Water temperatures in the North and Baltic seas hit record highs in spring 2025
Clean Energy Wire
Water temperatures in the North Sea this spring hit their highest level ever recorded by Germany’s Federal Maritime and Hydrographic Agency (BSH). The average temperature of 8.7°C topped the long-term average by 0.9°C. “The whole North Sea is experiencing the warmest spring since the beginning of analyses in 1997," said the BSH, adding that temperatures in the Baltic Sea had also hit record levels in early 2025. The BSH said the high average temperatures are “another sign of ongoing climate change”, pointing out that extreme heat waves can also occur as a marine phenomenon.
In waters of the northern German city of Kiel on the Baltic Sea, a heatwave which saw the near-surface water temperature hit the top-ten percent of the past 30 years lasted for a record 55 days, from 28 March to 21 May, the agency added. “The temperatures during the heatwave were 2.6°C above the 1991-2020 average, with a peak of 4.3°C above average,” said BSH climate scientist Claudia Hinrichs.
Temperature variations differed locally, the agency added. The greatest divergences occurred in the eastern North Sea, off the coasts of Norway and Denmark, where temperatures were about 2°C above the long-term average. In Germany’s territorial waters, temperatures were 1.5°C degrees higher. In the Baltic Sea, the northern portion near Sweden and Finland was colder than the long-term average, while the south-western portion around Germany and Denmark was 2°C warmer.
