Conferencia: "Tidal and near-tidal motions in a patagonian fjord"

Se invita a docentes, estudiantes y público en general a la conferencia «Tidal and near-tidal motions in a patagonian fjord», dictada por la Dra(c) Lauren Ross de University of Florida,  el día miércoles 27 de agosto a las 17:00 hras en la sala Minera Escondida de la Facultad de Ciencias Naturales y Oceanográficas.
Patrocinada por: Programa de Financiamiento Basal COPAS Sur-Austral y Departamento de Oceanografía Universidad de Concepción.

Abstract

A series of observations are combined with analytical solutions to study tidal and near-tidal hydrodynamics in a Chilean Patagonia fjord. A two-month long time series of current velocities and echo intensity, together with along-channel hydrographic profiles of temperature and salinity, revealed  semidiurnal internal tides for the first time in Chilean fjords. High pulses in river discharge modulated the generation of these internal tides, which is another novel finding. Another data set spanned 8 months from Austral fall to spring in the same fjord. These data were complemented by regional atmospheric pressure and wind velocity measurements. Results revealed that extreme low-pressure events (<900 hPa) produced sustained westerly winds with synoptic period between 7 and 28 days, which in turn created a wind-induced setup toward the head of the fjord. This setup triggered internal waves (depressions of the pycnocline) at near lunar-monthly tidal periodicity (27.55 days). A three-dimensional analytical model of tidal flow in fjord-like basins was developed to understand tidal dynamics. This model included a width that decays exponentially with along-channel position. Model results showed standing tidal wave behavior within the fjord with an attenuation of the sea level toward the head due to the funnel-like width of the basin. Also, when the friction parameter was small, as is the case for Martinez Channel, strongest (>50cm/s) axial velocity was found near the sides of the channel. As friction increased, a more typical along-channel flow regime was found with highest velocities in the center of the basin. Lateral circulation gyres developed during slack flood and ebb tides due to the influence of Coriolis. This implies that significant lateral and vertical velocities are required to conserve mass in the system when Coriolis is influential. The lateral flows are thought to be influential in transport and residual circulation. This model can be applied to other fjords with similar scaling parameters.