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SUMMARY:Antarctic extreme seasons under 20th and 21st century climate chan
 ge - Tom Bracegirdle (BAS)
DTSTART:20250227T110000Z
DTEND:20250227T120000Z
UID:TALK227509@talks.cam.ac.uk
CONTACT:Thomas Caton Harrison
DESCRIPTION:Persistent extremes atmospheric conditions over a season (clas
 sed as climate extremes by the IPCC) are of particular importance as they 
 can produce accumulated effects of greater impact than a single weather ev
 ent. For example\, the breakup of the Larsen B Ice Shelf occurred followin
 g a summer of persistent surface melt in 2002. From an ecosystem perspecti
 ve\, penguin breeding can be severely affected by persistent adverse condi
 tions over a season. Our knowledge of the behaviour of extremes under clim
 ate change is poor due to both limited observations and a lack of necessar
 y climate model simulations.\n\nIn this talk I will present the first mult
 i-variate overview of the evolution of extreme seasons over Antarctica and
  the Southern Ocean during the 20th and 21st centuries\, focussing on surf
 ace-air temperature\, precipitation and near-surface wind. This has been m
 ade possible by the increasing availability of ‘large ensembles’ of cl
 imate model simulations\, which involve running climate models many times 
 and can be used to assess the behaviour of rare extreme events under clima
 te change. Specifically\, in this study available large ensemble datasets 
 in the Coupled Model Intercomparison Phase 6 (CMIP6) archive were used to 
 provide following medium-to-high radiative forcing scenarios.\n\nThe resul
 ts show significant differences between simulated changes in background me
 an climate and changes in low (10th percentile) and high (90th percentile)
  extreme seasons. Regional winter warming is most pronounced for cold extr
 emes. In summer\, there are more pronounced increases in high extremes in 
 precipitation and westerly wind during the ozone hole formation period (la
 te 20th century)\, affecting coastal regions and\, in particular\, the Ant
 arctic Peninsula. At midlatitudes\, there is a reduction in the range of s
 ummer season wind extremes. Suggested mechanisms for these differences wil
 l be presented\, in particular relating to sea ice retreat and westerly je
 t position.
LOCATION:BAS Seminar Room 1 and Zoom
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