Objectives and scientific background 
The objective of the BSH North Sea Summer Surveys (NSSS) is to monitor the oceanographic 
and chemical state of the North Sea at the time of expected maximum Sstratification and 
ohytoplankton productivity having passed its peak. 
All parameters exhibit a strong seasonal and/or inter-annual variability. Seasonal heating leads 
to the establishment of a seasonal thermocline between spring and end of August or midst of 
September. 
The data provide the basis for the calculation of heat and salt budgets, and the identification 
af long-term changes, possibly due to climate change. 
They are also used for the validation of operational and climate models and for the calibration 
of satellite-based ocean colour data and downstream products (Secchi depth, turbidity, CDOM, 
chlorophyll-a) which are used for assessments and MSFD reporting. 
The BSH North Sea Summer Surveys started in 1998 (see Table 1) and were conducted 
yearly. They cover the entire North Sea with seven zonal coast to coast sections between 54° 
and 60°N and additional stations between 54°N and the entrance of the English Channel. As 
to monitor artificial radio nuclides more stations in the English Channel respectively in the 
Skagerrak are served alternately every second year. Unfortunately, in 2021 the radioactivity, 
nutrient and environmental pollution working groups were not able to take part in the survey. 
In 2021, as for many other years, the work was expanded to the Northwest to additionally 
monitor the inflow of Atlantic Water. 
Most of the data are available via the German Oceanographic Data Centre (DOD), selected 
surface data (5 m) are also fed into the MERis MAtchup In-situ Database (MERMAID).1 
ı http://www.bsh.de/en/Marine_data/Observations/DOD_Data_Centre/index.jsp 
attp:/hermes.acri.fr/mermaid/home/home.php 
2