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 ecosystem-circulation model including dissolvedorganic matter is used to estimate the dissolved organic nitrogen (DON)supply sustaining primary production in the subtropical north Atlantic Ocean.After an analysis of the coupled model performances compared to the data, asensitivity study demonstrates the strong impact of parameter values linkedto the hydrolysis of particulate organic nitrogen and remineralisation ofdissolved organic nitrogen on surface biogeochemical concentrations.The physical transport of dissolved organic nitrogen contributes to maintainthe level of primary production in this subtropical gyre. It is dominated bythe meridional component. We estimate a meridional net input of0.039 molN m−2 yr−1 over the domain (13–35° N and71–40° W) in the subtropical gyre. This supply is driven by theEkman transport in the southern part and by non-Ekman transport (meridionalcurrent components, eddies, meanders and fronts) in the northern part of thesubtropical gyre. At 12° N, our estimate (18 kmolN s−1)confirms the estimation (17.9 kmolN s−1) made by Roussenov etal. (2006) using a simplified biogeochemical model in a large scale model.This DON meridional input is within the range (from 0.05 up to0.24 molN m−2 yr−1) (McGillicuddy and Robinson, 1997; Oschlies,2002) of all other possible mechanisms (mesoscale activity, nitrogenfixation, atmospheric deposition) fuelling primary production in thesubtropical gyre. The present study confirms that the lateral supply ofdissolved organic nitrogen might be important in closing the N budget overthe north Atlantic Ocean and quantifies the importance of meridional input ofdissolved organic nitrogen.