On August 22, seawater temperature (between 60 degrees south and 60 degrees north latitude) reached its highest level ever – 21.10°C, the highest sea surface temperature ever measured.
The European Earth observation service Copernicus announced this in a press release on Monday. The new figures even break the previous record of 21.09°C set in March 2024.
The timing of the new record is remarkable. Typically, seawater temperatures reach their peak in March or April, following the Southern Hemisphere summer. However, the new record comes as no surprise. Over the past few months, (near-)record sea temperatures have been consistently recorded.
Extreme consequences
The sea acts as a massive heat buffer. Water warms up much more slowly than land, but it also cools down much more slowly. As a result, heat from a long, sunny summer can accumulate in the water’s upper layer for weeks.
The combination of global warming, abundant sunshine, high-pressure systems, and light winds has caused the sea to warm up exceptionally strongly.
Warmer seawater has consequences for both humans and nature. For instance, warmer water raises sea level because it expands as it warms. Marine heatwaves damage important ecosystems, such as coral reefs, potentially putting the entire food chain at risk. In addition, warm seawater also fuels extreme weather phenomena.
A warmer ocean adds more heat and water vapor to the atmosphere, allowing for heavier rainfall and more intense storms. Warmer oceans can also store less CO2. Around Europe, the record-high sea surface temperatures along the Atlantic and western Mediterranean were associated with widespread strong or severe marine heatwaves, affecting coastal communities and ecosystems.
Belgian coastal waters
In Belgium, scientists discovered that biodiversity in the Belgian coastal waters has changed fundamentally over the past few decades due to global warming. Typical cold-water species, such as brown shrimp, gobies, and herring/sprat, are now far less abundant, whereas warm-water species (like the venomous lesser weever) and comb jellies are thriving.
Cold-water species, in particular, have taken a heavy hit. For instance, the grey shrimp population has declined by at least 78 percent. Sea bass and plaice remain stable for the time being, while other species are showing a marked increase.
Hottest June-July period on record
At the beginning of August, we already reported that Western Europe experienced its hottest June-July period on record. July saw the third and fourth heatwaves since May, marking an exceptional run of extreme heat this summer.
The average temperature for June-July for Western Europe was the highest on record, at 21.62°C, or 2.79°C above average, surpassing the previous record from 2022 and reflecting the exceptional persistence of heat since the beginning of summer.
