Dissolved organic carbon in North Atlantic surface waters

Dissolved organic carbon (DOC) was analyzed by high temperature catalytic oxidation at 3 stations in the North Atlantic.The stations were chosen to cover a range of environments in the mixed layer, from coastal water in Roseway Basin on the Scotian Shelf to water from the seaward edge of the Scotian Slope and finally to open ocean water in the western Sargasso Sea.At 2 of the stations (Roseway Basin and Slope), the DOC revealed in surface waters by high temperature catalytic oxidation appeared to be biologically labile.DOC was positively correlated with chlorophyll and inversely correlated with apparent oxygen utilization (AOU).An inverse relationship between DOC and AOU was also found in deep water from the open ocean.This was in agreement with results from earlier analyses, but the negative slope of DOC with AOU was less than expected from the previous measurements.A relatively simple picture of the lability of DOC in the mixed layer was not always apparent in Roseway Basin or the open ocean.Horizontal advect~on and biological patchiness in weakly stratified surface waters contributed to large day-to-day vanations in the DOC profiles.This vanability should be taken into account when DOC is included in models of carbon cycling in the upper ocean.