| Summary: | Directional analysis has been used to study changes in the sub-polar climate of the mountainous and glacierised sub-Antarctic island of South Georgia (54-55°S, 36-38°W). Significantly for climate change studies, South Georgia lies in the Scotia Sea between polar and temperate latitudes, and approximately 1000 km northeast and downwind of the Antarctic Peninsula - one of the fastest-warming regions on Earth (Vaughan et al., 2001). South Georgia was chosen for directional analysis because its climate is substantially advected by predominantly westerly circulations, and because it has a long (since 1905) meteorological record from King Edward Point (KEP) on its eastern side. Additional shorter records from Bird Island at the northwest tip of South Georgia allow comparison between windward (Bird Island) and leeward (KEP) climate regimes. The variation of mountain barrier heights with direction from KEP allows climate changes to be studied under different amounts of orographic influence (from ~700 m to ~2200 m). Records of glacier advance and retreat provide further independent evidence of climate change for comparison with the meteorological record. Directional climate analysis is based on a series of monthly-mean pressure fields defining the orientation and strength of synoptic-scale air-mass advection over the Scotia Sea. These fields are used to define directional climatologies for six 30° sectors with bearings from 150-180° to 300-330°; these sectors encompass 99% of recorded months since 1905. The climatologies summarise the frequencies of air masses from each sector, and the accompanying temperatures and precipitation. The 6 sectors can be broadly associated with 4 air-mass types and source regions: (i) sectors 150-210° advect cold polar maritime air that originated over the Antarctic continent before passing over the Weddell Sea, (ii) sectors 210-270° advect warmer, more stable polar maritime air from the Bellingshausen Sea/Antarctic Peninsula region, (iii) sector 270-300° has warmer, drier returning polar ...
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