How do ocean fronts structure pelagic ecosystems? A multi-sensor analysis in the Mozambique Channel.

Abstract

In my project, I analysed 8 months’ worth of Eulerian data (zooplankton, horizontal currents, temperature, salinity and pressure) from a multi-instrumented moored line deployed in 2022 in the central Mozambique Channel – a highly turbulent part of the world ocean prone to frontal activity. I synthesised this information with observations from satellites and from simulation outputs, to describe mesoscale and submesoscale ocean fronts in terms of the statistics of their occurrence, their depth profiles, and their interactions with living organisms. To do so, I defined a proxy for horizontal thermal gradients derived from mooring data, which I used to quantify frontal intensity at a length scale of tens of kilometres. I then verified prior results from model simulations regarding the depth profile of fronts. I show that in this dataset the subsurface gradient of temperature is poorly related to the SST gradient above it, a historically popular metric for fronts. Finally, I demonstrate clear impacts of enhanced thermal gradients on acoustic backscatter, used as a proxy for zooplankton.