Ocean Dynamics
Ö Springer
60°N
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56°N
54°N
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60°N
58°N
56°N
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3°W 0° 3°E 6°E 9°E 12°E 3°W 0° 3°E 6°E 9°E 12°E
Fig. 14 Temporally averaged MME mean (left) and standard deviation (right) of SSS in the North Sea in 2014. The black line marks the contour line of
standard deviation 1, which proceeds approximately along the salinity front of 34
This has already been detected in previous studies (Rodhe 1998;
Hordoir et al. 2013). The contour line marking the standard de
viation of 1 proceeds approximately along the salinity front of 34.
Such patterns have also been found in comparisons of climate
models (Biilow et al. 2014). It reflects the difficulties in simulat
ing the low-salinity fronts in the Norwegian Costal Current.
The daily spatial averages of SSS from the MME products
and the individual forecasts in the North Sea are compared in
Fig. 15. Systematic offsets can be detected between the time
series from the different forecasts. The salinities from
METNOROMS are much higher than those from the other
forecasts, accounting for 35.6. Except for summer time, the
MyOcean product (METUKFOAM) has the lowest salinities
of about 34.2. The values from the remaining models vary
between 34.5 and 34.9. As mentioned in Sect. 2.1, the Baltic
outflow in the models ROMS and FOAM AMM is defined as
large river input with the eastern boundary located in the Kat
tegat, whereas the magnitude of river runoff possibly differs
between these models. The different extensions of the model
grids and different boundary conditions might play an impor
tant role in the uncertainty for this region.
Between middle of June and middle of August, the salinities
from almost all models, except METNO ROMS and
METUK FOAM, drop strongly, reaching a spread of 0.8.
SMFH HIROMB NS03 shows a marked decline with salinities
decreasing by 0.7 from about 34.5 to 33.8. In comparison, the
values from the other forecasts decrease by about 0.2 and 0.5.
Except during summer, the salinities of the MME products are
about 34.7, following the seasonal pattern reflected by the en
semble members (Fig. 15). The values of the MME mean also
Fig. 15 Daily spatial averages of SSS from the MME mean, MME median (black lines), and the individual forecasts in the North Sea in 2014. The
ensemble spread (¿standard deviation) is indicated by the yellow-shaded field. The number of forecasts is marked as phis sign