Presented at the 2014 Ocean Sciences MeetingThe evolution of the upper ocean thermohaline structure was observed with Mixed Layer Lagrangian Floats (MLFs) during the NASA Salinity Processes in the Upper-Ocean Regional Study (SPURS). During the course of the experiment, two float deployments were accomplished, spanning a year from September 2012 to September 2013 (with a 1.5 month break in February and March). The floats conducted 4 to 12 daily profiles of salinity and temperature through the upper ocean boundary layer, resolving variability on timescales ranging from diel to seasonal. Variability of near-surface salinity at time scales shorter than a week is of particular interest, since it is not resolved with the present generation of remote sensing tools or the global array of Argo profiling floats. Our observations document multiple cases of such rapid changes, including formation and dissipation of low-salinity pools associated with strong precipitation events and diel modulation of surface salinity accompanying intermittent entrainment during the deepening of the mixed layer in late summer and fall. We describe scenarios of the boundary layer evolution during these events and the fluxes associated with them.