Annual carbon fluxes in the upper Greenland Sea based on measurements and a box-model approach

Measurements of nitrate and the carbonate system parameters performed mainl y From 1993 to 1997 have been used to estimate the evolution of the concent ration fields over the year in the surface and underlying waters of the cen tral Greenland Sea. This, together with synoptic surface wind data From the NCEP/NCAR reanalysis project, is used to evaluate the vertical mixing, the biological production and decay, as well as the air-sea exchange of CO2 in the region. Tn the winter season, the vertical mixing dominates the change of the nitrate concentration in the surface water. The mixing factor estim ated for this season is used to compute the addition of chemical constituen ts to the surface water from below. The residual nitrate concentration chan ge, after the mixing contribution has been subtracted, is attributed to bio logical production or decay. The computations are performed with a 1-day re solution and initially the advective contribution is neglected, as the hori zontal gradients in the central Greenland Sea gyre are small. Following thi s approach, the air sea flux of CO2 is directed into the sea all year aroun d, with an annual uptake of 53 +/- 4 g C m(-2) yr(-1) for the years 93 to 9 7. The carbon flux as driven by biology shows a strong primary production p eak around Julian day 140 followed by a decrease which turns into decay of organic matter at about day 200. Summarizing the biological activity in the surface water over the year gives a new production of 34 g C m(-2) yr(-1). The vertical flux of dissolved inorganic carbon into the surface water fro m below amounts to 11 g C m(-2) yr(-1). The build up of carbon in the surfa ce water, 30 g C m(-2) yr(-1), is explained by that the temperature of the outflowing water is approximately 2 degrees C colder than the inflowing wat er, giving a higher dissolved inorganic carbon concentration as a result of the increase in the solubility of carbon.