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

The ocean's biological organic carbon pump regulates the p CO 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 13 C/ 12 C of dissolved inorganic carbon (DIC) to estimate the biological pump in the subtropical gyres. These two tracers yield, within errors, similar result (~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 DI 13 C 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.