Scientific Background 
BSH started in 1999 a time series on mapping the annual maximum heat content and the 
annual maximum depth of the summer thermocline of the Greater North Sea (Fig. 1). The 
aims of the time series are to map the influence of climate on the oceanographic structure of 
the North Sea, to identify the inputs from the Northeast Atlantic and the Baltic Sea, and to 
assess its consequences for the North Sea ecosystems. 
The North Sea is a marginal sea of the Atlantic Ocean situated on the Northwest European 
Shelf and is connected to the open ocean via the northern margin and, to a minor degree via 
the English Channel. As a consequence, the southern North Sea is largely influenced by the 
rather warm water of the temperate part of the NE Atlantic. The northern North Sea receives 
cooler waters from the north western part of the NE Atlantic and from the Norwegian Sea. 
The Dogger-Fisher-Bank complex and the wedge-shaped general bathymetry of the Greater 
North Sea prevent largely the spreading of cool deep water into the Southern North Sea. 
Therefore, the shallow southern North Sea is very susceptible to physical changes in the 
temperate Northeast Atlantic and to local atmospheric influences. In the northern North Sea 
the influence of the local atmosphere on the water body is mainly limited to the uppermost 
10" of metres. The underlying water derives its thermal conditions largely from the open 
3cean. 
Temperatures of the different water masses, including derived parameters like heat content 
and the depth of the thermocline during the time of the maximum heat content are suitable 
sensors for detecting the influence and consequences of climatic changes. In combination 
with salinity, these factors are the predominant rulers of subsequent changes in the North 
Sea ecosvstems. 
This summer cruise provides BSH with the opportunity for monitoring the concentrations of 
additional environmental descriptors like oxygen, chlorophyll, nutrients and a variety of haz 
ardous substances. 
Another purpose of the summer cruise is monitoring of eutrophication parameters (nutrients, 
oxygen, transparency) and hazardous substances (pesticides in 2007) in the Greater North 
Sea for assessing the contamination of the German Bight within a wider perspective. These 
measurements are part of OSPAR’s Joint Assessment and Monitoring Programme JAMP.