Eddy Mixing in the Ocean (Ocean Mesoscale Eddies)

The ocean circulation is dominated by geostrophic eddies, i.e. cyclones and anticyclones with radii of 10-100 kilometers. These eddies are the ocean equivalent of the storms we experience in the atmosphere as weather. Eddies play an important role in the transport of heat, carbon and other climatically important tracers across the oceans. The group is very active in this research area and we develop theories for the physics of ocean eddies, their role in climate, and their representation in numerical models used for climate studies. We are also involved in the DIMES observational campaign aimed at measuring eddy mixing in the Southern Ocean, and the SWOT altimetry mission that will provide global maps of the surface eddy field at unprecedented resolution.

The ocean is a critical regulator of the Earth’s climate over timescales of decades to millennia. Through its circulation and biological activity, heat, carbon and other climatically important tracers are distributed around the globe and stored in its interior. Notably, since man started emitting carbon dioxide (CO2) into the atmosphere, the ocean appears to have been the main sink for CO2. In the quest to observe, understand and model the ocean, however, we are confronted by a major challenge: the ubiquity of oceanic turbulence on space scales of hundreds of meters to hundreds of kilometers and time-scales of days. These “mesoscale” motions are vividly illustrated in both models and data. The mesoscale is so energetic (it contains 90% of the ocean’s kinetic energy) that it often masks the mean circulation, which only emerges after averaging in space and time. Physically the mesoscale markedly enhances the rate at which the ocean mixes tracers both in the horizontal and the vertical. It acts as the "bridge" between energy input on the large scale and dissipation on microscales, although the detailed pathways remain uncertain.

Our research focuses on understanding the role of ocean turbulence in climate and developing parameterization to represent ocean turbulence in climate models.