Submesoscale frontal dynamics

Ocean fronts develop where waters with different temperature and salinity meet. Fronts, which include large-scale current systems such as the Gulf Stream and smaller ephemeral features, are ubiquitous in the upper ocean. Fronts are extremely energetic and dynamic environments with important influences on the local biology and the global carbon cycle. By definition, fronts are places where density surfaces, or isopycnals, outcrop from the ocean's stratified interior. Recent evidence indicates that these outcropping isopycnals provide a pathway that allows direct and rapid transfer of important tracers such as dissolved carbon, oxygen, and nutrients between the ocean surface and interior. The rate of exchange of water between the ocean surface and interior in turn affects the ability of the ocean to mediate changes in the earth's climate. Despite their global significance, many fundamental questions about fronts remain unanswered. Why are fronts often much more biologically productive than surrounding areas? How do fronts modify the intensity of turbulent mixing? What physical processes balance the convergent surface flow at fronts, ultimately determining their width and strength?

For this project, the student will use a combination of numerical simulations, mathematical theory, and field data to answer these important problems. Based on available hydrographic sections taken across several ocean fronts, we will identify important parameters including the density contrast, mixed layer depth, and vertical extent of the front. We will then build and analyse a suite of numerical simulations to study the evolution of fronts in different parameter ranges. A linear stability analysis will allow us to identify the disturbances that eventually develop into frontal eddies. Finally, we will compare our results with existing and new observational data. We will adapt the approach based on the results and the interests of the student and the project will have scope for open exploration of the topic.