Presenter: Mikhail Schee (University of Toronto)

Description:
The Arctic Ocean contains a warm layer originating from the Atlantic Ocean below a pycnocline which has a thermohaline staircase structure that inhibits vertical mixing. If the heat from the Atlantic layer were to rise to the surface, the rate of sea ice loss would increase dramatically. Wind stress and ice floes generate internal waves which can propagate downwards and cause vertical mixing. As sea ice cover in the Arctic continues to decline, it will be important to predict how these changing internal waves transport energy through such stratification profiles. Here, we investigate how density staircases enhance or limit downward near-inertial wave propagation. We use direct numerical simulations to solve the Boussinesq equations of motion using spectral methods. We simulate the propagation of internal waves through a vertically stratified fluid which includes one or more steps (i.e., mixed layers). We numerically reproduce the results of laboratory experiments showing transmission and reflection of internal waves from one or two mixed layers. We then extend our parameter regime to simulate the propagation of internal waves through a more realistic stratification profile, tending toward that of the Arctic pycnocline.