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SUMMARY:Drivers of Antarctic High Temperature Extremes Revealed using Self
  Organised Mapping - Max Harvey (University of Cambridge)
DTSTART:20250619T130000Z
DTEND:20250619T140000Z
UID:TALK233608@talks.cam.ac.uk
CONTACT:Thomas Caton Harrison
DESCRIPTION:Extreme temperatures in the Antarctic Peninsula (AP) arise fro
 m complex synoptic patterns that exhibit non-linear relationships with lar
 ge-scale climate drivers such as ENSO\, the Interdecadal Pacific Oscillati
 on (IPO)\, and the Southern Annular Mode (SAM). These events are closely a
 ssociated with variations in surface air temperature and wind patterns\, w
 hich in turn influence sea ice extent and regional climate feedbacks. Trad
 itional approaches to analysing the synoptic conditions behind extreme hig
 h daily mean temperatures have relied heavily on composite analysis\, whic
 h can obscure more intricate or compound structures. This study presents a
  framework for applying Self-Organizing Maps (SOMs) to mean sea level pres
 sure (MSLP) fields to uncover new complex\, non-linear synoptic modes. By 
 relaxing the orthogonality constraint inherent in Empirical Orthogonal Fun
 ction (EOF) analysis\, SOMs reveal additional physically meaningful modes 
 that significantly contribute to extreme heat events in the AP. In particu
 lar\, this analysis identifies a quasi-stationary Rossby wave mode origina
 ting from the Australian Southern Ocean\, whose occurrence decreases follo
 wing the IPO phase reversal in the late 1990s. This Rossby wave pattern is
  linked to anomalously warm sea surface temperatures (SSTs) off the coast 
 of Australia that are favoured during the positive IPO phase. These anomal
 ous SSTs amplify transient Rossby waves\, passing over the region and enha
 nce their downstream effect. Waveguiding by the Polar front Jet (PFJ) enab
 les constructive interference between this quasi-stationary wave train and
  existing climatological features such as the Bellingshausen Sea Low (BSL)
  and Atlantic anticyclonic blocking\, leading to an increased likelihood o
 f extreme high daily mean temperature events occurring in the AP region. T
 his occurrence of the quasi-stationary Rossby wave mode\, is shown to be d
 irectly controlled by the phase and strength of the IPO\, exhibiting decad
 al and inter-decadal length variation in its activation.
LOCATION:BAS Seminar Room 330b and Zoom
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