Stratification and mixing in the Chilean Inland Sea using an operational model

Abstract

The Chilean Inland Sea (CIS) is an extensive estuary system with a complex topography and many fjords and channels. The degrees of stratification and mixing in the CIS are strongly affected by river discharges, high levels of rainfall, wind, and tidal forces. Field and satellite observations have suggested that stratification and mixing fluctuate on different timescales and spatial scales, but the length and resolution of this record are insufficient to resolve these trends across the entire water column. We used an operational oceanographic forecasting model (MOSA) based on the Regional Ocean Modeling System (ROMS) to study the yearly and seasonal patterns of stratification and mixing in the CIS. The evaluation of the model showed a satisfactory response to the seasonal variability of temperature, salinity, and currents. The representation of the monthly stratification degrees of the system obtained with the buoyancy frequency and the potential energy anomaly reveals a highly dynamic estuary system with heterogeneous patterns on distinct spatial and temporal scales in the CIS. We conclude that the CIS can be classified into three zones: seasonal stratification regions, permanent stratification regions, and permanent mixing regions. Our results reveal a highly dynamic system that can be studied on different timescales with an operational model such as MOSA. This information may be relevant for studies of decade-scale fluctuations linked to climate change.