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CATEGORIES:British Antarctic Survey
SUMMARY:Why do different climate models give different ans
 wers? An analysis of 21st century wind changes ove
 r the Amundsen Sea\, West Antarctica\, in the CMIP
 5 climate models - Dr. Thomas Bracegirdle
DTSTART;TZID=Europe/London:20140917T110000
DTEND;TZID=Europe/London:20140917T120000
UID:TALK54149AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/54149
DESCRIPTION:The influence of changes in winds over the Amundse
 n Sea has been shown to be a potentially key mecha
 nism in explaining rapid loss of ice from major gl
 aciers in West Antarctica\, which is having a sign
 ificant impact on global sea level. Here\, Coupled
  Model Intercomparison Project Phase 5 (CMIP5) cli
 mate model data are used to assess 21st century pr
 ojections in westerly winds over the Amundsen Sea 
 (UAS). For a given scenario of greenhouse gas conc
 entrations\, differences between different model p
 rojections can be split into contributions from in
 ternal climate variability and model uncertainty. 
 Model uncertainty comes from differences in the wa
 y different climate models are constructed and int
 ernal variability of the climate system is a furth
 er contributor. These sources of uncertainty are q
 uantified in projections following Representative 
 Concentration Pathway (RCP) 4.5 and RCP 8.5 scenar
 ios. \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\, as 
 a consequence of large internal climate variabilit
 y over the Amundsen Sea\, it takes until approxima
 tely 2030 (2065) for the RCP8.5 response to exceed
  one (two) standard deviation(s) of decadal intern
 al variability. \n\nIn all scenarios and seasons t
 he model uncertainty is large. However the present
 -day climatological zonal wind bias over the whole
  South Pacific\, which is important for tropical t
 eleconnections\, is strongly related to inter-mode
 l differences in projected change in UAS (more ski
 lful models show larger UAS increases). This relat
 ionship is significant in winter (r = -0.56) and s
 pring (r = -0.65)\, when the influence of the trop
 ics on the Amundsen Sea region is known to be impo
 rtant. Horizontal grid spacing and present day sea
  ice extent were not found to be significant sourc
 es of inter-model spread.\n\n[All welcome. If exte
 rnal to BAS\, please email the organiser in advanc
 e to gain access to the building.]
LOCATION:British Antarctic Survey\, Room 330B
CONTACT:Dr. Pranab Deb
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