Observations of Near-Surface Salinity and Temperature Structure with Dual-Sensor Lagrangian Drifters During SPURS-2

摘要

Sea surface salinity (SSS) is among the key indicators of air-sea buoyancy fluxes and the global hydrological cycle. Contributing to the second phase of the Salinity Processes in the Upper-ocean Regional Study (SPURS-2) carried out in the precipitation-dominated Intertropical Convergence Zone of the eastern Pacific, we deployed six Lagrangian drifters equipped with two pairs of temperature and conductivity sensors at 0.4 m and 5 m depth. Over the first three months, the drifter measurements revealed that (1) the wind strongly affects surface freshening resulting from rainfall and diurnal warming so that near-surface salinity and temperature gradients generally do not form at wind speeds greater than 7 m s(-1), (2) temperature and salinity differences between the two measurement depths are positively correlated for the cases of surface warming/salinification and freshening/cooling, (3) the lifetimes of rain-induced salinity anomalies can reach 24 hours, longer than previous estimates, (4) temperature (at 0.4 m and 5 m depth) and salinity (at 0.4 m depth) exhibit diurnal cycles, modulated by the wind, and (5) the differences that have been observed between satellite SSS and the standard uppermost salinity from Argo measurements are unlikely to be related to the difference in measurement depths (surface skin layer vs similar to 5 m depth).