A modeling study of hydrographic and flow variability along the river-influenced coastal ocean off central Chile

The coast of central Chile has multiple rivers with a marked seasonal discharge variability. Few studies have addressed primarily the seasonal variability of river plume extension and vertical structure. Here, we have analyzed the effects of multiple river outflows on the hydrography (salinity and density) and meridional transports off central Chile. This study is focused on synoptic and intraseasonal scales of variability using eight years of semi-realistic model outputs. Our results reveal that the plume spreading is much broader during winter than spring. Wind-driven changes in plume shapes modulate the geostrophic component of the flow field off Biobío and Itata rivers in winter (spring) after downwelling (upwelling) favorable winds. The geostrophic flow was important off Mataquito and Maule rivers after upwelling-favorable winds, primarily in spring. The stratification in winter was mostly associated with the freshwater content in all coastal regions and showed a rapid response to the wind stress forcing. The mixing through wind stress decreased in spring, modifying the stratification and uncoupling the wintertime variability between stratification and freshwater.