Abstract:

Oceanic mesoscale flows span tens to hundreds of kilometers and evolve on timescales from days to weeks, accounting for most of the ocean kinetic energy in eddy form. Mesoscale eddies are dynamically important but computationally expensive to resolve in weather forecasting, seasonal prediction, and climate projection models, where they are commonly parameterized. However, how mesoscale eddies dissipate in the ocean is not well understood, thereby affecting the accuracy of ocean energy transfer and heat and nutrient transport by eddies in model simulations. A key to constrain dissipation is to evaluate the relative importance of energy pathways in simulation or to estimate dissipation rates from global observations. In this talk, I will show that western boundary regions may not represent the primary locations of eddy dissipation, contrary to previous suggestions of an eddy “graveyard.” Instead, idealized models indicate that energy dissipates near its generation regions, where eddy kinetic energy is high. We also develop a novel method that combines satellite and Argo observations to estimate bottom frictional dissipation rates and confirm this hypothesis. However, we find that bottom friction dissipates only approximately 20 % of the energy input and does not close the global energy budget, suggesting the need to examine additional energy pathways.