Fluxes and mixing of reacting biogeochemical scalars in stratified shear layers

Refreshments will be served at 3:30 in MATX 1100.

To be held at MATX 1100 and on Zoom: https://ubc.zoom.us/j/68285564037?pwd=R2ZpLy9uc2pUYldHT3laK3orakg0dz09
Meeting ID: 682 8556 4037
Passcode: 636252

Turbulent mixing is a key physical process in the ocean, impacting the distributions of momentum, heat, salt, and other important tracers. The latter includes biogeochemical (BGC) scalars, representing many different species of plankton and nutrients that play an important role in marine ecosystems; representing their fluxes is a major challenge in earth system models. A common approach in studying ocean mixing is to represent individual mixing events in terms of canonical stratified shear instabilities and use the corresponding turbulent fluxes as the basis for larger-scale mixing parameterizations. However, the case of BGC scalars introduces the possibility of reactions between the different constituents, which can modify their overall transport. This raises an important question: how are these turbulent fluxes modified in the case of reacting scalars?

In this talk, I will first describe the canonical flow instabilities and give an overview of their mixing behaviour. I will then show the results of recent direct numerical simulations in which these instabilities are coupled to an idealized reaction-advection-diffusion model for phytoplankton-nutrient interactions. Along with this, I will show how existing analyses for stratified flows can be extended to include the effects of reacting scalars, allowing us to quantify the resulting mixing behaviour. With these simulations, I will explore how the type of instability and the reaction timescale impact the resulting turbulent fluxes.