Importance of dissolved organic nitrogen in the North Atlantic Ocean in sustaining primary production: a 3-D modelling approach

摘要

An eddy-permitting coupled ecosystemcirculationmodel including dissolved organic matter is usedto estimate the dissolved organic nitrogen (DON) supply sustainingprimary production in the subtropical north AtlanticOcean.After an analysis of the coupled model performances comparedto the data, a sensitivity study demonstrates the strongimpact of parameter values linked to the hydrolysis of particulateorganic nitrogen and remineralisation of dissolvedorganic nitrogen on surface biogeochemical concentrations.The physical transport of dissolved organic nitrogen contributesto maintain the level of primary production inthis subtropical gyre. It is dominated by the meridionalcomponent. We estimate a meridional net input of0.039 molNm−2 yr−1 over the domain (13–35 N and 71–40 W) in the subtropical gyre. This supply is driven bythe Ekman transport in the southern part and by non-Ekmantransport (meridional current components, eddies, meandersand fronts) in the northern part of the subtropical gyre. At12 N, our estimate (18 kmolN s−1) confirms the estimation(17.9 kmolN s−1) made by Roussenov et al. (2006) using asimplified biogeochemical model in a large scale model. ThisDON meridional input is within the range (from 0.05 upto 0.24 molNm−2 yr−1) (McGillicuddy and Robinson, 1997;Oschlies, 2002) of all other possible mechanisms (mesoscaleactivity, nitrogen fixation, atmospheric deposition) fuellingprimary production in the subtropical gyre. The presentstudy confirms that the lateral supply of dissolved organicnitrogen might be important in closing the N budget over thenorth Atlantic Ocean and quantifies the importance of meridionalinput of dissolved organic nitrogen.