Diffusive component of the vertical flux of particulate organic carbon in the North polar Atlantic

The diffusive component of the vertical flux of particulate organic carbon (POC) from the surface ocean layer has been estimated using a combination of the mixed layer model and ocean color data from the SeaWiFS satellite. The calculations were carried out for an example location in the north polar Atlantic centered at 75◦N and 0◦ E for the time period of 1998–2004. The satellite estimates of surface POC derived using a regional ocean color algorithm were applied as an input to the model driven by local surface heat and momentum fluxes. For each year of the examined period, the diffusive POC flux was estimated at 200-m depth from April through December. The highest flux is generally observed in the late fall as a result of increased heat loss and convectional mixing of surface waters. A relatively high diffusive POC flux is also observed in early spring, when surface waters are weakly stratified. In addition, the model results demonstrate significant interannual variability. The highest diffusive POC flux occurred in 1999 (about 4500 mg m−2 over the 9-month period). In 1998 and 2002 the estimated flux was about two orders of magnitude lower. The interannual variability of the diffusive POC flux is associated with mixed layer dynamics and underscores the importance of atmospheric forcing for POC export from the surface layer to the ocean’s interior.