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Buoyancy-Driven Coastal Currents off Oregon during Fall and Winter

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Title Buoyancy-Driven Coastal Currents off Oregon during Fall and Winter
Names Mazzini, Piero L. F. (creator)
Barth, John A. (creator)
Shearman, R. Kipp (creator)
Erofeev, A. (creator)
Date Issued 2014-11 (iso8601)
Note This is the publisher’s final pdf. The published article is copyrighted by the American Meteorological Society and can be found at: http://journals.ametsoc.org/loi/phoc.
Abstract During fall/winter off the Oregon coast, oceanographic surveys are relatively scarce because of rough
weather conditions. This challenge has been overcome by the use of autonomous underwater gliders deployed
along the Newport hydrographic line (NH-Line) nearly continuously since 2006. The discharge from the
coastal rivers between northern California and the NH-Line reach several thousands of cubic meters per
second, and the peaks are comparable to the discharge from the Columbia River. This freshwater input
creates cross-shelf density gradients that together with the wind forcing and the large-scale Davidson Current
results in strong northward velocities over the shelf. A persistent coastal current during fall/winter, which the
authors call the Oregon Coastal Current (OCC), has been revealed by the glider dataset. Based on a two-layer
model, the dominant forcing mechanism of the OCC is buoyancy, followed by the Davidson Current and then
the wind stress, accounting for 61% (±22.6%), 26% (±18.6%), and 13% (±11.7%) of the alongshore
transports, respectively. The OCC average velocities vary from 0.1 to over 0.5 m s⁻¹, and transports are on
average 0.08 (±0.07) Sverdrups (Sv; 1 Sv = 10⁶ m³ s⁻¹), with the maximum observed value of 0.49 Sv, comparable
to the summertime upwelling jet off the Oregon coast. The OCC is a surface-trapped coastal current,
and its geometry is highly affected by the wind stress, consistent with Ekman dynamics. The wind stress has an
overall small direct contribution to the alongshore transport; however, it plays a primary role in modifying the
OCC structure. The OCC is a persistent, key component of the fall/winter shelf dynamics and influences the
ocean biogeochemistry off the Oregon coast.
Genre Article
Topic Circulation/Dynamics
Identifier Mazzini, P. L. F., Barth, J. A., Shearman, R. K., & Erofeev, A. (2014). Buoyancy-Driven Coastal Currents off Oregon during Fall and Winter. Journal of Physical Oceanography, 44(11), 2854-2876. doi:10.1175/JPO-D-14-0012.1

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