Sea surface temperatures broke a record in April and have since remained at high levels.
The ocean is overheating. According to data from the American observatory NOAA, the temperature at the surface of the seas broke a record for the month of April and has since remained at unprecedented levels. This phenomenon, alarming but not surprising for scientists, above all illustrates how human activities have transformed the oceans into a “time bomb” of global warming.
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At the beginning of April, the average temperature at the surface of the oceans, with the exception of polar waters, reached 21.1°C, beating the previous record of 21°C in March 2016. If the average started to come down a little April – a natural cycle at the end of the austral winter – temperatures have remained above seasonal records for six weeks.
“Underwater fires” that devastate algae
How to explain such a record? The world’s oceans have experienced three consecutive years of La Niña, a cyclical climatic phenomenon that cools surface waters. However, the opposite phenomenon, El Niño, seems to set in in 2023 and the transition, with the end of the cooling effect of La Niña, could have combined with long-term warming to produce this new record.
Immediately, this “is reflected at the regional level by a multitude of marine heat waves” Who “act like underwater fires, which can irreversibly degrade thousands of square kilometers of underwater forests, for example kelps, posidonia meadows or corals”describes CNRS oceanologist Jean-Baptiste Sallée. “It is not surprising that the oceans are warming, we observe it year after year at an absolutely staggering rate”recalls however this author of the Giec joined by AFP, because “the ocean, like a sponge, absorbs more than 90% of the increase in heat caused by human activities”.
The effects are not limited to marine biodiversity. “There will be increased evaporation and a high risk of more intense cyclones”, explains oceanologist Catherine Jeandel to AFP. warmer waters “function as a barrier that slows gas exchange”adds the geochemist: “The oxygen pump of the ocean will work less well” And “so will the CO2 pump”. This risks accelerating warming, because it reduces the ocean’s absorption of greenhouse gases produced by our consumption of coal, oil and gas. “By heating it, the ocean becomes a bit like a time bomb”summarizes Catherine Jeandel.