Simulation of nutrient transport from different depths during an upwelling event in the Gulf of Finland**This work was sponsored by the Estonian Science Foundation (grant No. 7467 & grant No. 7328) and the Russian Foundation for Basic Research (grant No. 09-05-00479).

AbstractNumerical simulation experiments with a high-resolution circulation model were carried out to study nutrient transport from different depths to the surface 10-m layer during an upwelling event along the northern coast of the Gulf of Finland in July 1999. The initial nutrient distribution is based on field measurements performed in the north-western part of the Gulf. Wind forcing covering the period of the upwelling along the northern coast was turned through 180° to simulate an upwelling along the southern coast. The simulation results showed that the main phosphorus transport to the upper 10-m layer occurred from depths shallower than 30m for the upwelling events along both the northern and the southern coasts. Nitrogen transport to the upper 10-m layer was the largest from depths of 40–55m for the upwelling along the northern and 40–65m for the upwelling along the southern coast. Simulated cumulative volume transports to the upper 10-m layer from different depths showed that the contribution from deeper layers was larger in the case of the upwelling along the southern coast. The reduction of wind stress had a bigger influence on water transport from the deeper layers

A Simple Tool for the Early Prediction of the Cyanobacteria Nodularia Spumigena Bloom Biomass in the Gulf of Finland

A fuzzy logic model for predicting the maximum biomass of the toxic cyanobacteria Nodularia spumigena bloom in the Gulf of Finland is suggested. The model bloom biomass depends on the phosphate conditions up to15 June, including the excess phosphate left over after the spring bloom and on the phosphate inputs parameterised by wind mixing and upwelling from 1 May to 15 June. The surface layer temperature, set to vary from 14 to 23ºC, is regarded as a bloom regulating parameter. The model simulations showed that the predicted N. spumigena biomasses differ markedly from year to year and clearly depend on phosphate conditions up to 15 June.JRC.H.3-Global environement monitorin

Simulation of nutrient transport from different depths during an upwelling event in the Gulf of Finland

Numerical simulation experiments with a high-resolution circulation model were carried out to study nutrient transport from different depths to the surface 10-m layer during an upwelling event along the northern coast of the Gulf of Finland in July 1999. The initial nutrient distribution is based on field measurements performed in the north-western part of the Gulf. Wind forcing covering the period of the upwelling along the northern coast was turned through 180° to simulate an upwelling along the southern coast. The simulation results showed that the main phosphorus transport to the upper 10-m layer occurred from depths shallower than 30 m for the upwelling events along both the northern and the southern coasts. Nitrogen transport to the upper 10-m layer was the largest from depths of 40-55 m for the upwelling along the northern and 40-65 m for the upwelling along the southern coast. Simulated cumulative volume transports to the upper 10-m layer from different depths showed that the contribution from deeper layers was larger in the case of the upwelling along the southern coast. The reduction of wind stress had a bigger influence on water transport from the deeper layers

Late Summer Vertical Nutrient Fluxes Estimated from Direct Turbulence Measurements: a Gulf of Finland Case Study.

Abstract not availableJRC.H-Institute for environment and sustainability (Ispra

Model study on present and future eutrophication and nitrogen fixation in the Gulf of Finland, Baltic Sea

The response of nutrient and chlorophyll fields to climate change by the end of the twenty-first century was evaluated in the Gulf of Finland (Baltic Sea) using comparison of a hindcast simulation for 1997–2006 and future climate forcing, assuming an A1B greenhouse gas emission scenario and business-as-usual riverine nutrient load for 2090–2099. The comparison of simulated oxygen, phosphate and nitrate levels from the hindcast model with the measurements indicated a good performance of the 3D ecosystem model, except for overestimated nearbottom layer nitrates. The mean chlorophyll level was slightly overestimated by the model, whereas the variability in the surface layer chlorophyll level was well reproduced. Future projection simulations indicate no considerable changes in the upper layer oxygen concentrations compared with the hindcast simulation and observations, but deeper near-bottom layers were projected to become anoxic, causing an increase in phosphate and a decrease in nitrate concentrations in these layers. The increase in surface layer phosphate and the decrease in nitrate concentrations lead to an increase in summer cyanobacteria blooms and an increase in nitrogen fixation, which therefore led to an increase in the annual mean chlorophyll content in the upper layer.JRC.H.1-Water Resource

Analysis of Temporal Variability of Measured and Modeled Vertical Distributions of Salinity and Temperature in the Gulf of Finland during 10-Year Period

The Gulf of Finland is the sub-basin of the Baltic Sea seriously affected by eutrophication. General Estuarine Transport Model (GETM) was used for modeling hydrophysical fields of the Gulf during the period from 1997 to 2005. The results of the hydrodynamic modeling are important input for ecosystem modeling, in which salinity and temperature variations play the most important role. An accurately simulated salinity field is to some extent a proof that the transport of passive bio-chemical tracers can also be simulated correctly. In this study validation of the results of GETM is performed and comparison with Modular Ocean Model (MOM) is provided. These two models differ in numerical schemes that are used for solving the model equations, in model setup and to some extent in forcing. At first the time series of surface and bottom temperature and salinity from GETM are visually compared with measurements. Long-term measurement data from three HELCOM monitoring stations representing western, central and eastern parts of the Gulf were used. In this study we focus on Taylor diagram that provides quick summary of the degree of patterns correspondence and allows seeing how well model simulates natural pattern. For statistical analysis the surface temperature and salinity have been given the values at a depth of 5 m, and the bottom salinity and temperature are the corresponding values at the lowest depth (about 60 m) at which measurements were carried out. The validation results were grouped similarly for both models. Modeled surface temperature showed good agreement with observed data in all three stations. Root mean square error (RMSE) was between 0.2 and 0.4, correlation coefficients between 0.94 and 0.98 and normalized standard deviations between 0.9 and 1.1 for the both models. Thus, seasonal cycles in the upper layer were reproduced well. Bottom temperatures and surface and bottom salinities were reproduced with lower quality. Bottom temperatures were better reproduced in the western and central Gulf than in the eastern Gulf. Surface salinity was simulated with the same quality in all stations by GETM, while MOM reproduced salinity better in the central Gulf compared to the eastern and western part. Bottom salinities were better simulated by MOM than by GETM. The latter showed larger variability due to higher spatial resolution.JRC.DDG.H.3-Global environement monitorin