Oxygen in the deep basins of the Baltic Sea: The influence of winter mixing

St. John, M. A., Lehmann, Andreas, Hinrichsen, Hans-Harald and Mackenzie, B. R. (1996) Oxygen in the deep basins of the Baltic Sea: The influence of winter mixing [Paper] In: ICES Council Meeting 1996, 27.9.-04.10.1996, Reykjavik, Iceland.

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Variations in oxygen conditions below the permanent halocline influences the Baltic ecosystem through a number of mechanisms. Principle among these are fluctuations in the availability of benthic habitat suitable for Baltic cod (the top predator in the Baltic ecosystem). Variations in the volume of deep
oxygenated water influences dircetly the potential feeding habitat and volume of water suitable for spawning. Recent research has identified the importance of inflows of saline, oxygen rich North Sea water into the Baltic sea on the recruitment success of Baltic cod. These inflows increase the volume of water with suitable oxygen and salinity conditions for the development and survival of cod eggs (termed
spawning volume). Increases in the "spawning volume" have occurred with out the occurrence of a major inflow from the North Sea (e.g. 1958-59; 1966-67). Other candidate processes suggested to potentially increase the "spawning volume" include variations in timing and volume of terrestrial runoff, advection of water from the Arkona Basin, convective overturning of the water column due to surface cooling as well as wind mixing down to the halocline. In order to examine the latter three mechanisms, we have
performed model simulations utilizing the Baltic Sea Model (Lehmann, 1995). Three-dimensional fields of temperature and salinity were obtained from field studies in July 1995 and interpolated onto the model grid, atmospheric forcing data was obtained from EUROPA-Model. The BaItic Sea model was then run from the period from July 24 to December 31, 1995. To test the effects of increased wind energy and surface cooling on oxygen conditions below the permanent halocline variations in the oxygen conditions were examined utilizing the following experiment conditions;
a) a reduction of SST by 5 oe over the entire simulation period thereby increasing vertical convection.
b) an increase of surface wind energy over the modeled period by 15%.
c) two high energy winter storms
The results of these simulations and the possible implications of the effects of these processes on the reproductive environment of Baltic cod will be discussed.

Document Type: Conference or Workshop Item (Paper)
Keywords: BaItic Sea, cod spawning volume, oxygcn, 3-D modeling, convection, wind mixing
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EV Marine Evolutionary Ecology
Refereed: No
Date Deposited: 18 Feb 2008 17:23
Last Modified: 07 May 2020 07:50
URI: http://eprints.uni-kiel.de/id/eprint/7972

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