Sea surface water temperature is approaching its annual maximum.
Although the days have been gradually getting shorter since June 21, the sea surface temperature is still rising. Because the upper water layers warm up very slowly and will continue to be heated in the coming weeks by the summer sun, which is still high.
The oceans are huge heat stores, because on the one hand the water has a very high heat capacity, ie it requires a lot of energy to increase its temperature, and on the other hand there is a huge amount of water in the world’s oceans. The seasonal temperature fluctuations are only limited to the top 50 to 100 meters, the so-called mixed layer. The temperature distribution of the deep sea remains almost unchanged. As a result, the seas react very sluggishly to seasonal changes in solar radiation and lag behind the position of the sun by around 6 to 8 weeks.
At 24.8 degrees, the sea surface temperature in the entire North Atlantic is currently around 1.5 degrees above the long-term average and only 0.1 degrees below the previous record value from September 2022. This deviation will increase further by late summer. This is extreme and unprecedented warming.
The temperatures on the North and Baltic Seas are currently 18 to 20 degrees, suitable for swimming. In the next few weeks, the water near the coast will warm up by 3 to 5 degrees. In the Bay of Biscay you can already refresh yourself in the 20 to 23 degree cool water. At 17 to 20 degrees, the water off the Portuguese coast is sometimes even colder than on the North Sea coast.
Water temperatures on 24.7.2023
If that’s too cold for you, you should turn to the Mediterranean Sea, which is often referred to as the world’s largest bathtub for good reason. Because here the water temperatures range from around 24 degrees off the French coast to 30 degrees on the southern Spanish coast. On the Balearic Islands, the values are around 28 degrees and thus about 3 degrees above the long-term average. The water temperature in the central Mediterranean is also significantly higher than normal at 27 to 30 degrees. Even in the northern Adriatic you only cool down moderately at 27 to 28 degrees. 29 degrees are reported before Bari, about 5 degrees above the typical value for the time of year. In the eastern Mediterranean, the water temperatures are around 1 to 3 degrees above average at 25 degrees in Santorini and 29 degrees in Antalya.