Quality Control and Application of Oxygen Data from Profiling Floats

Profiling floats provide a near-ideal platform for monitoring the seasonal evolution of both physical and chemical processes at the regional, basin, and global scale. Although temperature, salinity, and pressure data must pass well-defined Quality Control protocols at Global Data Assembly Centers, no such protocol exists for chemical data (oxygen and nitrate) now being measured on 348 “Argo Equivalents” (of which ~150 are still active) within the ~3200 float array. With the number of chemical measurements returned from the Argo array rapidly growing, it is important to develop and evaluate new QC procedures for these data in order to use the chemical Argo dataset for quantitative descriptions of oceanic biogeochemical processes. We initiated a preliminary assessment of quality control protocols for profiling float data, with the ultimate goal of using the QC'd dataset for biogeochemical studies, including use of float oxygen data to constrain a model that calculates rates of Net Community Production. Profiling float oxygen data prior to June 2010 were compared to the World Ocean Atlas 2009 monthly climatology. Large deviations from the climatology were observed for many floats, indicating the need for a QC protocol for float oxygen data, and possibly also indicating real processes not accounted for in the climatology. Approximately 100 floats were selected to calculate net community production in the euphotic zone. Here we discuss different QC methods that we have explored, and evaluate how each method affects the calculated NCP rates. Depending on which QC method is used, the sign of the NCP rates can change, thus further highlighting the importance of establishing a proper QC protocol for float oxygen data.