This year, the 57th International Liège Colloquium on Ocean Dynamics will focus on submesoscale processing in the ocean.
The ocean is rich in processes that manifest at scales between hundreds of metres and tens of kilometres, small enough for the constraints of the Earth’s rotation and oceanic stratification to be overcome, but larger than that of three-dimensional turbulence. Where multiple forces in the ocean (Coriolis force versus advection and buoyancy versus shear stress) are of similar importance, we witness a wide range of dynamic instabilities that respond to surface forcing and boundary stresses, and interact with the mesoscale flow field, upper ocean turbulence, and near-inertial waves. These dynamics result in enhanced vertical velocities and mixing, as well as stratification, on time scales that range from a few days to the inertial period, and intersect with the timescales of internal waves and tides.
Their diagnosis is facilitated through advances in high-resolution autonomous, in-situ, and remotely-sensed observations, modelling, and theoretical advances. Their implications are wide-ranging, and include the transfer of energy across scales, lateral mixing and transport, restructuring of the upper ocean’s density and stratification, modulation of air-sea, ice-ocean, ocean-bathymetric interactions, the exchange of biogeochemical properties across the mixed layer base, subduction of surface water, and export of particulate organic carbon and oxygen from the surface mixed layer. The similarity of physical and biological time scales of phytoplankton growth heightens the relevance of submesoscale processes for the production and export of phytoplankton, and the structuring and diversity of oceanic ecosystems.
By revisiting this topic, 10 years after the 48th Liège Colloquium, this edition aims to assess the new developments in submesoscale research, across a range of oceanographic disciplines, including observational (in situ and remote sensing), modelling (dynamic and deep-learning based) and theoretical approaches. Topics that will be addressed include:
* Dynamics and impacts of frontal and mixed-layer instabilities, including, but not limited to baroclinic instability, symmetric instability, inertial instability, and ageostrophic anticyclonic instability.
* Interactions between surface boundary layer turbulence and submesoscale instabilities derived from large-eddy simulation and observations.
* Submesoscale air-sea interaction, including air-sea exchange at the submesoscales and its impact on boundary layer coupling.
* The role of submesoscales in vertical exchanges between the ocean surface layer and the ocean interior, including leading order processes, implications and progress towards parameterisation.
* Surface signatures of submesoscale dynamics from remotely sensed surface topography, roughness, and ocean color.
* Mesoscale-submesoscale interactions, energy cascades, cross-scale interaction.
* Physical-biological interactions and implications for biogeochemistry, productivity, export, and ecosystem structure and diversity.
* Lateral stirring and transport by submesoscale turbulence. Cross frontal exchange and implications for freshwater transport and ecosystem dynamics.
* Coastal and high latitude submesoscale dynamics, prediction improvement, coastal resilience.
* Submesoscales in the bottom boundary layer and interactions with topography.
* Frontal-wave interaction at submesoscales, internal wave modification and trapping, internal wave generation at submesoscales.
* Modelling issues related to multi-scale and multi-physics nature of the processes and in particular model nesting, unstructured grids, developments of new discretisation schemes and the use of machine learning.
* Submesoscales and climate including progress on parameterisations, the response of submesocales to long-term climate forcing and the influence of submesoscales on the equilibrium state of the ocean on longer timescales.