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- Title
Linear Wind-Forced Beta Plumes with Application to the Hawaiian Lee Countercurrent*.
- Authors
Belmadani, Ali; Maximenko, Nikolai A.; Mccreary, Julian P.; Furue, Ryo; Melnichenko, Oleg V.; Schneider, Niklas; Lorenzo, Emanuele Di
- Abstract
Two numerical ocean models are used to study the baroclinic response to forcing by localized wind stress curl (i.e., a wind-forced β plume, which is a circulation cell developing to the west of the source region and composed of a set of zonal jets) with implications for the Hawaiian Lee Countercurrent (HLCC): an idealized primitive equation model [Regional Ocean Modeling System (ROMS)], and a global, eddy-resolving, general circulation model [Ocean General Circulation Model for the Earth Simulator (OFES)]. In addition, theoretical ideas inferred from a linear continuously stratified model are used to interpret results. In ROMS, vertical mixing preferentially damps higher-order vertical modes. The damping thickens the plume to the west of the forcing region, weakening the near-surface zonal jets and generating deeper zonal currents. The zonal damping scale increases monotonically with the meridional forcing scale, indicating a dominant role of vertical viscosity over diffusion, a consequence of the small forcing scale. In the OFES run forced by NCEP reanalysis winds, the HLCC has a vertical structure consistent with that of idealized β plumes simulated by ROMS, once the contribution of the North Equatorial Current (NEC) has been removed. Without this filtering, a deep HLCC branch appears artificially separated from the surface branch by the large-scale intermediate-depth NEC. The surface HLCC in two different OFES runs exhibits sensitivity to the meridional wind curl scale that agrees with the dynamics of a β plume in the presence of vertical viscosity. The existence of a deep HLCC extension is also suggested by velocities of Argo floats.
- Subjects
HAWAII; WIND pressure; COUNTERCURRENT processes; BAROCLINICITY; CIRCULATION models; EDDY viscosity; WATER currents
- Publication
Journal of Physical Oceanography, 2013, Vol 43, Issue 10, p2071
- ISSN
0022-3670
- Publication type
Article
- DOI
10.1175/JPO-D-12-0194.1