Annual Net Community Production in the Western Subtropical North Pacific Determined from Argo-O2 Measurements

Export of organic carbon from the surface ocean to depth (the biological pump) helps maintain the pCO₂ of the atmosphere and the O₂ content of the oxygen minimum zones of the ocean. In the upper ocean, at steady state over a seasonal cycle the net organic carbon export is equal to the Annual Net Community Production (ANCP). The geographic distribution of this quantity determined by satellite-predicted Net Primary Production (NPP) and the recycling efficiency in the euphotic zone is more heterogeneous than the limited experimental estimates of ANCP. We evaluate the relationship between these two estimates of ANCP in the subtropical Western North Pacific Ocean (~165^o E and ~20^o N) using oxygen measurements on Argo Floats. In January of 2015 we deployed four floats with Anderaa oxygen sensors attached to a ~60 cm stick on top of the float end cap, which can be readily calibrated against atmospheric pO₂. We present data from these floats and air-sea oxygen flux calculations. The degree of oxygen supersaturation in summer is 1-2 percent, and in winter it fluctuates between being over and undersaturated. Evaluating the role of bubbles in winter is critical to an accurate determination of the annual flux. While there is not a full year of data at the time of writing this abstract, there will be when the Ocean Science meeting is held. So far, after nine months of measurements, there is a net flux of oxygen to the atmosphere, indicating that photosynthesis exceeds respiration. In February we will present a full annual cycle of air-sea oxygen flux and an estimate of ANCP in this very rarely studied region of the ocean.