The climate of the tropical Pacific is characterised by large interannual variability as is the extratropical atmospheric circulation and climate of the South Pacific. Most of the tropical variability is associated with ENSO but evidence for ENSO teleconnections in the South Pacific and adjacent West Antarctica is limited. In this paper the first results are reported of a detailed study of ENSO teleconnections in the west Antarctic Peninsula (WAP) region of the South Pacific forming part of an investigation into the controls on observed austral winter (June-August) interannual climate variability in the region. Attention is paid to 1) relating anomalous winter atmospheric circulation behaviour to SST's in the central tropical Pacific (the Nino 3.4 region) and 2) relating winters of marked sea ice extent anomalies to the atmospheric circulation given that sea ice extent strongly modulates WAP winter air temperatures. A diagnostic approach is used that estimates the seasonal change in SST's in the Nino 3.4 region, a key area of ENSO interactions, and relates this quantity to the extratropical circulation. Routinely available historical Nino 3.4 SST data and southern hemisphere Australian Bureau of Meteorology numerical analyses for 1973-93 are used in the work.
Findings to date indicate that no two warm or cold ENSO events are the same in terms of the amount of winter seasonal SST cooling (the climatological norm) in the central Pacific. Cooling in warm events can be of similar magnitude to that in cold events. On the other hand, below-normal cooling, i.e. a disruption of the tropical annual cycle, is only seen during ENSO warm events. Variations in central Pacific winter season cooling appear to be associated with systematic changes in the extratropical atmospheric circulation through large parts of the South Pacific including the WAP. The circulation changes seen between years of below- and above-normal cooling also bear a close resemblance to gross changes identified in previous composite analyses of ENSO warm and cold events. Detailed work in progress also indicates that sea ice extent in the WAP is also highly sensitive to ENSO-related variations in the local atmospheric circulation variability, thus suggesting a link between WAP climate variability and that in the tropical Pacific. Results of the work will be reported and discussed.
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