MERCATOR OCEAN JOURNA, 
SEPTEMBER 2021 
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igure 8; Salinity from the HBM (left) and the NEMO (right) systems, plotted along with available observations from profile moorings in the 
3otland Deep area 
In 2019, the wave production system was further improved 
with offline coupling to surface currents produced by the 
Baltic MFC physical forecast. Overall, coupling effects to 
the wave field were small. In certain situations though, the 
difference in the significant wave height with and without 
coupling to the currents was up to 60 cm (Kanarik et al., 
2021). Also, in the Gulf of Finland, the refraction of swell, 
induced by currents, improved the peak period and the 
swell and wind sea energies. 
1.2 The Green Ocean 
For simulations of the green ocean the ERGOM (Ecological 
Regional Ocean Model) model is used. ERGOM is a well- 
known bio-geo-chemical model developed with focus on 
che Baltic Sea biochemical dynamics (Neumann, 2000). It 
jdescribes the basic nitrogen and phosphorus cycle through 
15 main state variables: 
- three different functional phytoplankton species, 
two groups of zooplankton and detritus, 
labile dissolved organic nitrogen, 
- total alkalinity (TA), 
dissolved inorganic carbon (DIC), 
ammonium, nitrate, phosphate, silicate and oxygen 
{see Figure 4). 
Primary production, Chlorophyll and Secchi depth are 
calculated diagnostically. The sediment is not vertically 
resolved and consists of two nutrient state variables 
Since 2015, several additions have been made into the 
Baltic MFC biogeochemical model system. For example, a 
new optical module has been added that also includes the 
labile dissolved organic nitrogen as a new state variable. 
ihe new module enables a more detailed calculation 
of turbidity and subsequent Secchi depth (Neumann et 
al., 2015). Furthermore, the net primary production was 
implemented as another diagnostic variable. Last but not 
least, a rudimentary iron circle has also been implemented. 
Ihe most extensive addition to the Baltic MFC 
biogeochemical model system was made with the 
zarbonate system in 2018. This was done following basically 
Kuznetsov and Neumann (2013) and Zeebe and Wolf- 
Sladrow (2001). TA and DIC are two prognostic parameters 
used to calculate the biogeochemical processes influence 
on the carbonate system (see also Schwichtenberg et al., 
2020). Respiration and primary production increase and 
decrease DIC. TA is mainly affected by river run-off and 
changes in nutrient concentrations. Both TA and DIC are 
required for the calculation of the diagnostic variables pk 
and pCO,. The carbonate system also includes exchange 
with annually iIncreasing and seasonally variable 
atmospheric CO, concentrations (see Figure 4)