Weekly CASPO Seminar: join us on Zoom every Wednesday at 3:30 pm to hear about the latest and greatest in Climate, Atmospheric Sciences, and Physical Oceanography!
We're very excited to ring in 2021 and the winter quarter this Wednesday, January 6th at 3:30pm, with our very own Professor Matthew Alford presenting the following talk:
Revisiting near-inertial waves: mixed-layer deepening and local/remote generation
Near-inertial motions are ubiquitous in the ocean, and of known importance in mixing the deep sea as well as deepening the mixed layer. Their ability to deepen the mixed layer rapidly during resonant wind forcing causes i) slab-model representations of them to overestimate their kinetic energy and work and ii) the energy available for propagating waves to be reduced significantly by the turbulence required to do the deepening. I this talk I revisit mixed-layer models of Pollard, Rhines and Thompson (1973) and KPP simulations (Crawford and Large 1996) to reconcile these ideas, and also compute global maps of the fraction “q” of the wind work that is dissipated locally. It’s shown that shallow mixed layers may expend half or more of the wind work in turbulent deepening of the mixed layer, while deep mixed layers mix only little. The “modified wind work,” or wind work minus turbulent production may thus be significantly less (but with large uncertainty) than previously thought, possibly lowering near-inertial waves in importance relative to the internal tides. Along the way, potential energy changes due to wind and convection are computed from climatology and Argo profiles and compared - obtaining a global constraint on entrainment fluxes at the mixed-layer base. These results urgently call for more direct observations of mixed-layer deepening and the transition layer during resonant forcing conditions.
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