Document Type

Article

Publication Date

January 2014

Publication Title

Journal of Physical Oceanography

Volume

44

Issue Number

1

First Page

319

Last Page

342

DOI

10.1175/JPO-D-13-095.1

Keywords

Geographic location/entity, Continental shelf/slope, Circulation/Dynamics, Baroclinic flows, Coastal flows, Models and modeling, Model evaluation/performance, Variability, Intraseasonal variability, Seasonal variability

Disciplines

Marine Biology

Abstract

The California Undercurrent (CUC), a poleward-flowing feature over the continental slope, is a key transport pathway along the west coast of North America and an important component of regional upwelling dynamics. This study examines the poleward undercurrent and alongshore pressure gradients in the northern California Current System (CCS), where local wind stress forcing is relatively weak. The dynamics of the undercurrent are compared in the primitive equation Navy Coastal Ocean Model and a linear coastal trapped wave model. Both models are validated using hydrographic data and current-meter observations in the core of the undercurrent in the northern CCS. In the linear model, variability in the predominantly equatorward wind stress along the U.S. West Coast produces episodic reversals to poleward flow over the northern CCS slope during summer. However, reproducing the persistence of the undercurrent during late summer requires additional incoming energy from sea level variability applied south of the region of the strongest wind forcing. The relative importance of the barotropic and baroclinic components of the modeled alongshore pressure gradient changes with latitude. In contrast to the southern and central portions of the CCS, the baroclinic component of the alongshore pressure gradient provides the primary poleward force at CUC depths over the northern CCS slope. At time scales from weeks to months, the alongshore pressure gradient force is primarily balanced by the Coriolis force associated with onshore flow.

Comments

This article, the Version of Record, originally appeared in Journal of Physical Oceanography in Volume 44, Issue 1 and can be found at this link.
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