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SUMMARY:Vorticity Balance of the Antarctic Circumpolar Current in Drake Pa
 ssage - Dr. Yvonne Firing\, National Oceaongraphy Centre Southampton
DTSTART:20141203T140000Z
DTEND:20141203T150000Z
UID:TALK55384@talks.cam.ac.uk
CONTACT:Dr Alexander Brearley
DESCRIPTION:The nonlinear vorticity balance of the Antarctic Circumpolar C
 urrent in Drake Passage is examined using observations and the eddy-permit
 ting Southern Ocean State Estimate (SOSE).  Four years of near-bottom curr
 ents\, bottom pressures\, and bottom-surface round-trip sound travel time 
 were collected by Current and Pressure-recording Inverted Echo Sounders (C
 PIES) deployed in a line across Drake Passage and in a two-dimensional arr
 ay in the Polar Frontal Zone (PFZ) downstream of the Shackleton Fracture Z
 one (SFZ) as part of the cDrake experiment.  Empirical relationships based
  on historical hydrography are used to convert travel time data to barocli
 nic streamfunction\, which can be referenced by measured bottom pressures 
 and currents.  \n\nNonlinear relative vorticity advection dominates the ob
 served time-varying and mean PFZ vorticity budgets\, and approximately one
  third of the time-averaged relative vorticity advection in this region is
  attributable to transient eddies.  In the model time-mean vorticity budge
 t terms dependent on model grid resolution\, including parameterized eddy 
 diffusivity\, are significant\, and at spatial scales of 100s of km planet
 ary vorticity advection becomes first order.  Depth-integrated relative vo
 rticity advection in the cDrake array in the PFZ is negatively correlated 
 with the observed bottom pressure torque\, which is driven by strong near-
 bottom currents.  Much larger and highly time-variable bottom pressure tor
 ques inferred over the northern and southern continental slopes are produc
 ed by moderate currents flowing slightly across steep topographic slopes. 
  SOSE also exhibits strong bottom pressure torques over these topographic 
 features\, positively correlated with depth-integrated relative vorticity 
 advection and balanced by depth-integrated planetary vorticity advection a
 nd model grid resolution terms. 
LOCATION:British Antarctic Survey\, Room 330B
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