Preliminary findings 
The following discussion of scientific results from the Summer North Sea Survey is based on 
OTD data from the real-time data processing, carried out during the cruise. These data were 
also sent to Copernicus in real-time. 
A delayed-mode final processing including an inspection of discrepancies between the CTD- 
measurements and water sample analyses will follow. The final, possibly corrected, CTD- 
data and a documentation of the delayed -mode processing will be archived at the DOD. 
Temperature: 
Appendix 3, figure 3.1 (top) shows the horizontal temperature distributions for the whole 
North Sea at the surface and bottom. Although the principal pattern, with highest values in 
the south to southeast at both layers, is similar to past years, absolute temperatures are up 
to 2 K lower. This is also reflected in the temperature anomaly to the reference period 2000- 
2010 (Figure 3.1, middle). At the surface the anomaly is overall negative, with values up to -2 
K in the central North Sea. In the past two years the North Sea was separated in an 
anomalously warm southern part and an anomalousliy cold northern part. At the bottom, the 
dattern of negative and positiv anomalies is comparable to summer 2019, but again less 
oronounNced by up to 2 K as to temperature levels. 
The BSH weekly and monthly analyses of sea surface temperature ” (sst) in the North Sea 
anable us to put the observations during the cruise in a broader context. The spatially 
averaged sst was warmer than in the reference period 1990 to 2015 and also sligthly warmer 
than in 2019 from Januar to June (Figure 2). At July the warming of the surface layer came to 
a halt in cold weather conditions with low solar radiation. This situation was surveyed during 
the CE20017A cruise. However, still at sea, on the way home, a change to warm weather 
was experienced. The heating of the water close to the surface resumed such strongly that 
the average sst of the North Sea has exceeded the multiannual mean of the reference period 
from August until now (November). 
The 2020 North Sea Summer Survey covered the last decade of July and the first decade of 
August. Evidently, (Figure 2, right panel) this survey took place prior to surface temperatures 
and vertical stratification reaching their seasonal peak. Unlike most of the other cruises done 
in the area (Table 1) the current survey was carried out 2 or 3 weeks too early in the 
summer. One has to keep this in mind when comparing the results from 2020 with past 
years. 
Weekly North Sea SST 1998 - 2020 
EL} 
18 
T 16 
4 
2 
8 
a 
de 
% 
Da an 
ba 
oa 
ei mn 
aan 190° 
"wan + 2 st 
an - 2 std 
ont means 20" 
—— Month means MN 
5.0 
Eh 
_- 
12.0 
10.0 
f 
4.0 
— 1998-2017 
=2018 
— 201% 
— 2020 
an feb mar apr may Jun Jul aug sep oct nov dec 9 1t 13.15 Deko 41 43 46 47 49 51 53 
Figure 2: Sseasonal signal of sst in the North Sea, based on monthly mean of NOAA satellite 
data (left), based on weekly mean of the BSH merged product from ship observations and 
NOAA satellite. 
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