Low frequency circulation and coastal trapped waves propagation along chilean coasts

The present research, shows the coastal currents low frequency features off 30º S and 34º S, from november 1991 to august 1995, and evident propagation of coastal trapped waves in currents and sea level.

Currents from 30º S and 34º S at 170, 400, and 700 m depth were analyzed, together with sea level measured in tide stations at 27º, 30º, 33º, and 36.7º S. Current data was available at 30º S from JGOFS-Chile project (Joint Global Ocean Fluxes Study), and at 34º S from UCV-DGI 223.757 project (Shelf circulation on central Chile).

Data analysis, was based on determinations of Spectral density, Coherence and Phase functions, and through them, non dispersive coastal trapped waves phase velocity was calculated.

Results showed a persistent southward flow at 170 m at 30º S and 34º S, currents in both places had energetic fluctuations with periods of 40 days, 2 and one week. Sea level showed its most intense variability in periods of 70, 50, 25 and 10 days. This stands out the low frequency variability modulating influence on circulation.

Coastal trapped waves, with shelf waves features, introduced into the study area from the north, propagating along the coastal waves guide with phase velocities of 245 and 242 km/d, in sea level and alongshore flow, respectively.