Multiscale Variability of Upper-Ocean Salinity in Eastern Pacific Fresh Pool

Nan-hsun Chi, Applied Physics Laboratory University of Washington, Seattle, WA, United States, Andrey Y. Shcherbina, Applied Physics Laboratory, Seattle, WA, United States and Luc Rainville, University of Washington, Seattle, WA, United States
The Eastern Pacific Fresh Pool (EPFP) is a band of relatively fresh surface waters in eastern tropical Pacific established in part by precipitation-dominant Intertropical Convergence Zone (ITCZ). The freshwater is integrated into the Eastern Pacific water mass structure through the multi-scale advection and turbulent mixing, which are still not well understood. Analyzing horizontal variability and vertical structure of the upper ocean salinity can help identifying the processes controlling freshwater redistribution and their relative importance. The Salinity Processes in the Upper-ocean Regional Study 2 (SPURS-2) field experiment took place in 2016 – 2017 in the EPFP. In addition to two month-long research vessel cruises, nearly 200 elements of moored, self-navigating, and drifting instrumentation formed a distributed autonomous observing system around the nominal “central” mooring site at (10°N, 125°W). We analyze 15 months of SPURS-2 in-situ observations to improve the understanding of the near surface salinity distribution in EPFP on scales from minutes to days and 0.1 to 100km. A wide range of salinity observations are synthesized and characterized using several statistical metrics: the spatial-temporal covariance functions, decorrelation scales in time and space, etc. Statistics of in-situ observations are compared with those derived from the satellite remote sensing products of the sea surface salinity, highlighting the relationship between different spatial-temporal scales and variabilities. This work is part of the SPURS-2 synthesis project looking at the multi-scale integration of freshwater into the upper Easter Pacific Ocean.