Ocean Science www.ocean-sci.net 1812-0784 1812-0792 6 2 2010 10.5194/os-6-461-2010 http://www.ocean-sci.net/6/461/2010/ http://www.ocean-sci.net/6/461/2010/os-6-461-2010.html http://www.ocean-sci.net/6/461/2010/os-6-461-2010.pdf 461 474 2010-04-26 Sensitivity of oxygen dynamics in the water column of the Baltic Sea to external forcing S. Miladinova svetla.miladinova@jrc.ec.europa.eu A. Stips CEC Joint Research Centre, Institute for Environment and Sustainability, Ispra (VA), Italy A 1-D biogeochemical/physical model of marine systems has been applied to study the oxygen cycle in four stations of different sub-basins of the Baltic Sea, namely, in the Gotland Deep, Bornholm, Arkona and Fladen. The model consists of the biogeochemical model of Neumann et al. (2002) coupled with the 1-D General Ocean Turbulence Model (GOTM). The model has been forced with meteorological data from the ECMWF reanalysis project for the period 1998–2003, producing a six year hindcast which is validated with datasets from the Baltic Environmental Database (BED) for the same period. The vertical profiles of temperature and salinity are relaxed towards both profiles provided by 3-D simulations of General Estuarine Transport Model (GETM) and observed profiles from BED. Modifications in the parameterisation of the air-sea oxygen fluxes have led to a significant improvement of the model results in the surface and intermediate water layers. The largest mismatch with observations is found in simulating the oxygen dynamics in the Baltic Sea bottom waters. The model results demonstrate the good capability of the model to predict the time-evolution of the physical and biogeochemical variables at all different stations. Comparative analysis of the modelled oxygen concentrations with respect to observation data is performed to distinguish the relative importance of several factors on the seasonal, interannual and long-term variations of oxygen. It is found that natural physical factors, like the magnitude of the vertical turbulent mixing, wind speed and the variation of temperature and salinity fields are the major factors controlling the oxygen dynamics in the Baltic Sea. The influence of limiting nutrients is less pronounced, at least under the nutrient flux parameterisation assumed in the model. Axell, L. B.: On the variability of Baltic Sea deep-water mixing, J. Geophys. Res., 103, 667–682, 1998. Blackford, J. C, Allen, J. I., and Gilbert, F. J.: Ecosystem dynamics at six contrasting sites: a generic modelling study, J. Marine Syst. 52, 191–215, 2004. Bonsdorff, E., Rönnberg, C., and Aarnio, R.: Some ecological properties in relation to eutrophication in the Baltic Sea, Hydrobiologia, 475/476, 371–377, 2002. Burchard, H., Petersen, O., and Rippeth, T. P.: Comparing the performance of the Mellor–Yamada and k–e two-equation closure models, J. Geophys. Res., 103, 10543–10554, 1998. Burchard, H., Bolding, K., Kühn, W., Meister, A., Neumann, T., and Umlauf, L.: Description of a flexible and extendable physical-biogeochemical model system for the water column, J. Marine Syst., 61, 180–211, 2006. Feistel, R., Nausch, G., and Hagen, E.: The Baltic inflow of autumn 2001, Meereswissenschaftliche Berichte, 54, 55–68, 2003a. Feistel, R., Nausch, G., Matthäus , W., and Hagen, E.: Temporal and spatial evolution of the Baltic deep water renewal in spring 2003, Oceanologia, 45(4), 623–642, 2003b. Feistel, R., Nausch, G., and Hagen, E.: Unusual inflow activity 2002/3 and varying deep-water properties, Oceanologia, 48(S), 21–35, 2006. HELCOM: Third periodic assessment of the state of the marine environment of the Baltic Sea, 1989–1993, Background document, Baltic Sea Environ. Proceeding No 64 B, Helsinki Commission, Helsinki, Finland, 1996. HELCOM: The Baltic marine environment 1999–200, Baltic Sea Environ. Proceeding No 87, Helsinki Commission, Helsinki, Finland, 2003. HELCOM: Activities 2006 overview, Baltic Sea Environ. Proceeding No 112, Helsinki Commission, Helsinki, Finland, 2007. IOW: Cruise Report of r/v "Alexander v. Humboldt", Cruise No 44/03/07, Baltic Sea Research Institute, Warnemünde, Germany, 2003. Jakobsen, F.: The major inflow to the Baltic Sea during January 1993, J. Marine Syst., 6, 227–240, 1995. Janssen, F., Neumann, T., and Schmidt, M.: Inter-annual variability in cyanobacteria blooms in the Baltic Sea controlled by wintertime hydrographic conditions, Mar. Ecol.-Prog. Ser., 275, 59–68, 2004. Kuznetsov, I., Neumann, T., and Burchard, H.: Model study on the ecosystem impact of a variable C:N:P ratio for cyanobacteria in the Baltic Proper, Ecol. Model., 219, 107–114, 2008. Kühn, W. and Radach, G.: A one-dimensional physical-biological model study of the pelagic nitrogen cycling during the spring bloom in the northern North Sea (FLEX `76), J. Marine Res., 55, 687–734, 1997. Laamanen, M., Fleming, V., and Olsonen, R.: Water transparency in the Baltic Sea between 1903 and 2004. FIMR, Indicators 2004, State of the Baltic Sea, HELCOM ((http://www.helcom.fi/environment2/ifs/archive/ifs2004/en_GB/transparency/)), 2004. Lass, H. U. and Mohrholz, V.: On dynamics and mixing of inflowing saltwater in the Arkona Sea, J. Geophys. Res., 108(C2), 3042–3057, doi:10.1029/2002JC001465, 2003. Liss, P. S. and Merlivat, L.: Air-sea exchange rates: introduction and synthesis, edited by: Buat-Menard, P., The role of air-sea exchange in geochemical cycling, Reidel, Dordrecht, 163–170, 1986. Matthäus, W. and Nausch, G.: Hydrographic-hydrochemical variability in the Baltic Sea during the 1990s in relation to changes during the 20th century, ICES Mar. Sci. Symp., 219, 132–143, 2003. Mohrholz, V., Dutz, J., and Kraus, G.: The impact of exceptionally warm summer inflow events on the environmental conditions in the Bornholm Basin, J. Marine Syst., 60, 285–301, doi:10.1016/j.jmarsys.2005.10.002, 2006. Neumann, T.: Towards a 3-D-ecosystem model of the Baltic Sea, J. Marine Syst., 25, 405–419, 2000. Neumann, T., Fennel, W., and Kremp, C.: Experimental simulations with an ecosystem model of the Baltic Sea: a nutrient load reduction experiment, Global Biogeochem. Cy., 16, 1033–1052, doi:10.1029/2001GB001450, 2002. Neumann, T. and Schernewski, G.: An ecological model evaluation of two nutrient abatement strategies for the Baltic Sea, J. Marine Syst., 56, 195–206, 2005. Neumann, T. and Schernewski, G.: Eutrophication in the Baltic Sea and shifts in nitrogen fixation analyzed with a 3-D ecosystem model, J. Marine Syst., 74, 592–602, 2008. Omstedt, A. and Axell, L.: Modeling the seasonal, interannual and long-term variations of salinity and temperature in the Baltic proper, Tellus, 50A, 637–652, 1998. Omstedt, A., Elken, J., Lehmann, A., and Picchura, J.: Knowledge of the Baltic Sea physics gained during the BALTEX and related programmes, Prog. Oceanogr., 63, 1–28, 2004. Reissmann, J.: On the representation of regional characteristics by hydrographic measurements at central stations in four deep basins of the Baltic Sea, Ocean Sci., 2, 71–86, www.ocean-sci.net/2/71/2006/, 2006. Reissmann, J., Burchard, H., Feistel, R., Hagen, E., Lass, H. U., Mohrholz, V., Nausch, G., Umlauf, L., and Wieczorek, G.: State-of-the-art review on vertical mixing in the Baltic Sea and consequences for eutrophication, Prog. Oceanogr., 82, 47–80, 2009. Sellschopp, J., Arneborg, L., Knoll, M., Fiekas, V., Gerdes, F., Burchard, H., Lass, U., Mohrholz, V, and Umlauf, L.: Direct observations of a medium-intensity inflow into the Baltic Sea, Cont. Shelf Res., 2393–2414, doi:10.1016/j.csr.2006.07.004, 2006. Stigebrandt, A.: A model for the vertical circulation of the Baltic deep water, J. Phys. Oceanogr., 17, 1772–1785, 1987. Stigebrandt, A.: Computations of oxygen fluxes through the sea surface and the net production of organic matter with application to the Baltic and adjacent seas, Limnol. Oceanogr., 36, 444–454, 1991. Stips, A., Bolding, K., Burchard, H., Djavidnia, S., and Peneva, E.: Realistic multiannual simulations of the coupled North Sea and Baltic Sea system using the GETM model, European Commission, EUR 21503 EN, 2005. Taylor, K. E.: Summarizing multiple aspects of model performance in a single diagram, J. Geophys. Res., 106, 7183–7192, 2001. Vichi, M., Ruardij, P., and Baretta, J. W.: Link or sink: a modelling interpretation of the open Baltic biogeochemistry, Biogeosciences, 1, 79–100, 2004. Wasmund, N., Nausch, G., and Matthäus, W.: Phytoplankton spring blooms in the southern Baltic Sea–-spatio-temporal development and long-term trends, J. Plankton Res., 20, 1099–1117, 1998. Weiss, R. F.: The solubility of nitrogen, oxygen and argon in water and seawater, Deep-Sea Res., 17, 721–735, 1970.