The physical characteristics of continental shelf waters off
Oregon during late winter and spring of 1975 are described and compared
with observations taken previously during summer. The currents
in winter are barotropic in the monthly means while in summer
the currents are baroclinic. Alongshore current fluctuations on the
time scale of a few days are depth dependent in winter but become
depth independent in summer. The current shear changes sign on the
several day time scale in winter while in summer the deeper currents
are always northward with respect to the near surface currents.
Alongshore coherences of sea level and currents indicate that
winter fluctuations generally propagate southward rather than northward
as previously observed in summer. These winter fluctuations in
alongshore currents also have onshore/offshore phase speeds that are
comparable in magnitude to their alongshore phase speeds. There is no
evidence for free continental shelf wave activity in winter although
forced waves (travelling predominately southward, as do the meteorological
disturbances) may exist. The Gill and Schumann (1974)
model, which predicts sea level from a knowledge of the alongshore
components of winds along the coastline, is tested for winter and
summer in 1975 and found to have some predictive ability for fluctuations
on the time scale of several days.
The transition from winter to summer is initiated in a dramatic
barotropic event and continues as a longer period baroclinic adjustment.
The former is marked by a sudden reversal of currents and a
lowering of sea level while the latter is marked by a slow rising of the
pycnocline and with it the layer of maximum vertical shear. Both the
barotropic changes at the transition event and the adjustment of the
density field, which occurs after the transition event, are directly
forced by the local wind. / Graduation date: 1977
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27739 |
| Date | 15 February 1977 |
| Creators | Sobey, Edwin J. C., 1948- |
| Contributors | Smith, Robert L. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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