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Volume 13, issue 1
Ocean Sci., 13, 145–160, 2017
https://doi.org/10.5194/os-13-145-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ocean Sci., 13, 145–160, 2017
https://doi.org/10.5194/os-13-145-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 17 Feb 2017

Research article | 17 Feb 2017

Seiche excitation in a highly stratified fjord of southern Chile: the Reloncaví fjord

Manuel I. Castillo1,2, Oscar Pizarro2,3,4, Nadin Ramírez2,4, and Mario Cáceres1 Manuel I. Castillo et al.
  • 1Escuela de Biología Marina, Facultad de Ciencias del Mar y de Recursos Naturales, Universidad de Valparaíso, Valparaíso, Chile
  • 2COPAS-Sur Austral, Universidad de Concepción, Concepción, Chile
  • 3Departamento de Geofísica, Universidad de Concepción, Concepción, Chile
  • 4Instituto Milenio de Oceanografía, Universidad de Concepción, Concepción, Chile

Abstract. We describe a seiche process based on current, temperature, and sea-level data obtained from the Reloncaví fjord (41.6° S, 72.5° W) in southern Chile. We combined 4 months of acoustic Doppler current profiler (ADCP) data with sea-level, temperature, and wind time series to analyze the dynamics of low-frequency (periods > 1 day) internal oscillations in the fjord. Additionally, seasonal conductivity, temperature, and depth (CTD) data from 19 along-fjord stations were used to characterize the seasonality of the density field. The density profiles were used to estimate the internal long-wave phase speed (c) using two approximations: (1) a simple reduced gravity model (RGM) and (2) a continuously stratified model (CSM). No major seasonal changes in c were observed using either approximation (e.g., the CSM yielded 0.73 < c < 0.87 m s−1 for mode 1). The natural internal periods (TN) were estimated using Merian's formula for a simple fjord-like basin and the above phase speeds. Estimated values of TN varied between 2.9 and 3.5 days and were highly consistent with spectral peaks observed in the along-fjord currents and temperature time series. We conclude that these oscillations were forced by the wind stress, despite the moderate wind energy. Wind conditions at the end of winter gave us an excellent opportunity to explore the damping process. The observed damping time (Td) was relatively long (Td =  9.1 days).

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Here we present the results of an intensive physical oceanography study conducted in the Reloncavi fjord (41.5º S, 72.5º W) which was focused on the sub-inertial timescale. The along-fjord currents presented 3-day oscillations which were consistent with the natural internal period of oscillation of the fjord basin (internal seiche). This oscillation could explain more than 44 % of the 3-day variability and contributed with kinetic energy levels as large as the tidal currents.
Here we present the results of an intensive physical oceanography study conducted in the...
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