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SUMMARY:Causes and effects of recent changes in Antarctic sea-ice transpor
 t - Alexander Haumann\, ETH Zurich
DTSTART:20150428T100000Z
DTEND:20150428T110000Z
UID:TALK56668@talks.cam.ac.uk
CONTACT:Dr Alexander Brearley
DESCRIPTION:Observations reveal significant changes in both Antarctic sea-
 ice cover and in the hydrography of the underlying Southern Ocean over the
  past decades. However\, our understanding on the processes that cause the
 se changes and the connection between the oceanic and sea-ice changes is s
 trongly limited by sparse observations and the failure of global models to
  reproduce these changes. Here\, we provide a synthesis of observation and
  model data to investigate recent changes in the sea-ice-ocean system that
  are driven by changes in atmospheric circulation. Based on observational 
 data\, we demonstrate that the recent sea-ice expansion is driven by an en
 hanced meridional transport of sea ice resulting from an intensified atmos
 pheric circulation. Combining these observational evidences with experimen
 ts with a global climate model (MPI-ESM)\, we infer an anthropogenic influ
 ence on the near-surface circulation and the enhanced sea-ice transport. W
 e estimate\, on the basis of a sea-ice mass budget from satellite data\, t
 hat this enhanced northward sea-ice transport caused up to two thirds of t
 he observed freshening of the Southern Ocean surface and intermediate wate
 rs in recent decades. Using an eddy-resolving regional ocean model (ROMS)\
 , we trace the influence of changes in the observation based sea-ice fluxe
 s on the Southern Ocean hydrography. First results suggest that these chan
 ges\, together with increased glacial melt fluxes from Antarctica\, can ex
 plain most of the recent stabilization of the high-latitude Southern Ocean
  surface waters. As a consequence\, our findings also imply that sea-ice p
 rocesses have a strong potential to alter the overturning circulation and\
 , thus\, the deep to surface ocean exchange of heat\, carbon\, and nutrien
 ts in the Southern Ocean.
LOCATION:British Antarctic Survey\, Room 307
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