The Subtropical Ocean's Biological Carbon Pump Determined From O2 and DIC/DI13C Tracers

The ocean's biological organic carbon pump regulates the pCO(2) of the atmosphere and helps maintain the oxygen distributions in the ocean. Global models of this flux are poorly verified with observations. We used upper-ocean budgets of O-2 and the C-13/C-12 of dissolved inorganic carbon (DIC) to estimate the biological pump in the subtropical gyres. These two tracers yield, within errors, similar result (similar to 2.0 mol C.m(-2).year(-1)) at three Northern Hemisphere subtropical locations. Values for three Southern Hemisphere subtropical regions are lower and more variable determined by the O-2 mass balance than by the (DIC)-C-13 method (-0.5 to 0.8 mol C.m(-2).year(-1) and 0.9 to 1.3 mol C.m(-2).year(-1), respectively). Both methods suggest that the subtropical ocean is, on the whole, autotropic. The gas exchange residence times of O-2 and dissolved inorganic carbon result in different spatial and temporal averaging creating complementary tracers for biological pump model verification.