On the coupling of benthic and pelagic biogeochemical models
Soetaert, K.; Middelburg, J.J.; Herman, P.M.J.; Buis, K. (2000). On the coupling of benthic and pelagic biogeochemical models. Earth-Sci. Rev. 51: 173-201 In: Earth-Science Reviews. Elsevier: Amsterdam; Lausanne; London; New York; Oxford; Shannon. ISSN 0012-8252; e-ISSN 1872-6828, more |  |
| Keywords | Chemical elements > Nonmetals > Atmospheric gases > Nitrogen
Chemical elements > Nonmetals > Atmospheric gases > Oxygen
Chemistry > Geochemistry > Sediment chemistry
Cycles > Chemical cycles > Geochemical cycle > Biogeochemical cycle
Cycles > Chemical cycles > Geochemical cycle > Biogeochemical cycle > Nutrient cycles > Carbon cycle
Environments > Aquatic environment > Benthic environment
Environments > Aquatic environment > Pelagic environment
Layers > Water column
Particulates > Suspended particulate matter
Sediment-water exchanges
Topographic features > Submarine features > Continental shelves
Marine/Coastal |
| Abstract | Mutual interaction of water column and sediment processes is either neglected or only crudely approximated in many biogeochemical models. We have reviewed the approaches to couple benthic and pelagic biogeochemical models. It is concluded that they can be classified into a hierarchical set consisting of five levels, differing in the amount of detail given to the sediment processes. The most complex approach (level 4) fully couples water column processes to a vertically resolved biogeochernical sediment model. First simplification is achieved by using a vertically integrated dynamic sediment model (level 3); next is a reflective type of boundary (level 2) where particulate material arriving at the sediment surface is instantaneously transformed into dissolved components. Then comes a set of models in which either the bottom-water concentration of dissolved substances or the sediment-water exchange is imposed (level 1). Finally, in some biogeochemical models, the bottom is plainly ignored (level 0). We have tested these various approaches in a coupled physical-pelagic-benthic biogeochemical model for oxygen, nitrogen and carbon cycling in continental shelf areas. We discuss the various model approaches with respect to their impact on the pelagic system and point out some of the inconsistencies hidden in certain formulations. We conclude that lower boundary types, in which sediment fluxes or concentrations are imposed (level 1), are especially badly designed because they fail to assure conservation of mass. Finally, we suggest as best choice a level 3 approach in which the evolution of sedimentary particulate matter is part of the solution and where the bottom fluxes of dissolved constituents are parameterised based on mass budget considerations. These simplified formulations represent the best balance between computational demand and attained accuracy. |
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