Estimation of the along-shore flow in Peru-Chile Undercurrent

Title: Estimation of the along-shore flow in the Peru-Chile
Undercurrent and its inter-annual seasonal and along-shore
variability.

The Humboldt Current system, bound by the steep continental slope
and narrow shelf of western South America, is one of the four major
Eastern Ocean Boundary Current systems of the world. Equator-ward
winds predominate during most of the year north of about 33S, driving
a large coastal upwelling system that extends from central Chile to
northern Peru. The large scale mean circulation and water properties
distribution is consistent, in general, with a Sverdrup balance, while
the physical coastal environment is dominated by the coastal
upwelling, the persistent subsurface pole-ward Peru-Chile Undercurrent
(PCU) and inter-annual variability related to El Nino-Southern
oscillation (ENSO) and intra-seasonal, remotely-forced coastal-trapped
waves.

During the last 3 years (1997-2000), current measurements from two
sites near 30S, started in 1991, continued with the support of the
FONDAP-Humboldt programme. The time-series will cover the period from
November 1991 to September 2000, including the 1991-92 and the strong
1997-98 El Nino, as well as the 1995-96 and the 1998-99 La Nina. One
recording current meter (RCM)is located in the deep ocean at about
150km off the coast in a water depth of ~4200m with 5 Aanderaa RCM's
located at 100m, 400m, 900m, 1900m and 3400m. The other mooring lays
over the slope at ~15km from the coast in a water depth of ~850m. The
latter line has 3 RCM's, at 220m, 450m and 750m. During 1998, a new
mooring (equipped with 3 Aanderaa RCM's located at 240m, 450m and 750m
depth and one upward looking ADCP situated at 120m) have been
maintained over the slope off northern Chile around 21S. In addition,
a hydrographic transect, extending about 170km offshore, near 30S, has
been occupied regularly twice a year since November 1991.