Research

The ability of the oceans to regulate the climate system and mitigate its present and future changes depends on the strength and variability of its circulation and the intimate connection between dynamical and biogeochemical processes. By connecting water masses across the full depth of the ocean, the ocean circulation induces a large-scale redistribution of carbon, heat and nutrients that is key to the Earth’s climate and biogeochemical cycles.

My research focuses on:

The exchange rate of tracers between the surface and the ocean interior
The dynamics of the interior waters, which constitute the largest reservoirs for heat and carbon

The link between the global-scale ocean circulation and the distribution of tracers such as anthropogenic carbon and heat is shown in the image below. For example, the sinking of dense waters in the North Atlantic provides a pathway for the accumulation of anthropogenic carbon in this region. Similarly, the circumpolar circulation around Antarctica creates a barrier to the transfer of heat south; changes in such circulation have been causing an excessive heat flux to terminating glaciers in West Antarctica, which is causing ice shelf melting, with global implications for sea level rise.

(left) Schematic of the global Meridional Overturning Circulation, from Meredith, 2022. (middle) Inventory of anthropogenic carbon accumulated in the ocean interior up to 2013 (data from GLODAP gridded dataset). (right) Ocean heat content calculated from GLODAP gridded dataset.

PROJECTS

Ice-Ocean Interactions
Ongoing project: BRINE - Bellingshausen Region Ice-melt and Nutrient Exchanges (2024 - 2027)

Photo credit: Schmidt Ocean Institute/Alex Ingle

By using state-of-the-art autonomous vehicles, BRINE will explore:

The mechanisms driving the intrusion of warm Circumpolar Deep Water onto the continental shelf
The production rates and export pathways of freshwater from several ice shelves
The impacts of meltwater on biogeochemical cycles
The connectivity across West Antarctica, from the Peninsula to the Amundsen Sea

Funded by

Ocean Ventilation

The slideshow shows ventilation maps inferred using transient tracers (from Cimoli et al., 2023) and the process of collecting CFCs/SF6 samples from a CTD rosette. Photo credit: Laura Cimoli.

Waters are “ventilated” when they are in contact with the atmosphere, and so they can exchange properties - such as heat, carbon, and oxygen. When water becomes dense and sinks into the ocean interior (for example, in the North Atlantic and around Antarctica), it stops being ventilated and the clock of water “age” starts. Knowing the age of a water mass is important because it tells us how long it can store tracers in the ocean interior, for example, sequestering carbon for centuries or millennia.

In my work, I use transient tracers such as chlorofluorocarbons (CFCs) and sulfur-hexafluoride (SF6) to gain information about the ventilation rates and the age of water masses. CFCs and SF6 concentrations in the ocean interior are monitored thanks to international hydrographic programs, such as GO-SHIP.

Small-scale Ocean Turbulence

Turbulent mixing in the ocean interior is a very small-scale process (cm to metres), but it can alter water mass properties, oceanic heat content, biogeochemical processes and oceanic carbon storage through a variety of mechanisms.

In my research, I am interested in connecting the micro-scale physics of turbulence with its large-scale implications.

This remains a challenging process, as obtaining sufficient samples to quantify turbulent fluxes of water and tracers accurately is difficult, particularly at depth in the ocean water column. Furthermore, turbulence occurs at scales much smaller than the discretised grid cells of Earth System Models and thus must be parameterised. Hence, connecting such microphysics to regional and global physical and biogeochemical processes (scale of >100 km) remains a challenge.

Mixing is often enhanced near topography, where turbulence is generated by the interaction of the flow with the rough seafloor. The images show examples of inferred diapycnal (cross-density) velocity and of vorticity generated around seamounts.

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