The International Antarctic Scientific Expedition (ITASE) is a nineteen-nation strong, multi-disciplinary research program endorsed by the Scientific Committee on Antarctic Research (SCAR) and the International Geosphere Biosphere Program (IGBP) (Mayewski and Goodwin, 1997). It is designed to   reconstruct the recent climate history of Antarctica through ice coring and related observations along a network of extensive intra-continental traverses (Figure 1).

West Antarctica and Phase One of US ITASE
The first four years of the United States contribution to ITASE (1999-2003) have focused on a series of traverses extending over West Antarctica (Figure 1). West Antarctica is of particular importance because this region is strongly linked with climate variability at lower latitudes and therefore offers an opportunity for understanding regional to global scale climate variability.

Figure 1 - ITASE traverse routes – completed (solid), proposed (dashed) superimposed on RADARSAT imagery (Jezek et al., 2002).

In particular, the El Niño-Southern Oscillation (ENSO)    phenomenon  in  the  tropical  and  the

subtropical Pacific Ocean is known to impact West Antarctica from the Ross Sea to the Weddell Sea as part of the Pacific-South American (PSA) teleconnection pattern. The “ENSO teleconnection” exhibits substantial seasonal to decadal scale variability. The suite of sub-annually resolved climate records retrieved by US ITASE will allow climate variability over West Antarctica to be established on inter-annual   through   centennial  timescales. In combination with deep ice cores – some already completed, others to be drilled in the near future – US ITASE will also contribute to the understanding of climate on millennial time scales. Information about climate variability in the middle and high latitudes of the Southern Hemisphere is obtained, through calibrations developed between US ITASE ice core records and direct atmospheric observations collected over the last 45 years. A primary goal of the calibration work is to document variation in the ENSO teleconnection and to better understand the relationship between global scale variability and regional Antarctic climate. This will establish a record of natural fluctuations of ENSO frequency and amplitude prior to the beginning of anthropogenic influence on climate, and will help in determining whether the frequency of El Niños changed in the late 20th century relative to earlier periods. This is a question of great importance because climate models indicate El Niño frequency may be enhanced due to global warming. Another important goal is to better understand the Antarctic Oscillation (AAO) (also known as the Southern Annular mode or the high latitude mode). It is the dominant atmospheric teleconnection pattern in West Antarctica after ENSO, and may be the most important for the rest of the continent. Recent changes in the AAO have been related to anthropogenic ozone destruction (Thompson and Solomon, 2002), but the existing record is too short to establish whether those changes are unprecedented. ITASE research will contribute important data to resolving this question.