WEDNESDAY 12 October 2011 3pm in the Charnock Lecture Theatre
Turbulence, mixing, and blooms at ocean fronts
John Taylor
Department of Applied Mathematics and Theoretical Physics, University of Cambridge
ABSTRACT
Regions with large horizontal density gradients, or fronts, are ubiquitous features of the upper ocean. At locations where density surfaces outcrop from the ocean interior, fronts serve as conduits for transport of fluid properties, linking the deep ocean and the atmosphere. Although many fronts are under-resolved in global-scale ocean models, recent work has shown that fronts affect the large-scale circulation and biology of the ocean.
In this talk, I will describe results from several recent studies based on numerical simulations, which show that turbulent mixing can be strongly affected by fronts and is subject to two competing effects: turbulence is generated from the available potential energy associated with the front, but vertical mixing is inhibited by the stable stratification that develops as the front slumps. Using a simple phytoplankton model, we find that reduced vertical mixing at fronts can trigger blooms in light-limited conditions. These results help explain satellite observations of blooms at high-latitude fronts.