Oxygen fluxes in the Norwegian Atlantic Current

Oxygen and phosphate measurements from two sections across the Norwegian At lantic Current, the Gimsoy-NW section from 67.5 degreesN 9 degreesE to 71.5 degreesN 1 degreesE and the Bjornoya-W section along 74.5 degreesN from 7 to 15 degreesE, are used to estimate oxygen fluxes in the surface layer and between the atmosphere and the ocean. Vertical entrainment velocities of 0 .9 m day(-1) for the winter season and 0.1 m day(-1) for the summer season are found and applied to the upper 300 m. The resulting oxygen fluxes to th e surface layer driven by this vertical mixing are 0.58 +/- 0.05 and 0.27 /- 0.02 mol O-2 m(-2) year(-1) at the Gimsoy-NW and Bjornoya-W sections, re spectively. Oxygen fluxes to the surface layer due to phytoplankton product ion are 2.6 and 3.4 mol O-2 m(-2) year(-1), which represent the net communi ty production at the two sections. Estimated uncertainties in these numbers are +/-15%. The surface water is a sink for atmospheric oxygen during fall and winter and a source during the productive season for both sections. On an annual basis there is a net uptake of oxygen from the atmosphere, 3.4 /- 0.4 mol O-2 m(-2) year(-1) at the Gimsoy-NW section and 4.9 +/- 0.5 mol O-2 m(-2) year(-1) at the Bjornoya-W. A decrease in temperature of 1 degree sC to 1.5 degreesC seen between the Gimsoy-NW section and the Bjornoya-W se ction is the main reason for the increased atmospheric flux of oxygen at th e latter section. An oxygen budget made for the area bounded by the two sec tions gives a net advective flux of oxygen out of the area of approximately 10 mol O-2 m(-2) year(-1). The increased concentration of oxygen correspon ding to the decrease in surface layer temperatures going northwards in the Norwegian Atlantic Current is mainly attributed to the air-sea oxygen excha nge and phytoplankton production in this area. (C) 2001 Elsevier Science B. V. All rights reserved.