30 | Cruise Report, RV ATAIR, Cruise 0671021-1, Bremerhaven - Thyboron —- Aberdeen, 18 Jul - 10 Aug 2023 
A respective ranking map (Figure 6.2) demonstrates that the western North Sea between 56°N 
and 59°N succumbed to the warmest or second warmest summer conditions observed be- 
tween 1997 and 2023. Conditions in the eastern half of the North Sea and regions surrounding 
the land masses of continental Europe were mostly normal. 
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60°N 
57°N 
54°N 
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Figure 6.2. Spatial distribution of the sea surface temperature (SST) ranking for summer 2023 (June. 
July and August), regionally indicating the n coldest/warmest summer SST since 1997. Source: BSH. 
Figures 6.3 and 6.4 highlight the potential temperature obtained from CTD measurements dur- 
ing cruise 067/021-1 near the suface (5 dbar) and near the bottom. The respective tempera- 
tures are also compared to a long-term mean field comprised of CTD data from the summer 
months of the years 2000 to 2020 (NSSS surveys 2000 to 2020, except year 2019). Based on 
the ship observations, temperatures warmer than 18°C were prominent along the German, 
Dutch and Belgians coasts (Figure 6.3, left). A band-like pattern with cooler temperatures of < 
15°C stretched along the eastern British coasts from the Shetland Islands to about 55°N. Also, 
the region east of the mouth of the Humber Estuary off the British coast showed a cool patch 
with temperatures < 15°C. The 16°C-isotherm showed a mostly meridional orientation north of 
57°N and was located off western Norway. Between 57°N and 53°N, the orientation changed 
to northeast-southwest dividing the North Sea into a warmer half in the east and cooler half in 
the west. Temperature deviations from the long-term mean (Figure 6.3, right) reveal warmer 
conditions mostly in the northwestern part of the North Sea, west and southwest of the Dogger 
Bank and along the Belgian, Dutch and German coasts. The location of the warmest temper- 
ature deviation seen in the CTD data at 5 dbar matches the one seen in the SST anomaly