Enso Effects on Temperature and Precipitation of the Patagonian-Andean Region: Implications for Biogeography

This study documents instabilities in the relationship between El Niño-Southern Oscillation (ENSO) and climate of the Patagonian-Andean region at spatial and temporal scales directly relevant to biogeographical research. Four temperature and four precipitation regions located south of 38°S were described using homogeneous climate records that were significantly correlated. Correlation function analysis evaluated the response of seasonal temperature and precipitation for each region relative to two indices of ENSO, the Southern Oscillation Index (SOI) and tropical Pacific sea surface temperatures (SSTs). Statistically significant correlations were observed for each region, although relationships varied among regions. Climatic responses to El Niño events were deduced from these relationships. The 30-year moving correlations of temperature and precipitation against SOI and SST showed substantial temporal instability of the ENSO-climate relationships during this century. These instabilities are explained by documented, multi-decadal variations in ENSO, the southeast Pacific anticyclone, and mean sea-level pressure (SLP) in the southern Atlantic Ocean. Despite significant relationships between ENSO and climate for particular regions and periods, we did not find that such relationships were consistent in space or time. ENSO-climate relationships often are useful for understanding temporal variability in ecological processes, but temporal instability in these relationships limits their predictive ability. [Key words: Argentina, Chile, climate variation, correlation analyses, El Niño, South America, southern oscillation.]