Tlen (model EcoSat)

Dissolved oxygen concentration in water calculated using the EcoSat ecohydrodynamic model. Maps of oxygen concentrations with a resolution of 1 km are obtained by spatial interpellation of the results of the EcoSat model, whose spatial resolution is from about 5.5 km. Calculations using the model are performed on 18 layers of variable thickness, which allows to calculate the distribution of vertical oxygen concentrations at various depths. In the SatBałtyk System service distributions of oxygen concentration at the surface and at different depths are reported in grams of oxygen per cubic meter [gm^-3], four times a day.

Methodology for determining oxygen concentrations in the EcoSat model

The three-dimensional eco-hydrodynamic model EcoSat is modernized as part of the project SatBałtyk version of the numerical model ProDeMo[1][2]. The most important change was the inclusion of the DESAMBEM algorithm in the primary production calculations . The hydrodynamic part of the model (PM3D) is based on the model POM (Princeton Ocean Model) calculates hydrodynamic conditions: currents, water temperature and salinity based on forecasts from the numerical weather model UM (Unified Model) running in ICM of the University of Warsaw. PM3D works operationally, assimilating currently incoming satellite data about surface water temperature (SST) determined from AVHRR or MODIS radiometers.

The source of oxygen in sea water is the process of photosynthesis, as well as oxygenation as a result of gas exchange with the atmosphere. During the destruction of organic matter, oxygen is consumed. This process can lead to an oxygen deficit. In the absence of dissolved oxygen, the oxygen contained in the sulphates is consumed, producing hydrogen sulphide. The conceptual diagram of the ecological part of the model is shown in the figure. The model takes into account 18 state variables covering in the water column: 5 groups of phytoplankton, zooplankton, nutrients, carbon and organic forms of nitrogen, phosphorus and silicon in detritus, dissolved oxygen and hydrogen sulfide.

In the sediment, the model takes into account biogenic substances (nutrients) dissolved in pore waters, organic compounds reaching from the water column as detritus and undergoing aerobic mineralization in the upper part of the sediment, and denitrification and anaerobic degradation in the lower layers. Concentrations of dissolved oxygen, hydrogen sulfide and sulfates. In addition to the organic forms of carbon, nitrogen, phosphorus and silicon, the model also takes into account inorganic compounds of phosphorus with iron, which disintegrate under reducing conditions, as well as very stable compounds of phosphorus with aluminum and calcium.

In the area of the entire Baltic Sea, the EcoSat model has a resolution of 3 nautical miles (approx. 5.5 km). The model is operational and takes into account the influx of solar radiation calculated taking into account current satellite data from the model SolRad.

Validation (accuracy assessment)

The accuracy of determination of dissolved oxygen concentrations in the Baltic Sea using the EcoSat model was assessed on the basis of the difference in concentrations calculated using the model and measurements made by monitoring carried out under ICES in the years 2010-2014. The statistical error, expressed as the standard deviation of these differences, was estimated at 1.16 g m^-3. The bias (average difference) is 0.18 g m^-3.

Links to the parameter in the SatBałtyk System:

Tlen: 0m (model EcoSat)

Tlen:3m (model EcoSat)

Tlen: 5m (model EcoSat)

Tlen: 10m (model EcoSat)

Tlen: 20m (model EcoSat)

Tlen: 30m (model EcoSat)

[1] Ołdakowski B., Kowalewski M., Jędrasik J. Szymelfenig M., 2005, Ecohydrodynamic Model of the Baltic Sea, Part I: Description of the ProDeMo model, Oceanologia, 47 (4), 477–516

[2] Kowalewski M., 2015, The flow of nitrogen into the euphotic zone of the Baltic Proper as a result of the vertical migration of phytoplankton: An analysis of the long-term observations and ecohydrodynamic model simulation, Journal of Marine Systems, 145, 53-68, DOI 10.1016/j.jmarsys.2015.01.003