study. This might have significant climatological implications, including potentially more rapid loss of sea ice in Arctic and subarctic climate systems. »
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