Net community production and oxygen fluxes in the Nordic Seas based on O2 budget calculations

Abstract

Historical hydrographic data from 1955 to 1988 are applied to an oxygen model for the euphotic zone in an attempt to estimate the net community production in the Nordic Seas (Greenland, Iceland, and Norwegian Seas). The model requires prior knowledge of the net annual oxygen flux through the sea surface, which is achieved by an oxygen budget based on volume transports from the literature and observed oxygen concentrations. A net annual uptake of approximately 2.3 mol O2 m−2 is needed to balance the budget, indicating that the region acts as a sink for atmospheric oxygen. An oxygen budget for the euphotic zone is then compiled on the basis of observed monthly mean changes in oxygen content, which are assumed to be balanced by net air‐sea oxygen exchange and net community production. Vertical exchange through the bottom of the euphotic zone and horizontal transports are ignored. The mean net community production in the Nordic Seas is found to be 36 g C m−2 y−1, but this result is sensitive to variations in the calculated oxygen fluxes which arise from the uncertainty of the parameterization of the air‐sea gas exchange.