Mid-summer North Sea survey reveals warmer waters and Atlantic inflow
After 13 days at sea, the research vessel Atair has completed 65 of the 111 planned measurement stations as part of this summer’s survey of the North Sea. The Federal Maritime and Hydrographic Agency of Germany (BSH) reports that the mission is progressing well and already delivering valuable insights into current environmental conditions.
Owned and operated by BSH, Atair entered service in 2021, replacing an earlier namesake vessel dating back to 1987. At 75 metres in length and 16.8 metres in beam, she draws five metres and cruises at a service speed of up to 13 knots. Equipped with LNG propulsion, the vessel accommodates 18 crew members and up to 15 scientists, and is fitted with a suite of scientific facilities, including laboratories, multiple sonar systems, rigging for the deployment of external instruments, and ample deck space for additional temporary equipment.
Conducted in cooperation with the Helmholtz Centre Hereon, the survey is aimed at producing a detailed assessment of the North Sea in the summer of 2025. At each station, a CTD probe is used to collect high-resolution vertical profiles of temperature, salinity, oxygen, fluorescence and turbidity. Water samples are also taken for later laboratory analysis, including dissolved inorganic carbon, alkalinity, nutrients and trace metals.
The route has taken the team from Bremerhaven along the Dutch coast and up to 58°N, passing near Aberdeen, Peterhead and the Norwegian coastline. Conditions on board have been challenging at times, with wind speeds reaching up to seven on the Beaufort scale, making restful nights rare.
Marked warming and Atlantic water inflow
Preliminary observations indicate that the North Sea is noticeably warmer than in previous years. Surface temperatures in many areas are 2–3°C higher than in 2024, with the highest measurement exceeding 21°C off southern Norway. The Norwegian Trench also appears significantly warmer, and researchers observed a distinct inflow of saltier Atlantic water along its western edge – likely the result of persistent strong winds pushing oceanic water masses into the basin.
These changes in temperature and salinity may have broader implications for water mass dynamics, stratification and biogeochemical processes. The ongoing lab analysis of collected samples will offer further insight into these patterns.
Shifting visibility and coastal conditions
As part of the daylight sampling programme – 37 stations so far – Secchi disk depths have been measured, ranging from four metres in coastal waters to 14.5 metres offshore. This variation reflects reduced underwater visibility in more turbid coastal zones. Chlorophyll and plankton samples were also taken to support ecological assessments of productivity and food web conditions.
Currently, Atair is docked in the Danish port of Thyborøn for a scheduled crew and team rotation. Once weather and sea conditions allow, the voyage will continue, with the aim of capturing a comprehensive picture of the North Sea’s summer state in 2025.
