Drivers of Antarctic High Temperature Extremes Revealed using Self Organised Mapping

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• Max Harvey (University of Cambridge)
• Thursday 19 June 2025, 14:00-15:00
• BAS Seminar Room 330b and Zoom.

If you have a question about this talk, please contact Thomas Caton Harrison.

Extreme temperatures in the Antarctic Peninsula (AP) arise from complex synoptic patterns that exhibit non-linear relationships with large-scale climate drivers such as ENSO , the Interdecadal Pacific Oscillation (IPO), and the Southern Annular Mode (SAM). These events are closely associated with variations in surface air temperature and wind patterns, which in turn influence sea ice extent and regional climate feedbacks. Traditional approaches to analysing the synoptic conditions behind extreme high daily mean temperatures have relied heavily on composite analysis, which can obscure more intricate or compound structures. This study presents a framework for applying Self-Organizing Maps (SOMs) to mean sea level pressure (MSLP) fields to uncover new complex, non-linear synoptic modes. By relaxing the orthogonality constraint inherent in Empirical Orthogonal Function (EOF) analysis, SOMs reveal additional physically meaningful modes that significantly contribute to extreme heat events in the AP. In particular, this analysis identifies a quasi-stationary Rossby wave mode originating from the Australian Southern Ocean, whose occurrence decreases following 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 anomalous SSTs amplify transient Rossby waves, passing over the region and enhance their downstream effect. Waveguiding by the Polar front Jet (PFJ) enables 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 of extreme high daily mean temperature events occurring in the AP region. This occurrence of the quasi-stationary Rossby wave mode, is shown to be directly controlled by the phase and strength of the IPO , exhibiting decadal and inter-decadal length variation in its activation.

This talk is part of the BAS Atmosphere, Ice and Climate Seminars series.

This talk is included in these lists:

• BAS Atmosphere, Ice and Climate Seminars
• BAS Seminar Room 330b and Zoom

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