Abstract

The Chilean Patagonia, between 40 degrees S and 56 degrees S, hosts one of the world's largest and most productive estuarine systems, where oceanic waters mix with freshwater from rivers, runoff, glaciers, and snowmelt, creating a complex and dynamic estuarine environment. Understanding the factors influencing salinity fluctuations in this region is key to elucidating its ecosystem complexity. This study evaluates the forcings driving salinity variability in the mixed layer of West Patagonia's coastal zone. A salinity balance was done using GLORYS reanalysis and atmospheric variables from ERA5. Spatiotemporal variability of the salt balance terms was investigated using Hovm & ouml;ller diagrams focusing on three key sites. Results showed significant seasonal and interannual variability in the mixed layer. Advective terms, particularly the zonal component, were crucial in modulating salinity. A clear annual cycle emerged in the northern sector (40-48 degrees S). Empirical Orthogonal Function analysis identified significant interannual fluctuations, with positive atypical periods in 1997-2005 and 2010-2015, and negative periods in 2006-2008 and 2018-2020. These fluctuations were primarily linked to the dynamics of San Quint & iacute;n Glacier (similar to 47 degrees S), which induced anomalous salinity conditions along the coastal domain. Notably, these variations did not exhibit a direct relationship with large-scale climate modes. These findings underscore the intricate nature of salinity variability in West Patagonia's coastal waters, driven by a complex interplay of local hydrological processes and glacial dynamics. Understanding these mechanisms is essential for anticipating future changes in this fragile and ecologically significant region.