Tens of thousands of dead fish washed up on the Gulf Coast of Texas after running out of oxygen in the warm waters, authorities say, in Freeport, Texas, U.S., June 9, 2023. DARRELL SCHOPPE/COVER IMAGES/VIA SIPA
The first lights came on in April, when surface temperatures in the North Atlantic Ocean began to rise above normal. In May, the European meteorological service Copernicus reported records, in an area stretching from Ireland to the Canary Islands, via the United Kingdom, the Bay of Biscay and the Iberian Peninsula. And then, from mid-June, a heat peak occurred, of unprecedented magnitude. On June 21, the United States Oceanic and Atmospheric Observation Agency reported that the sea surface thermometer read 23.3°C, 1.28°C higher than the average for this time of year. ‘year.
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Currently, the phenomenon is continuing, with a temperature locally 5°C to 6°C higher than what is usually observed in the west of Ireland and off England. Since the beginning of July, the sea has been at 22°C at the bottom of Brest harbour. Never seen. “There are hardly any pockets of cold in the North Atlantic. We are 0.8 °C above the previous record of 1995, and there is a big risk that it will last. Because of its inertia, the ocean will remain in a warm atmosphere all summer long”considers Thibault Guinaldo, oceanographer at the Center for Space Weather Studies of Météo-France and CNRS.
According to Raphaël Seguin, marine ecologist at the University of Montpellier, this heat wave will actually last until September. “The situation is mixed in the North Atlantic but, overall, 40% of the ocean is in a marine heatwave situation and, by the end of the summer, it is expected to be 50% »he said.
Over the weeks, the probable causes of this overheating became clearer. “The backdrop is global warming”, explains Mr. Guinaldo. As shown by a study by the National Center for Meteorological Research published in May, with the aim of learning from a particularly hot summer 2022 on the surface of the sea, weather phenomena can accentuate the general trend. In question, this time, the persistent anticyclones on the British Isles.
“Large masses of air descend from high altitudes and dry out strongly, preventing the formation of clouds. In regions where there are usually quite a few, the result is a surplus of energy, the clouds no longer being there to reflect the solar radiation. There is also less wind, and therefore less mixing of the waters in the sea »describes Mr. Guinaldo.
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2023-07-15 10:40:14
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