Heat wave in the North Atlantic Ocean

Tens of thousands of dead fish washed up on the Texas Gulf Coast after they ran out of oxygen in warm waters, according to officials, in Freeport, Texas, on June 9, 2023. DARRELL SCHOPPE/COVER IMAGESCOVE / DARRELL SCHOPPE/COVER IMAGES/SIP

The first warning bells sounded in April, when temperatures at the surface of the North Atlantic Ocean began to rise above normal. In May, the European meteorological service Copernicus reported record highs in an area stretching from Ireland to the Canary Islands, via the UK, the Bay of Biscay and the Iberian Peninsula. And then, from mid-June onwards, a heat spike occurred on an unprecedented scale. On June 21, the US National Oceanic and Atmospheric Administration reported that the thermometer at the water's surface stood at 23.3°C, or 1.28°C above the average for this time of year.

The phenomenon is currently ongoing, with temperatures locally 5°C to 6°C higher than usual to the west of Ireland and off the coast of England. Since the beginning of July, the sea temperature has reached 22°C in the Brest harbor, for the first time ever. "There are virtually no more cold pockets in the North Atlantic. We're 0.8°C above the previous record set in 1995, and there's a big risk that this will continue. Because of its inertia, the ocean will remain warm all summer," said Thibault Guinaldo, an oceanographer at Météo-France and the CNRS's Centre d'Etudes en Météorologie Spatiale (Center for the Study of Spatial Meteorology).