Mean Lagrangian flow behavior on an open coast rip-channeled beach: A new perspective
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Authors
MacMahan, Jamie
Brown, Jeff
Brown, Jenna
Thornton, Ed
Reniers, Ad
Stanton, Timothy P.
Henriquez, Martijn
Gallagher, Edith
Morrison, Jon
Austin, Martin J.
Subjects
rip current
surf zone
Lagrangian
exchange
surf zone
Lagrangian
exchange
Advisors
Date of Issue
2010
Date
Publisher
Language
Abstract
The accepted view of rip currents is that they are an efficient mechanism for transporting material out of the
surf zone. Previous rip current campaigns on natural beaches have focused on Eulerian measurements with
sparse in situ pressure and current meter arrays. Here, for the first time, spatially synoptic estimates of rip
current flow patterns, vorticity, and Lagrangian transport behavior are measured in the field using a fleet of
30 position-tracking surfzone drifters during multiple rip current occurrences on an open coast beach in
Monterey, CA. Contrary to the classic view (Shepard et al., 1941), the rip current flow field consisted of semienclosed,
large-scale vortices that retained the drifters and resulted in a high number of Lagrangian
observations that are temporally and spatially repeated. Approximately 19% of the drifters deployed in the
rip currents exited the surf zone per hour, on average during the experiments. The observed surf zone
retention of drifters is consistent with measurements from different open coast beach rip current systems
(14% at meso-macrotidal Truc Vert, France and 16% at macrotidal Perranporth, United Kingdom). The threehour-
average cross-shore rip current velocity at Monterey was 30 cm/s with peak time-averaged velocities
of 40–60 cm/s depending on wave and tidal conditions. Drifters that episodically exited the surf zone were
transported approximately 2 surf zone widths offshore at ∼20 cm/s.
Type
Article
Description
Series/Report No
Department
Oceanography
Organization
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NPS Report Number
Sponsors
Funding
Format
Citation
Marine Geology 268 (2010) 1–15
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.