Long-Term Ecological Research (Palmer LTER) on the Antarctic Marine Ecosystem 

Raymond C. Smith

Institute of Computational Earth System Science (ICESS), University of California Santa Barbara (UCSB), Santa Barbara, CA 93106
 

The Antarctic Peninsula 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.  Long-term studies in the western Antarctic Peninsula (WAP) region show that the WAP is a premier example of a climate-sensitive region experiencing major changes in species abundance and composition due to changes in range and distribution. 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.  The WAP region has experienced a statistically significant warming trend during the past half century.  In addition, a statistically significant anti-correlation 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 become shorter.  Further, both air temperature and sea ice have been shown to be significantly correlated with the Southern Oscillation Index (SOI), which suggests possible linkages between sea ice, cyclonic activity and global teleconnections.  Ecological responses to this climate variability are evident at all trophic levels, but are most clearly seen in a shift in the population size and distribution of penguin species with different affinities to sea ice.