The rate of ocean warming has almost doubled since 2005, according to a report from the European Copernicus observatory, published on Monday, September 30. The study also reports that more than a fifth of the world’s ocean surface experienced a severe heat wave in 2023.
“Ocean warming can be considered our sentinel of global warming. It has been increasing steadily since the 1960s, and since 2005 the rate of ocean warming has roughly doubled.stressed oceanographer Karina von Schuckmann during a video conference in which she presented the eighth Copernicus state of the oceans report. The oceans are warming at 1.05 watts per square meter (W/m2) since 2005, compared to 0.58 W/m2 in previous decades, according to the report.
This work consolidates the IPCC reports. In 2019, these UN-appointed climate experts estimated ” likely “ that the rate of warming of the oceans has “More than double since 1993”.
Hurricanes, storms, sea heat waves
This warming can be explained by the fact that the oceans have absorbed since 1970 “more than 90% of the excess heat in the climate system” caused by humanity’s massive emissions of greenhouse gases, according to the IPCC. The oceans, which cover 70% of the Earth’s surface, are an important regulator of the Earth’s climate. Warmer waters bring more violent hurricanes and storms, with resulting destruction and flooding.
This warming is also accompanied by an increase in marine heat waves. Thus, 22% of the world’s oceans experienced at least one severe or extreme heat wave in 2023. More widespread, marine heat waves also tend to lengthen, with an average maximum annual duration that has doubled since 2008, passing from twenty to forty days. .
In the northeast of the Barents Sea, “The seabed appears to have entered a state of permanent marine heat wave”according to a study cited by Mme Schuckman.
Mass mortality of species.
In August 2022, a record temperature of 29.2°C was recorded in the coastal waters of the Balearic Islands, “The highest regional water surface temperature in forty years”the report also states. The same year, a marine heat wave in the Mediterranean Sea penetrated about 1,500 meters below the surface, illustrating how heat can spread throughout the water column.
Episodes of marine heat waves can cause migrations and episodes of mass mortality of species, degrade ecosystems, but also reduce the ability of ocean layers to mix between the bottom and the surface, thus hindering the distribution of nutrients. they can too “have implications for fishing productivity”impacting fishing, underline Mme Schuckman.
The report also notes that the acidity of the oceans, which absorb a quarter of the CO₂ emitted by human activities, has increased by 30% since 1985. Above a certain threshold, the acidity of seawater becomes corrosive to skeletons. and the shells of corals, mussels, oysters, etc.
This threshold, considered as a “planetary limit”must be crossed “in the near future”according to a report published last week by the Potsdam Institute for Climate Impact Research (PIK).
