Fluxes and mixing of reacting biogeochemical scalars in a stratified shear layer

Biogeochemical scalars, representing many different species of phytoplankton, zooplankton, nutrients, etc., play an important role in marine ecosystems. Here we examine a simplified two-species system of generic phytoplankton and nutrient populations, modeled here as reacting scalars governed by advection-diffusion equations with added terms governing the biological reaction (nutrient uptake, phytoplankton death/remineralization). We perform direct numerical simulations of an idealized scenario in which initial layers of phytoplankton and nutrients are separated by an unstable stratified shear layer susceptible to either Kelvin-Helmholtz or Holmboe instability (canonical examples of overturning and scouring mixing events, respectively). We further vary the ratio of the reaction and flow timescales, considering cases of fast, slow, and comparable reaction rates. We find that turbulent advective fluxes show large oscillations during the evolution of the shear instabilities, associated wit..., , # Data from: Fluxes and mixing of reacting biogeochemical scalars in a stratified shear layer

Dataset DOI: [10.5061/dryad.n2z34tn99](10.5061/dryad.n2z34tn99)

## Description of the data and file structure

Data from two sets of fully three-dimensional stratified shear instability simulations (Kelvin-Helmholtz, Holmboe). Included are data directly from simulation output, as well as quantities calculated in post-processing.

### Files and variables

#### File: Re1000_Pr7_R1_SEP.mat, Re1000_Pr7_R3_SEP.mat

**Description:** These files contain horizontally averaged quantities for the Kelvin-Helmholtz case (R1) and Holmboe case (R3). These simulations included 13 scalar fields that are advanced in time along with the velocity and pressure. All variables involving the scalars have final dimension of size 13. Scalar 1 is buoyancy. Scalars 4, 8, and 12 are phytoplankton at low, intermediate, and high Dahmköhler number as seen in the paper. Scalars 2, 6, and 10 are phytoplankton at low, interme...,