The data set consists of SeaFlow-based cell abundance, cell size (equivalent spherical diameter) and carbon biomass for picophytoplankton populations, namely the cyanobacteria Prochlorococcus, Synechococcus and small-sized Crocosphaera (2-5 um), and picoeukayotes phytoplankton and nanophytoplankton (2-5 μm ESD). SeaFlow is an underway flow cytometer that provides continuous shipboard observations of the optical properties of the smallest phytoplankton. The instrument collects the equivalent of 1 sample every 3 minutes or every 1 km (for a ship moving at 10 knots) from the ship’s flow-through seawater system. Since 2010, the instrument has been operated for 14,000 hours across 140,000 km of ocean, collecting over 300,000 samples in surface waters. Further information can be found on the SeaFlow website SeaFlow_allstats_vX,X_DATE.zip: contains SeaFlow data for each individual cruise, as described in Ribalet et al. (2019). SeaFlow_cmap_vX.X_DATE.xlsx: contains only "best" estimates of SeaFlow data, formatted for Simons CMAP datase.

This work was supported by grants from the Simons Foundation (#574495 to FR, #329108 to EVA and AEW, and #426570SP and #549894 to EVA), the Gordon and Betty Moore Foundation (#3776 to EVA) and the National Aeronautics and Space Administration (#80NSSC17K0561 to FR)