Submesoscale Baroclinic Instability in the Bottom Boundary Layer
Weakly stratified layers over sloping topography can support a submesoscale baroclinic instability mode, a bottom boundary layer counterpart to surface mixed layer instabilities. The instability results from the release of available potential energy, which can be generated because of the observed bottom intensification of turbulent mixing in the deep ocean, or the Ekman adjustment of a current on a slope. Linear stability analysis suggests that the growth rates of bottom boundary layer baroclinic instabilities can be comparable to those of the surface mixed layer mode and are relatively insensitive to topographic slope angle, implying the instability is robust and potentially active in many areas of the global oceans. The solutions of two separate one-dimensional theories of the bottom boundary layer are both demonstrated to be linearly unstable to baroclinic instability, and results from an example nonlinear simulation are shown. Implications of these findings for understanding bottom boundary layer dynamics and processes are discussed.
Additional Information© 2018 American Meteorological Society. Received: 14 December 2017; Final Form: 21 March 2018; Published Online: 23 October 2018. The authors thank the contributors to the Dedalus Project (www.dedalus-project.org) and GOTM (www.gotm.net), both of which were extremely useful for the analyses in this paper. Authors JOW and LNT were supported during this work by NSF Grant OCE-1459677. Comments from three anonymous reviewers are also gratefully acknowledged.
Published - jpo-d-17-0264.1.pdf