There is a region of the North Atlantic that for years intrigue to experts in weather and oceanography. They call her the “cold stain” of the Atlantic and is a small oasis in an ocean whose waters have been tempered over the years. In a matter of weeks, two studies bring us closer to the resolution of this enigma.
Two studies. The two new research published in recent weeks, one in the magazine Communications Earth & Environment And the other in Sciences Advances They address the enigmatic stain and give differentiated but complicitary explanations of the oceanographic dynamics behind this cold spot on the surface of the sea. One of the central axes for both studies is the circulation of southern overturning of the Atlantic (AMOC), one of the most important maritime currents for the climate on both sides of the “puddle.”
A cold stain. The cold stain of the Atlantic is a relatively small region of the ocean surface whose average temperature has dropped (about 0.3º Celsius) instead of ascending as has happened with most surface waters. La Mancha is located south of Greenland, not far from the coasts of Newfoundland, near the waters of the Arctic Ocean.
AMOC. Both works indicated directly to the AMOC current as the centerpiece of this climate puzzle. But what is exactly AMOC? The southern overturn circulation of the Atlantic is a current connected to the thermhaline circulation that transports water from north to south and from south to north in the Atlantic Ocean.
The North Atlantic the current transports through the surface layers of the ocean the warm waters of tropical latitudes towards high latitudes and the border with the Arctic. Arrival to these latitudes, the water cools and descends to the deepest layers of the ocean, where it is dragged into a current back towards the South Atlantic.
This current not only transports water masses of different temperature but also of different salinity: the water of the tropics is warmer more salty than the water in the Arctic environment.
A weakened current. The first of the studies focused on the weakening of this current observed in recent years. In its analysis, the team used direct observations of the current in the last two decades with indirect measures taken throughout the last century in order to “rebuild” the changes in this circulation.
They contrasted these data with the predictions that different oceanographic models generated under different assumptions. According to its analysis, only a weakened AMOC current could be linked to the data corresponding to compiled observations.
“It is a very robust correlation,” Yuan Li, co -author of the study, explained in a press release. “If you look at the observations and compare them with all simulations, only a monoc-debilitated scenario reproduces the cooling in this unique region.”
By sea and by air. The second study indicated, however, the weakening of the AMOC current may not be the only relevant factor in the appearance of the Atlantic cold stain. According to this study, the weakening would have been the initial trigger, but the cooling of the stain would have in turn reduced evaporation and humidity in the atmosphere of the region.
Since water vapor is a greenhouse gas, this would have been in turn in the reduction of this effect and therefore a regional cooling. “Reducing the greenhouse effect, so to speak, will feed back the surface and amplify the existing cold anomaly,” said Yifei Fan, co -author of this second study.
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