DMI/ERGOM is coupled with a version the DMI North Sea - Baltic Sea ocean circulation model DMI-BSHcmod in high spatial resolution. DMI/ERGOM runs twice daily for a 60 hour marine ecology forecast.

DMI/ERGOM is initialized using marine ecology data from the ICES (International Council for the Exploration of the Sea) Oceanographic Data Centre. For time progression, DMI/ERGOM is forced with nutrient loadings from the following sources:

• North Sea riverine nutrient loadings as climatological monthly means
• Baltic river loadings, derived from the daily operational output of the hydrological HBV model run at the Swedish Meteorological Hydrological Institute (SMHI) for 43 Baltic catchment areas.
• atmospheric dry precipitation of nitrogen and phosphorus is neglected, as we focus on the annual cycle in the euphotic layers.
• open boundary conditions towards the Atlantic are configured using the climatology of ICES data.

DMI/ERGOM gives full 3-d information about nine state variables (see below), in a time resolution of one hour.

The forecast page presents some of this output:

• surface total chlorophyll-a
• surface Nitrate
• near-bottom dissolved oxygen

for the upcoming two days.

ERGOM was originally developed by Neumann et al. (2002) to feature the Baltic Sea Ecosystem. The model provides a full mathematical description of the behavior of marine ecology state variables due to these biogeochemical processes:

• photosynthesis
• grazing
• respiration
• mortality
• mineralization
• nitrification
• denitrification

ERGOM has nine state variables:

• dissolved nutrients
  • ammonium
  • nitrate
  • phosphate
• phytoplankton (primary production)
  • diatoms (grow in nutrient-rich conditions)
  • flagellates (grow in nutrient-poor conditions)
  • blue-green algae (cyanobacteria, fix atmospheric nitrogen)
• zooplankton (graze on phytoplankton)
• detritus (dead plankton, some of which enter the sediment)
• dissolved oxygen

ERGOM is nitrogen-based, and the balance of phosphorus/oxygen is based on nitrogen using stoichiometric Redfield ratios. The concentration of dissolved oxygen controls processes as denitrification and nitrification. Hydrogen sulfate is included as a deficit in the oxygen balance. Detritus in the sediment is either buried, mineralised or resuspended into the water column, depending on the velocity of near-bottom currents.

Neumann, T., Towards a 3-D ecosystem model of the Baltic Sea, J. Mar. Syst., 25, 405-419, 2000.

Neumann, T., W. Fennel, and C. Kremp, Experimental simulations with an ecosystem model of the Baltic Sea: A nutrient load reduction experiment, Global Biogeochemical Cycles, 16, 10.1029/2001GB001,450, 2002.