Anhang 1: English Summary

In 1998 the Federal Maritime and Hydrographic Agency (BSH, Bundesamt für Seeschifffahrt
und Hydrographie) started its annual summer surveys which cover the entire North Sea
between 52° and 60° N. The surveys were realised at a time when thermal stratification is
expected to be at its maximum and phytoplankton production has passed its maximum (see
Table 1). The surveys include seven coast to coast East-West sections between 54°and 60°
N and additional stations between 54° N and the ent rance of the English Channel. With the
exception of the first survey in 1998 all surveys served a fixed station grid for vertical CTD
and water samples. Between the fixed CTD-stations a towed CTD-system (1998-2008 the
BSH system Delphin, since 2009 an EIVA ScanFish Il) oscillated between a depth of 3 - 10
m (depending on weather and sea state) and a about 5 metres above the bottom in order to
record the 3-dimensional distribution of relevant oceanographic parameters. Both CTDsystems
 sampled T, S, fluorescence (chlorophyll-a, yellow substance), and oxygen
concentration. Additionally, a thermosalinograph and optical sensors were mounted in the
ship moon pool at about 4 m depth. In 2010 the survey was extended to the north in order to
record the transition area between the northern North Sea and the eastern North Atlantic.
Additionally, water samples were collected by means of a CTD-rosette sampler-system (e.g.
nutrient, salinity, oxygen, pH) and with a MERCOS sampler for heavy metals (10 m depth).
Surface samples for the detection of artificial nutrients were taken at all station and deep
samples up to 1000 m with a 270-I-sampler at station 59 and 60.
Preliminary results:
Due to the long and cold winter the surface layer of the southern and central North Sea is
thinner and less warm compared to the preceding year. The gradient of the thermocline is
much smoother and parts of the shallow south-eastern German Bight — which are normally
vertically homogeneously heated down to the bottom — show a stratification.
The area northwards of the Skagerrak, which is strongly influenced by the NE-Atlantic,
corresponds widely to the long-term condition.
The massive intrusion of Atlantic Water down to the Jutland coast in 2009 was not observed
in 2010.

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