1. Linear Wind-Forced Beta Plumes with Application to the Hawaiian Lee Countercurrent*
- Author
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Nikolai Maximenko, Ali Belmadani, Niklas Schneider, Oleg Melnichenko, Emanuele Di Lorenzo, Julian P. McCreary, Ryo Furue, International Pacific Research Center (IPRC), School of Ocean and Earth Science and Technology (SOEST), University of Hawai‘i [Mānoa] (UHM)-University of Hawai‘i [Mānoa] (UHM), Universidad de Concepción - University of Concepcion [Chile], Department of Oceanography (SOEST), University of Hawai‘i [Mānoa] (UHM), and Georgia Institute of Technology [Atlanta]
- Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,010504 meteorology & atmospheric sciences ,010505 oceanography ,Baroclinity ,Rossby wave ,Zonal and meridional ,Geophysics ,Ocean general circulation model ,Forcing (mathematics) ,Regional Ocean Modeling System ,Oceanography ,[INFO.INFO-MO]Computer Science [cs]/Modeling and Simulation ,01 natural sciences ,Physics::Geophysics ,Plume ,13. Climate action ,Potential vorticity ,Climatology ,14. Life underwater ,ComputingMilieux_MISCELLANEOUS ,Physics::Atmospheric and Oceanic Physics ,Geology ,0105 earth and related environmental sciences - 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.
- Published
- 2013
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