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SUMMARY:Why do different climate models give different answers? An analysi
 s of 21st century wind changes over the Amundsen Sea\, West Antarctica\, i
 n the CMIP5 climate models - Dr. Thomas Bracegirdle
DTSTART:20140917T100000Z
DTEND:20140917T110000Z
UID:TALK54149@talks.cam.ac.uk
CONTACT:Dr. Pranab Deb
DESCRIPTION:The influence of changes in winds over the Amundsen Sea has be
 en shown to be a potentially key mechanism in explaining rapid loss of ice
  from major glaciers in West Antarctica\, which is having a significant im
 pact on global sea level. Here\, Coupled Model Intercomparison Project Pha
 se 5 (CMIP5) climate model data are used to assess 21st century projection
 s in westerly winds over the Amundsen Sea (UAS). For a given scenario of g
 reenhouse gas concentrations\, differences between different model project
 ions can be split into contributions from internal climate variability and
  model uncertainty. Model uncertainty comes from differences in the way di
 fferent climate models are constructed and internal variability of the cli
 mate system is a further contributor. These sources of uncertainty are qua
 ntified in projections following Representative Concentration Pathway (RCP
 ) 4.5 and RCP 8.5 scenarios. \n\nFor the decade 2090-2099 the CMIP5 models
  show ensemble mean 21st century changes in annual mean UAS of 0.3 and 0.7
  m s-1 following the RCP4.5 and RCP8.5 scenarios respectively. However\, a
 s a consequence of large internal climate variability over the Amundsen Se
 a\, it takes until approximately 2030 (2065) for the RCP8.5 response to ex
 ceed one (two) standard deviation(s) of decadal internal variability. \n\n
 In all scenarios and seasons the model uncertainty is large. However the p
 resent-day climatological zonal wind bias over the whole South Pacific\, w
 hich is important for tropical teleconnections\, is strongly related to in
 ter-model differences in projected change in UAS (more skilful models show
  larger UAS increases). This relationship is significant in winter (r = -0
 .56) and spring (r = -0.65)\, when the influence of the tropics on the Amu
 ndsen Sea region is known to be important. Horizontal grid spacing and pre
 sent day sea ice extent were not found to be significant sources of inter-
 model spread.\n\n[All welcome. If external to BAS\, please email the organ
 iser in advance to gain access to the building.]
LOCATION:British Antarctic Survey\, Room 330B
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