Sack Lunch Seminar (SLS)

SLS: Ryan Abernathey - MIT
Date Time Location
November 30th, 2011 12:10pm-1:00pm 54-915
Ryan Abernathey, PAOC, MIT, presents "Global Estimates of Mesoscale Mixing Rates from Satellite Altimetry: Spatial Patterns and Implications for Ocean Models ."

Recent efforts to estimate mesoscale mixing rates have focused solely on the Southern Ocean. But eddy transport can be important elsewhere in the ocean, helping to determine, for example, the rate of uptake of anthropogenic CO2 and heat in the sup-tropical gyres. We attempt to measure mixing rates globally by simulating the transport of passive tracers using observed surface velocities from AVISO. One challenge is that, outside of the Southern Ocean, the complex geometry of the mean flows makes conventional effective-diffusivity diagnostics hard to apply. We present a comparison of different mixing diagnostics in a sector of the East Pacific and introduce a version of the Osborn-Cox diffusivity capable of quantifying irreversible mixing locally, rather than in a zonal or streamwise average. We then apply this diagnostic to create a global map of mesoscale mixing. We see that mean flows help modulate mixing rates globally and act to enhance diffusivities in the sub-equatorial region.