Determination of primary production as part of OSMOSIS using vertically profiling gliders

Marine phytoplankton fix approximately half of all global Primary Production (PP). In situ measurements of PP in the open ocean are often sparse, therefore satellite derived PP is important for global coverage. However these estimates rely on cloud free skies and observe only the first optical depth of the euphotic zone, often omitting features such as subsurface chlorophyll maxima. We show that high resolution profiles of light and chlorophyll fluorescence from Seagliders can be used to estimate depth resolved marine primary production. Using this method, we have calculated the full annual cycle of chlorophyll and PP from a number of Seaglider deployments in the North Atlantic, capturing both small scale spatio-temporal changes in PP and subsurface production. The annual cycle shows a peak of 3 gC m^-2 d^-1 in PP in July followed by the formation of a subsurface production maximum. Comparisons are made between Seaglider estimates of primary production, in situ ship samples and satellite derived values, to show the power of this glider based approach. It is therefore now possible to measure PP at resolutions of a few metres and hours, spanning periods of months to years, and capturing everything from submesoscale phenomena to seasonal change.