Compilation of Summaries 
21 
tied areas, the temperature difference between the warm surface layer and the 
bottom water increased by approximately 2 К compared to 2009. At 20-30 m, 
the surface layer thickness was considerably lower than in the previous year 
and the maximum gradients in the thermocline were also considerably lower at 
1.5 К/m. A sharp thermocline was only to be found on the 55° N and on the 
56° N sections east of Dogger Bank. Due to the lower thickness of the surface 
layer, the cooler bottom water could cover a larger volume, meaning that the 
entire heat content of the North Sea declined again and was close to the 
10-year average. 
The vertically mixed ribbon of warm water parallel to the continental coast con 
tinued to cool (approx. 1 K) in 2011. In the stratified areas, the difference be 
tween the warm surface layer and the bottom water decreased from 10 К to 
8 К with respect to 2010. The maximum surface layer depth was 40 m; the 
thermocline gradients were between 0.5 and 2.5 К/m. Compared to 2010, the 
overall heat content of the North Sea increased slightly and exceeded the 
10-year average by 0.4 standard deviations. 
The vertical temperature distribution in the German Bight and its evolution 
in time was documented using data from the station “German Bight” of the 
BSH Marine Environmental Monitoring Network. The positive anomaly of the 
2007/2008 winter minimum with a deviation of approximately 2 К as a result of 
the heat surplus from the preceding summer and autumn months was one of 
the dominant signals in the reporting period. The winter minima came closer to 
the climatological values again in the winter of 2008/2009. The summer max 
ima of the daily averages are up to 3 К above the climatology. The stratification 
was particularly pronounced in 2010. The surface and bottom temperature dif 
ferences measured up to 8 K, while the seasonal maximum was reached in the 
surface layer approximately 6 weeks before that of the bottom layer. The pro 
nounced stratification was caused by the unusually high atmospheric heat in 
puts in April 2010 and the following summer. In 2011, the summer’s solar ra 
diation gains were significantly lower than the long-term average. This led to a 
lower summer maximum and a weakly developed stratification. 
Salinity (Page Seite 134 et seq.) 
In summer 2008, the second-highest total salt content since 1999 was re 
corded with 2004 at maximum. During winter 2008 Atlantic Water (AW S > 35) 
penetrated from the northern boundary southwards until 56° N in the bottom 
and surface layer. In the summer, the 35 isohaline in the bottom layer ran 
roughly along the 57° N parallel and AW with S > 35.35 penetrated southwards 
down to 58° N in a broad tongue and covered a considerably larger volume 
than during the previous year. At the surface, the area with AW only covered the 
area north of 57° N and west of the prime meridian. 
In the winter of 2009, the AW advanced southwards down to 55° N in the entire 
water column. At the same time, a large, lens-shaped body of AW was located 
in the inflow area of the Channel. During the summer period, the tongue of AW 
reached still southwards until approximately 56° N, but was significantly nar 
rower at the surface than during winter. The total salt content decreased slightly 
in comparison to the previous year. In 2008 and 2009, the total volume of water