Biological Oxygen Production in the Pacific Subtropical Gyres using Glider Surveys

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ABSTRACTOCE-0223372Experimental evaluations of the organic carbon export from the euphotic zone of the ocean are essential for verifying and calibrating estimates of the ocean's biological pump by both satellite color and Global Circulation Models. Studies of upper ocean oxygen mass balance have shown that carbon export from the euphotic zone can be accurately estimated by determining net annual biological oxygen production at locations where there are time-series measurements. Growing awareness of the present importance of nitrogen fixation in the subtropical North Atlantic and Pacific Oceans has lead to the suggestion that ocean productivity, and perhaps the organic carbon export, in these areas is limited by the wind blown flux of iron to the surface waters. One could evaluate the importance of this process in the subtropical ocean without the expense of an iron fertilization experiment by determining the net biological oxygen production in locations that receive very different atmospheric loading of iron. The ideal locations to contrast in this regard are the North and South Pacific Ocean; however, it has not been possible to carry out a time-series study south of the equator in the Pacific because it is too remote. The advent of glider technology and the evolution of our ability to quantify air-water gas exchange in the subtropical oceans make it now possible to study the oxygen mass balance by remotely measuring the T, S, and O2 concentrations in the upper ocean. In this study, investigators at the University of Washington will develop this new technology to determine the net biological oxygen production in the North and South Pacific. The subtropical oceans are ideal for introducing a glider study of upper ocean heat, fresh water and oxygen budgets because the relatively steady and slow surface currents.Specifically, the goals of this research are to demonstrate the utility of gliders to determine accurate and precise T, S and O2 concentrations in the open ocean from which budgets can be calculated and to contrast the net biological oxygen production in the North and South Pacific subtropical gyres. The research team will carry out glider surveys of the upper ocean at the Hawaii Ocean time series (HOT). The team will calibrate instruments on the glider against monthly measurements by the time-series scientists so that it will be possible to verify accuracies and make adjustments to improve results.