Dissolved organic carbon (DOC) taken from discrete water column samples collected between October and April at Palmer Station, 2002-2012.

Dissolved organic carbon (DOC) is a poorly-characterized but large and dynamic pool of actively-cycling carbon in the oceans, and one of the largest organic carbon pools on the planet. The total DOC pool consists of three major fractions: refractory DOC resistant to microbial oxidation with a turnover time of millennia; semi-labile DOC, produced and decomposed on seasonal timescales, and labile DOC, consisting of simple, recently-produced compounds with nanomolar concentrations, and turnover times of minutes-days. The background concentration of refractory DOC in the deep ocean is 35-45 micromolar. DOC concentration in the upper 100-200 meters is enhanced by 10-50 micromolar with the addition of semilabile DOC. In subtropical and temperate oceans, semilabile DOC can form an important part of the carbon export by deep vertical mixing into the oceanic mid-depths. Concentrations of semilabile DOC are lower in the polar Southern Ocean than in most other regions.