Space Observation of Carbon Dioxide Partial Pressure at Ocean Surface

Abstract

We have developed and validated a statistical model to estimate the partial pressure (or fugacity) of carbon dioxide at the sea surface from space-based observations of sea surface temperature, chlorophyll, and salinity. More than a quarter million in situ measurements coincident with satellite data were compiled. A portion of the data was randomly selected to train and validate the model. We have produced and made accessible nine years (2002–2011) of the partial pressure at 0.5° and daily resolutions over the global oceans. The outputs are found to be sensitive to variability from intraseasonal to interannual time scales and from the equatorial to high-latitude oceans. They can capture known phenomena, such as, annual spring blooms at high latitudes, interannual episodes of El Nino, and westward propagation of tropical instability waves. The feasibility of using a single algorithm to map the partial pressure over global oceans for all seasons is demonstrated. The result is important for characterizing the sources and sinks of atmospheric greenhouse gas and ocean biogeochemistry. We discuss the significance of the Advanced Scanning Microwave Radiometer in the consistent measurement of sea surface temperature, which is the main driver of ocean carbon dioxide change, in cold and warm waters, under clear and cloudy sky. The continuous and consistent coverage of the partial pressure over global ocean using space-based data is discussed.