Dendroclimatology from regional to continental scales: Understanding regional processes to reconstruct large-scale climatic variations across the Western Americas

VILLALBA, LUCKMAN, BONINSEGNA, D'ARRIGO, LARA, VILLANUEVA-DÍAZ, MASIOKAS, ARGOLLO, SOLIZ, LE-QUESNE, STHALE, ROIG, ETC

Dendroclimatology: Progress and Prospects

Springer

Lugar: Heidelberg; Año: 2011; p. 175 - 227

Common patterns of climatic variability across the Western Americasare modulated by tropical and extra-tropical oscillatory modes operating at differenttemporal scales. Interannual climatic variations in the tropics and subtropics of theWestern Americas are largely regulated by El Niño-Southern Oscillation (ENSO),whereas decadal-scale variations are induced by long-term Pacific modes of climatevariability such as the Pacific Decadal Oscillation (PDO). At higher latitudes,climate variations are dominated by oscillations in the Annular Modes (the Arcticand Antarctic Oscillations) which show both interannual and longer-scale temporaloscillations. Here we use a recently-developed network of tree-ring chronologiesto document past climatic variations along the length of the Western Cordilleras.The local and regional characterization of the relationships between climate andtree-growth provide the basis to compare climatic variations in temperature- andprecipitation-sensitive records in the Western Americas over the past 3–4 centuries.Upper-elevation records from tree-ring sites in the Gulf of Alaska and Patagoniareveal the occurrence of concurrent decade-scale oscillations in temperature duringthe last 400 years modulated by PDO. The most recent fluctuation from thecold- to the warm-phase of the PDO in the mid 1970s induced marked changes in tree growth in most extratropical temperature-sensitive chronologies in the WesternCordilleras of both Hemispheres. Common patterns of interannual variations intree-ring chronologies from the relatively-dry subtropics in western North andSouth America are largely modulated by ENSO. We used an independent reconstructionof Niño-3 sea surface temperature (SST) to document relationships totree growth in the southwestern US, the Bolivian Altiplano and Central Chile andalso to show strong correlations between these regions. These results further documentthe strong influence of SSTs in the tropical Pacific as a common forcingof precipitation variations in the subtropical Western America during the past 3–4centuries. Common patterns of interdecadal or longer-scale variability in tree-ringchronologies from the subarctic and subantarctic regions also suggest common forcingsfor the annular modes of high-latitude climate variability. A clear separationof the relative influence of tropical versus high-latitude modes of variability iscurrently difficult to establish: discriminating between tropical and extra-tropicalinfluences on tree growth still remains elusive, particularly in subtropical and temperateregions along our transect. We still need independent reconstructions oftropical and polar modes of climate variability to gain insight into past forcing interactionsand the combined effect on climates of the Western Americas. Finally, wealso include a series of brief examples (as ‘boxes’) illustrating some of the majorregional developments in dendrochronology over this global transect in the last10 years.