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SUMMARY:Southern Ocean overturning under past and future climate change - 
 Adele Morrison (Australian National University)
DTSTART:20120620T100000Z
DTEND:20120620T110000Z
UID:TALK38144@talks.cam.ac.uk
CONTACT:Povl Abrahamsen
DESCRIPTION:Understanding the response of the Southern Ocean overturning c
 irculation to changes in forcing is pivotal to projecting the future of th
 e Southern Ocean CO_2 sink and developing theories of glacial-interglacial
  outgassing. Using a series of idealised\, eddy-permitting to eddy-resolvi
 ng numerical simulations of the Southern Ocean\, we investigate the sensit
 ivity of the overturning to both wind stress and mid-latitude surface buoy
 ancy forcing.\n\nWe find that surface buoyancy forcing in the mid-latitude
 s is likely to play a significant role in setting the strength of the over
 turning circulation - providing support for the hypothesis that changes in
  upwelling during deglaciations may have been driven by changes in heat an
 d freshwater fluxes\, instead of or in addition to changes in wind stress.
 \n\nPrevious eddy-permitting studies have shown that the eddy field in the
  Southern Ocean offsets the impact of strengthening winds on both the over
 turning circulation and the Antarctic Circumpolar Current (ACC) transport.
  There is widespread belief that the sensitivities of the overturning and 
 ACC transport are dynamically linked\, with limitation of the ACC transpor
 t response implying limitation of the overturning response. We show that t
 here are significant differences between the sensitivities and resolution 
 dependence of the overturning and ACC transport\, indicating that they are
  controlled by distinct dynamical mechanisms. The modelled overturning is 
 significantly more sensitive to change than the ACC transport\, with the p
 ossible implication that the Southern Ocean overturning may increase in re
 sponse to future wind stress changes without measurable changes in the ACC
  transport. It is hypothesised that the dynamical distinction between the 
 zonal and meridional transport sensitivities is derived from the depth dep
 endence of the extent of cancellation between the Ekman and eddy-induced t
 ransports.\n
LOCATION:British Antarctic Survey\, Room 330B
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