Recently the dynamics of flows beneath ice cover has garnered much interest in the environmental fluid dynamics community. Of particular importance is understanding how heat introduced via solar radiation is transported within a body of cold fresh water (characteristic temperatures are below the temperature of maximum density), and how a subsurface current affects this process. In this study we present high-resolution numerical simulations of the interaction between cold water convection and a parallel shear flow. The results of this paper show that for a sufficiently strong shear current, the growth phase of instabilities generated by volumetric thermal forcing (which represents solar radiation) is nearly two-dimensional and that the transition to more vigorous three-dimensional motion is initialized by baroclinic production of vorticity by convective instabilities followed by a rapid increase in streamwise vorticity generated by vortex tilting and stretching. We describe how this process is modified by differences in shear strength and thermal forcing attenuation length.

• Received 4 October 2021
• Accepted 5 January 2022

DOI:https://doi.org/10.1103/PhysRevFluids.7.023501