Improved estimates of air-sea oxygen fluxes and biological carbon export through the use of self-calibrating Argo oxygen floats in the Pacific
Bushinsky, Seth Michael
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The production and consumption of oxygen during photosynthesis and respiration stoichiometrically links oxygen and organic carbon in the surface ocean. Oxygen sensors are currently being deployed on profiling floats throughout the ocean, which has the potential to greatly expand the extent of in situ oxygen measurements and our understanding of biological processes in the ocean. Inaccuracies in current oxygen sensors due to instrument drift currently limit the utility of these floats for estimating air-sea oxygen fluxes. This thesis describes in situ calibrations of oxygen sensors on profiling floats through atmospheric measurements and the use of this data towards understanding oxygen and organic carbon cycles in the Pacific. We deployed 12 modified Argo floats equipped with Aanderaa oxygen optodes in the Pacific: one at Ocean Station Papa (OSP) in the northeast Pacific, 10 in the Kuroshio Extension (KE), and one in the south subtropical Pacific near Samoa. Air oxygen measurements after each float profile were used to accurately calibrate the optodes and correct for drift observed in approximately ½ of the optodes over >2 years. I interpret these oxygen data using two methods. At OSP, I developed a 1-dimensional abiotic gas model for use with oxygen data to determine the annual net community production (ANCP). I found that summertime production was roughly balanced by wintertime net heterotrophy and that estimates of bubble-induced, air-sea exchange and diapycnal diffusion at the base of the mixed layer were important to interpretation of oxygen fluxes. In the KE I interpreted data from multiple floats to determine mean annual cycles of supersaturation and air-sea oxygen fluxes from biogeochemical regions. While the magnitude of the abiotic oxygen fluxes in winter is too high to quantify ANCP in this area, I calculated summertime production and winter subduction from the regional oxygen data. This work represents an improvement in our ability to remotely measure in situ oxygen and new methods of interpretation so that a global array of oxygen sensors on profiling floats can be used to quantify the marine oxygen and carbon cycles.
- Oceanography