Mesoscale to Submesoscale Transition in the California Current System. Part II: Frontal Processesстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 29 сентября 2021 г.
Аннотация:This is the second of three papers investigating the regime transition that occurs in numerical simulations
for an idealized, equilibrium, subtropical, eastern boundary, upwelling current system similar to the California
Current. The emergent upper-ocean submesoscale fronts are analyzed from phenomenological and
dynamical perspectives, using a combination of composite averaging and separation of distinctive subregions
of the flow. The initiating dynamical process for the transition is near-surface frontogenesis. The
frontal behavior is similar to both observed meteorological surface fronts and solutions of the approximate
dynamical model called surface dynamics (i.e., uniform interior potential vorticity q and diagnostic force
balance) in the intensification of surface density gradients and secondary circulations in response to a
mesoscale strain field. However, there are significant behavioral differences compared to the surfacedynamics
model. Wind stress acts on fronts through nonlinear Ekman transport and creation and destruction
of potential vorticity. The strain-induced frontogenesis is disrupted by vigorous submesoscale frontal
instabilities that in turn lead to secondary frontogenesis events, submesoscale vortices, and excitation of
even smaller-scale flows. Intermittent, submesoscale breakdown of geostrophic and gradient-wind force
balance occurs during the intense frontogenesis and frontal-instability events