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Influence of varying upper ocean stratification on coastal near‐inertial currents
Author(s) -
Kim Sung Yong,
Kurapov Alexander L.,
Kosro P. Michael
Publication year - 2015
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2015jc011153
Subject(s) - stratification (seeds) , inertial wave , shore , geology , submarine pipeline , mixed layer , wind stress , surface layer , amplitude , oceanography , environmental science , wave propagation , layer (electronics) , physics , seed dormancy , mechanical wave , longitudinal wave , botany , germination , chemistry , organic chemistry , quantum mechanics , dormancy , biology
The influence of varying horizontal and vertical stratification in the upper layer ( O ( 10 ) m) associated with riverine waters and seasonal atmospheric fluxes on coastal near‐inertial currents is investigated with remotely sensed and in situ observations of surface and subsurface currents and realistic numerical model outputs off the coast of Oregon. Based on numerical simulations with and without the Columbia River (CR) during summer, the directly wind‐forced near‐inertial surface currents are enhanced by 30%–60% when the near‐surface layer has a stratified condition due to riverine water inputs from the CR. Comparing model results without the CR for summer and winter conditions indicates that the directly wind‐forced near‐inertial surface current response to a unit wind forcing during summer are 20%–70% stronger than those during winter depending on the cross‐shore location, which is in contrast to the seasonal patterns of both mixed‐layer depth and amplitudes of near‐inertial currents. The model simulations are used to examine aspects of coastal inhibition of near‐inertial currents, manifested in their spatial coherence in the cross‐shore direction, where the phase propagates upward over the continental shelf, bounces at the coast, and continues increasing upward offshore (toward surface) and then downward offshore at the surface, with magnitudes and length scales in the near‐surface layer increasing offshore. This pattern exhibits a particularly well‐organized structure during winter. Similarly, the raypaths of clockwise near‐inertial internal waves are consistent with the phase propagation of coherence, showing the influence of upper layer stratification and coastal inhibition.