A Dynamical Model of the Beaufort Gyre: A Balance between Ekman Pumping and Eddy Fluxes Jiayan Yang & Andrey Proshutinsky Woods Hole Oceanographic Institution.

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A Dynamical Model of the Beaufort Gyre: A Balance between Ekman Pumping and Eddy Fluxes Jiayan Yang & Andrey Proshutinsky Woods Hole Oceanographic Institution 2 nd FAMOS Workshop, Woods Hole, MA, Oct , 2013

Schematic of Arctic Ocean Circulation Beaufort Gyre (

wind Western Boundary Current y z Ekman Transport Ekman pumping Sverdrup Transport The 0th order dynamics of a mid-latitude gyre: BUT in the Arctic Ocean, there are some major uncertainties about the Beaufort Gyre dynamics: - does the Sverdrup balance work? - what is the removal mechanism for the low-salinity water-mass that has been accumulated by the Ekman pumping? - how the gyre is closed without a western boundary (in terms of PV, volume and momentum fluxes)

Beaufort Gyre Observing System (BGOS) present

Summer freshwater content in the BG region based on the Beaufort Gyre Observing System data. During , the Freshwater content in the region has increased by 5200 cubic kilometers.

(u 1,v 1 ) (u 2,v 2 ) A two-layer model used by Yang and Pratt (2013) for Nordic Seas Overflow

Forcing data: ice concentration  (NASA/GSFC), and ice velocity (NSIDC) and surface wind stress (NCEP-NCAR) The model is forced by daily surface stress

The model simulates the rapid increase of the FW from 2003 to 2008; The upward trend seems to stop (or slow down) after 2008; Would the upward trend start again if the forcing changes? Eddies seemed to be more abundant after What role did eddies play? And more fundamentally, what is the 0 th order dynamical balance that maintains the Beaufort Gyre?

North Pole Canada Basin Eddy fluxes

Inserting a western boundary value of  at 45N

Mean vorticity convergence of wind-stress curl frictional torque Advection eddy vorticity flux A1 A2 A3 A4 An Active role of eddies in the Arctic Ocean: Coarse resolutions: Eddy-resolving runs: (balance between surface and bottom Ekman layers)

Summary: (1)The main dynamical balance that maintains the Beaufort Gyre is between the surface wind-stress curl (Ekman pumping) and eddy PV fluxes; (2) Eddies also play a leading role in volume-transport balance, and they are likely the main removal mechanism for the accumulated fresh water in BG ; (3) Eddies are formed when the BG intensifies, the isopycnal steepens and becomes baroclinically unstable. (4) Eddy fluxes may have slowed down the upward trend in FW accumulation in BG.