Environmental Science and Engineering Seminar

Ocean eddies (with a size of 100-300km), ubiquitous in satellite observations, are known to represent  about 60-80% of the total ocean kinetic energy.  Recent studies have pointed out the unexpected role of smaller oceanic structures (with 1km-50km scales) to generate and sustain these eddies. The interpretation proposed invokes the instability resulting from the interaction between surface and interior modes.

In this study we show instead, using a new high-resolution simulation of the realistic North Pacific Ocean, that ocean eddies are sustained by a more energetic and different process involving small-scale mixed-layer instabilities set up by large-scale atmospheric forcing in winter. This leads to a seasonal evolution of the eddy kinetic energy in a very large part of this ocean (including the Kuroshio and the subtropical gyre), with an amplitude varying by a factor almost equal to two. Perspectives in terms of the impacts on climate dynamics and future satellite observational systems are briefly discussed.