Speaker: Sean Chen (Imperial)
Title: From Surface to Abyss: Dynamical and Ecological Controls on Ocean Carbon Sequestration
Abstract: The deep ocean stores vast amounts of carbon and is often conceptualised as a slow, passively ventilated reservoir controlled primarily by overturning circulation. Yet growing observational and modelling evidence suggests that the abyss is far more dynamic. Deep-reaching mesoscale eddies, which frequently form within meandering surface current systems, and episodic benthic storms can resuspend sediments, redistribute fluid, tracers, and particles in the abyssal ocean, challenging the view of the deep ocean as a stable endpoint of carbon sequestration.
In this talk, I’ll first examine the dynamical processes that lead to the formation of deep-reaching eddies and their implications for tracer transport in the abyssal ocean. Observations and numerical simulations show that surface-intensified mesoscale eddies associated with strong currents, such as the Gulf Stream, can perturb bottom flows, generate benthic nepheloid layers, and enhance lateral particle transport, thereby modifying tracer distributions at depth. Next, I’ll explore the variability of supply of biogenic carbon to the interior ocean. Using a trait-based ecosystem model coupled to circulation, I’ll show preliminary estimates of carbon transience timescales in subpolar regions where sea-ice variability is expected to affect plankton community and particle export. Together, these perspectives highlight the complex vertical connectivity of the ocean carbon reservoir, linking transient physical variability in the abyss to ecological controls in the surface ocean.