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Changes in apparent oxygen removal in the Baltic proper deep water
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
2000 (English)In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 25, no 3-4, 421-429 p.Article in journal (Refereed) Published
Abstract [en]

By developing a steady state diagnostic model for a stratified deep-water mass, one is able to quantify both the mass flows and apparent oxygen removal in the Baltic proper deep water. The model is based on continuity of the assumed conservative observable volume, salinity and temperature. Second degree polynomials are fitted to observed vertical profiles of temperature as well as oxygen concentration to give a functional correspondence with the used spatial variable salinity. These relations are used in the model that calculate the water flows, oxygen flows and oxygen removal during four periods between 1959 and 1997. The model forms a boundary value problem, which is solved with a finite difference scheme. The model seems to give reasonable estimates of the flows. The oxygen removal is mainly balanced by inflow of oxygen with incoming water. The oxygen consumption is 4-8 ╡1 O2 1-1 day -1, which corresponds to a degradation of organic matter in the range 30-60 g C m-2 year-1. (C) 2000 Elsevier Science B.V.

Place, publisher, year, edition, pages
2000. Vol. 25, no 3-4, 421-429 p.
Keyword [en]
oxygen, modelling, Baltic Sea
National Category
Social Sciences Interdisciplinary
Identifiers
URN: urn:nbn:se:liu:diva-30618DOI: 10.1016/S0924-7963(00)00031-2Local ID: 16210OAI: oai:DiVA.org:liu-30618DiVA: diva2:251441
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Modelling organic matter dynamics in aquatic systems
Open this publication in new window or tab >>Modelling organic matter dynamics in aquatic systems
2000 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Organic matter is a small but active part of the global carbon cycle. About one third is stored in the oceans where it has a relatively short residence time. The rest is found in the terrestrial biomass and in the soil. Aquatic systems exchange C02 with the atmosphere. Autotrophic organisms fix C02 into their biomass, while heterotrophic organisms respire C02 when utilising organic matter. Systems with large supply of organic matter by inflow can be net heterotrophic, which thus release more C02 than what they fix.

Two systems are studied, the Lake Ortrasket in northern Sweden and the Baltic Sea. In the Baltic primary production is the main source of organic matter, while in the lake dissolved organic matter from inflow dominates. Other characteristics of the Baltic Sea are that it is brackish and has a long residence time compared to the freshwater lake. These systems are studied with different types of models.

For the Baltic proper deep water, an inverse model of the water, salt and heat fluxes was used to estimate an oxygen budget including oxygen consumption. The oxygen levels in the Baltic proper deep water are critical due to the low supply and large consumption. The oxygen consumption is mainly due to organic matter degradation. The low oxygen and salinity levels in the Baltic have consequences for, among other things, the cod spawning success.

The lake model is a mechanistic model of dissolved organic carbon based on a Lagrangian fluid particle model and a one-dimensional physical model. The results show that Lake Ortrasket is a net heterotrophic system. In spite of the differences between the systems, both seems to have similar organic matter degradation rates, ~50 g C m-2 yr-1.

To supplement, time series of phosphate concentration were studied in the Baltic proper surface layer. These show seasonal variations coupled to the primary production, and this time dependence was modelled. The main purpose of the model is to complete corrupt observation time series, which is useful for environmental model studies.

Place, publisher, year, edition, pages
Motala: Kanaltryckeriet, 2000. 77 p.
Series
Linköping Studies in Arts and Science, ISSN 0282-9800 ; 214
Keyword
Vatten, Kol, Oceanografi, Hydrologi
National Category
Social Sciences Interdisciplinary
Identifiers
urn:nbn:se:liu:diva-32133 (URN)17993 (Local ID)91-7219-825-7 (ISBN)17993 (Archive number)17993 (OAI)
Public defence
2000-09-22, Hörsal Planck, Fysikhuset, Universitetsområdet Valla, Linköping, 10:00 (Swedish)
Supervisors
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2014-08-27Bibliographically approved

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Rahm, Lars

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