Moored instrument records, drogue displacements, and hydrographic
observations are used in describing the coastal currents and
upwelling off Peru. The data were obtained over the continental shelf
near 15°S. during a two week study in late March and early April of
1969.
First order statistics and graphical representations of current
meter time series indicate that the longshore flow was poleward during
most of the study period, interrupted by a three day 'event' of
equatorward flow. The similarity of flow at all current meters indicates that the field of flow as quasi-barotropic. The depth, extent, and transport of poleward flow indicated by current meter time series
and geostrophic sections were similar to those described in the literature
for the Peru-Chile Undercurrent. The observations suggest
that this flow moved further offshore as equatorward flow appeared
over the shelf.
Power spectral analyses performed on current meter records
indicate the existence of semidiurnal tidal currents in the longshore
direction. The magnitude of these currents is estimated at 10% to
15% of period mean speeds.
Ten meter drogue displacements are compared with 25 m recorded
currents and with winds. The observations indicate that: the
drogues were affected by both the 25 m flow and the wind; the depth
of the wind drift layer was between 10 m and 25 m; the drogue displacements were in the sense expected from the Ekman model.
Vertical sections of sigma-t, oxygen, and nitrate indicate the
existence of conditions consistent with upwelling. Surface maps of
temperature, nitrate, and chlorophyll 'a' over the shelf are used to
define the horizontal field of upwelling and its variations in time.
The distributions suggest that upwelling existed throughout the period
and underwent temporal and spatial modulations in intensity. The
possibility of a causal mechanism between observed current and
upwelling variations is examined.
Vertical salinity sections indicated the presence of a weak salinity
minimum between the surface and 100 m. It is suggested that this
minimum manifests the remnants of a tongue of Subantarctic Water
embedded in a much larger mass of Equatorial Subsurface Water.
The occurrence of the minimum only in conjunction with poleward flow
suggests that the water was advected or mixed coastward somewhere
north of the area studied, was entrained in the Peru-Chile Undercurrent,
and was carried south again. / Graduation date: 1970
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28954 |
| Date | 01 May 1970 |
| Creators | Enfield, David B. |
| Contributors | Smith, Robert L. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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