Near-inertial waves and turbulence driven by the growth of swell

(Wagner, Gregory L. and Chini, Gregory P. and Ramadhan, Ali and Gallet, Basile and Ferrari, Raffaele), Journal of Physical Oceanography, no. 2, pp. pages, 2021.


Between 5 and 25% of the total momentum transferred between the atmosphere and ocean is transmitted via the growth of long surface gravity waves called `swell’. In this paper, we use large eddy simulations to show that swell-transmitted momentum excites near-inertial waves and drives turbulent mixing that deepens a rotating, stratified, turbulent ocean surface boundary layer. We find that swell-transmitted currents are less effective at producing turbulence and mixing the boundary layer than currents driven by an effective surface stress. Overall, however, the differences between swell-driven and surface-stress-driven boundary layers are relatively minor. In consequence, our results corroborate assumptions made in Earth system models that neglect the vertical structure of swell-transmitted momentum fluxes and instead parameterize all air-sea momentum transfer processes with an effective surface stress.

doi = 10.1175/jpo-d-20-0178.1

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