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SUMMARY:Ozone forcing of the coupled climate in the Southern Hemisphere - 
 David Ferreira (University of Reading)
DTSTART:20131204T110000Z
DTEND:20131204T120000Z
UID:TALK47264@talks.cam.ac.uk
CONTACT:Dr Dan Jones
DESCRIPTION:Interannual variability in the Southern Annular Mode (SAM) and
  sea ice covary such that an increase and southward shift in the surface w
 esterlies (a positive phase of the SAM) coincides with an expansion of the
  sea ice cover\, as seen in observations and models alike. Yet\, the sea i
 ce extent decreases in response to sustained\, multi-decadal positive SAM-
 like wind anomalies driven by 20th century ozone depletion in modeling stu
 dies. Why does sea ice appear to have opposite responses to SAM-like varia
 bility on interannual and multidecadal timescales? We demonstrate that the
  response of sea ice and the Southern Ocean to ozone depletion is a two ti
 mescale problem.\nThe two timescales emerge because the fast processes of 
 the surface mixed layer and the slow dynamics of the ocean interior drive 
 Sea Surface Temperature anomalies of opposite sign in response to a SAM pe
 rturbation.\n\nThis behavior is seen in two models (one with an idealized 
 geometry and another\, more sophisticated\, global climate model) although
  we find great uncertainties in the timescale of the transition from the f
 ast to the slow response. Processes that controls this transition are clar
 ified. Implications for the interpretation of observed decadal changes and
  future climate change in the Southern Hemisphere are discussed.
LOCATION:British Antarctic Survey\, Room 307
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