Seiche excitation in a highly stratified fjord of southern Chile: the Reloncaví fjord
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 lo...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-02-01
|
| Series: | Ocean Science |
| Online Access: | http://www.ocean-sci.net/13/145/2017/os-13-145-2017.pdf |
| Summary: | 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 (<i>c</i>) using two
approximations: (1) a simple reduced gravity model (RGM) and (2) a
continuously stratified model (CSM). No major seasonal changes in <i>c</i> were
observed using either approximation (e.g., the CSM yielded
0.73 < <i>c</i> < 0.87 m s<sup>−1</sup> for mode 1). The natural
internal periods (<i>T</i><sub>N</sub>) were estimated using Merian's formula for a
simple fjord-like basin and the above phase speeds. Estimated values of
<i>T</i><sub>N</sub> 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 (<i>T</i><sub>d</sub>) was relatively long (<i>T</i><sub>d</sub> = 9.1 days). |
|---|---|
| ISSN: | 1812-0784 1812-0792 |