| Summary: | The Antarctic Peninsula, a relatively long, narrow extension of the Antarctic continent, defines a strong climatic gradient between the cold, dry continental regime to its south and the warm, moist maritime regime to its north. The potential for these contrasting climate regimes to shift in dominance from season to season and year to year creates a highly variable environment that is sensitive to climate perturbation. Consequently, long-term studies in the western Antarctic Peninsula (WAP) region, which is the location of the Palmer LTER (figure 9.1), provide the opportunity to observe how climate-driven variability in the physical environment is related to changes in the marine ecosystem (Ross et al. 1996; Smith et al. 1996; Smith et al. 1999). This is a sea ice–dominated ecosystem where the annual advance and retreat of the sea ice is a major physical determinant of spatial and temporal change in its structure and function, from total annual primary production to the breeding success and survival of seabirds. Mounting evidence suggests that the earth is experiencing a period of rapid climate change, and air temperature records from the last half century confirm a statistically significant warming trend within the WAP during the past half century (King 1994; King and Harangozo 1998; Marshall and King 1998; Ross et al. 1996; Sansom 1989; Smith et al. 1996; Stark 1994; van den Broeke 1998; Weatherly et al. 1991). Air temperature–sea ice linkages appear to be very strong in the WAP region (Jacka 1990; Jacka and Budd 1991; King 1994; Smith et al. 1996; Weatherly et al. 1991), and a statistically significant anticorrelation between air temperatures and sea ice extent has been observed for this region. Consistent with this strong coupling, sea ice extent in the WAP area has trended down during this period of satellite observations, and the sea ice season has shortened. In addition, both air temperature and sea ice have been shown to be significantly correlated with the Southern Oscillation Index (SOI), which suggests ...
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