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 
vetween 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 
orofiles and water samples. 
Between the fixed CTD-stations a towed CTD-system (1998-2008 the BSH system Delphin, 
since 2009 an EIVA ScanFish MK IN oscillated between a depth of 3-10 m (depending on 
weather and sea state) and about 5 metres above the bottom in order to record the 3- 
dimensional distribution of relevant oceanographic parameters. Both CTD-systems recorded 
data for temperature, salinity, fluorescence (chlorophyll-a, yellow substance), and oxygen 
concentration. If available, ship mounted sensors recorded fluorescence, temperature, and 
salinity at about 4 m depth. Since 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. 
for nutrients, salinity, oxygen, pH) and with 10 litre and 100 litre glass spheres for organic 
contaminants. Surface samples for the detection of artificial nuclides were taken at all station. 
Preliminary results: 
The following preliminary results are compiled from ScanFish raw data. Final results will be 
oresented after data reprocessing and post-cruise calibration. Due to technical problems with 
voth ScanFish systems and W5 winch only results for the area between 54 and 57°N can be 
oresented. 
Temperature 
In 2013 the warm surface layer has a depth of 25 to 30 m which exhibits a widely 
homogeneous temperature distribution and a sharp thermocline at its lower boundary. Along 
the 56 and 57°N sections the bottom layer includes unusually water with temperatures below 
5©. In this area the temperature distribution diff ers significantly from the 10-year average 
2000 — 2010 (without 2002) and from the preceding years. 
Compared to 2012 the surface layer is warmer in 2013, but the bottom layer is colder. The 
total heat budget of the North Sea can be calculated not before the reprocessing of the CTD 
station data. The monthly averaged North Sea SST for August 2013 exceeded the long-term 
mean (1971-1993) by 1.2 K. 
Salinity 
Between about 1 and 2.5°E a small wedge of Atlantic Water (AW) >35 PSU intruded from 
ıhe North down to 56° N, which shows a vertical ext ension from the surface to bottom. In 
orevious years AW advanced as far as 56°N only in the bottom layer. Estimates concerning 
the salinity distribution in the northern part of the North Sea and the Baltic Outflow are not 
vossible before the processing of the CTD station data. 
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