Precipitationsensitive Treering Records

Relationships between SSTs in the equatorial Pacific and precipitation anomalies in central Chile (30°-35°S) have been reported by several authors (Quinn and Neal, 1983; Aceituno, 1988; Rutlland and Fuenzalida, 1991; Aceituno and Montecinos, 1996). Positive rainfall anomalies in central Chile are associated with warmer SSTs in the tropical Pacific. Conversely, cold SSTs correspond quite closely to dry conditions. Tree growth in central Chile is influenced largely by year-to-year variations in precipitation (LaMarche, 1975; Boninsegna, 1988; Villalba, 1990, 1995). Aring-width chronology for ciprés (Austrocedrus chilensis D. Don) at El Asiento (32°40' S), which represents the northernmost extent of this species in central Chile, was used by Boninsegna (1988) to develop a quantitative reconstruction of winter precipitation for Santiago, Chile, during the interval A.D. 1220-1972. Recently, the site was revisited, and the new cores were merged with the original data col-

FIGURE 4 Comparison of the amplitudes resulting from principal components (PCs) analyses of temperature-sensitive chronologies from northern Patagonia (thick line) and coastal Alaska (thin line) during the past400years. The northern Patagonia record is the leading PC resulting from an analysis of three upper elevation chronologies (year t and t + 1), whereas the coastal Alaska record is the leading PC from seven coastal chronologies (year t and t + 1). The Patagonia and Alaska records are significantly correlated at the 99.99% confidence level.

FIGURE 4 Comparison of the amplitudes resulting from principal components (PCs) analyses of temperature-sensitive chronologies from northern Patagonia (thick line) and coastal Alaska (thin line) during the past400years. The northern Patagonia record is the leading PC resulting from an analysis of three upper elevation chronologies (year t and t + 1), whereas the coastal Alaska record is the leading PC from seven coastal chronologies (year t and t + 1). The Patagonia and Alaska records are significantly correlated at the 99.99% confidence level.

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