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Modelling the influence of Major Baltic Inflows on near-bottom conditions at the entrance of the Gulf of Finland.

Lessin G, Raudsepp U, Stips A - PLoS ONE (2014)

Bottom Line: We compared results of a realistic reference run to the results of an experimental run where Major Baltic Inflows were suppressed.Our experiment revealed that typical estuarine circulation results in the sporadic emergence of short-lasting events of near-bottom anoxia in the western Gulf of Finland due to transport of water masses from the Baltic Proper.Our results reaffirm the importance of accurate representation of salinity dynamics in coupled Baltic Sea models serving as a basis for credible hindcast and future projection simulations of biogeochemical conditions.

View Article: PubMed Central - PubMed

Affiliation: Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, United Kingdom.

ABSTRACT
A coupled hydrodynamic-biogeochemical model was implemented in order to estimate the effects of Major Baltic Inflows on the near-bottom hydrophysical and biogeochemical conditions in the northern Baltic Proper and the western Gulf of Finland during the period 1991-2009. We compared results of a realistic reference run to the results of an experimental run where Major Baltic Inflows were suppressed. Further to the expected overall decrease in bottom salinity, this modelling experiment confirms that in the absence of strong saltwater inflows the deep areas of the Baltic Proper would become more anoxic, while in the shallower areas (western Gulf of Finland) near-bottom average conditions improve. Our experiment revealed that typical estuarine circulation results in the sporadic emergence of short-lasting events of near-bottom anoxia in the western Gulf of Finland due to transport of water masses from the Baltic Proper. Extrapolating our results beyond the modelled period, we speculate that the further deepening of the halocline in the Baltic Proper is likely to prevent inflows of anoxic water to the Gulf of Finland and in the longer term would lead to improvement in near-bottom conditions in the Baltic Proper. Our results reaffirm the importance of accurate representation of salinity dynamics in coupled Baltic Sea models serving as a basis for credible hindcast and future projection simulations of biogeochemical conditions.

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Bathymetric map of the model domain.Locations of monitoring stations BY15 (57.32°N, 20.05°E, depth 238 m), LL17 (59.03°N, 21.08°E, depth 171 m), LL12 (59.48°N, 22.9°E, depth 82 m), LL7 (59.85°N, 24.84°E, depth 100 m) and LL3A (60.07°N, 26.35°E, depth 68 m) are shown. Location of the model open boundary in Kattegat is indicated by red line.
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pone-0112881-g001: Bathymetric map of the model domain.Locations of monitoring stations BY15 (57.32°N, 20.05°E, depth 238 m), LL17 (59.03°N, 21.08°E, depth 171 m), LL12 (59.48°N, 22.9°E, depth 82 m), LL7 (59.85°N, 24.84°E, depth 100 m) and LL3A (60.07°N, 26.35°E, depth 68 m) are shown. Location of the model open boundary in Kattegat is indicated by red line.

Mentions: The model domain covers the entire Baltic Sea area with an open boundary in the northern Kattegat (Fig. 1). Bathymetry was interpolated to a 2×2 nm (3704×3704 m) model grid from the digital topography of the Baltic Sea [31]. 25 layers were applied in the vertical, using adaptive coordinates. Adaptive coordinates are based on a vertical optimization of the layer distribution which depends on vertical density and velocity gradients and the distance to surface and bottom [20]. The time step implemented is 30 s for the barotropic and 600 s for the baroclinic mode. The period modelled is 01.01.1990–31.12.2009. During the first year of the simulation only hydrodynamics was modelled as a spin-up for the coupled hydrodynamic-biogeochemical simulation.


Modelling the influence of Major Baltic Inflows on near-bottom conditions at the entrance of the Gulf of Finland.

Lessin G, Raudsepp U, Stips A - PLoS ONE (2014)

Bathymetric map of the model domain.Locations of monitoring stations BY15 (57.32°N, 20.05°E, depth 238 m), LL17 (59.03°N, 21.08°E, depth 171 m), LL12 (59.48°N, 22.9°E, depth 82 m), LL7 (59.85°N, 24.84°E, depth 100 m) and LL3A (60.07°N, 26.35°E, depth 68 m) are shown. Location of the model open boundary in Kattegat is indicated by red line.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231095&req=5

pone-0112881-g001: Bathymetric map of the model domain.Locations of monitoring stations BY15 (57.32°N, 20.05°E, depth 238 m), LL17 (59.03°N, 21.08°E, depth 171 m), LL12 (59.48°N, 22.9°E, depth 82 m), LL7 (59.85°N, 24.84°E, depth 100 m) and LL3A (60.07°N, 26.35°E, depth 68 m) are shown. Location of the model open boundary in Kattegat is indicated by red line.
Mentions: The model domain covers the entire Baltic Sea area with an open boundary in the northern Kattegat (Fig. 1). Bathymetry was interpolated to a 2×2 nm (3704×3704 m) model grid from the digital topography of the Baltic Sea [31]. 25 layers were applied in the vertical, using adaptive coordinates. Adaptive coordinates are based on a vertical optimization of the layer distribution which depends on vertical density and velocity gradients and the distance to surface and bottom [20]. The time step implemented is 30 s for the barotropic and 600 s for the baroclinic mode. The period modelled is 01.01.1990–31.12.2009. During the first year of the simulation only hydrodynamics was modelled as a spin-up for the coupled hydrodynamic-biogeochemical simulation.

Bottom Line: We compared results of a realistic reference run to the results of an experimental run where Major Baltic Inflows were suppressed.Our experiment revealed that typical estuarine circulation results in the sporadic emergence of short-lasting events of near-bottom anoxia in the western Gulf of Finland due to transport of water masses from the Baltic Proper.Our results reaffirm the importance of accurate representation of salinity dynamics in coupled Baltic Sea models serving as a basis for credible hindcast and future projection simulations of biogeochemical conditions.

View Article: PubMed Central - PubMed

Affiliation: Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, United Kingdom.

ABSTRACT
A coupled hydrodynamic-biogeochemical model was implemented in order to estimate the effects of Major Baltic Inflows on the near-bottom hydrophysical and biogeochemical conditions in the northern Baltic Proper and the western Gulf of Finland during the period 1991-2009. We compared results of a realistic reference run to the results of an experimental run where Major Baltic Inflows were suppressed. Further to the expected overall decrease in bottom salinity, this modelling experiment confirms that in the absence of strong saltwater inflows the deep areas of the Baltic Proper would become more anoxic, while in the shallower areas (western Gulf of Finland) near-bottom average conditions improve. Our experiment revealed that typical estuarine circulation results in the sporadic emergence of short-lasting events of near-bottom anoxia in the western Gulf of Finland due to transport of water masses from the Baltic Proper. Extrapolating our results beyond the modelled period, we speculate that the further deepening of the halocline in the Baltic Proper is likely to prevent inflows of anoxic water to the Gulf of Finland and in the longer term would lead to improvement in near-bottom conditions in the Baltic Proper. Our results reaffirm the importance of accurate representation of salinity dynamics in coupled Baltic Sea models serving as a basis for credible hindcast and future projection simulations of biogeochemical conditions.

Show MeSH
Related in: MedlinePlus