The tree-ring d18O network from southernmost Patagonia: A recorder of large-scale climate modes and their spatial-temporal variability

Abstract

The Southern Patagonian Andes are located within the core zone of the Southern Hemispheric Westerlies (SHW). The North-South orientated Andean Cordillera is perpendicular to the main flow of moist airmasses triggered by different large-scale atmospheric circulation patterns like the Antarctic Oscillation (AAO). In recent decades, especially southernmost South America (50–56◦ S) has experienced a profound climate change resulting in rising temperatures, an increase in the variation of precipitation, and increased severe droughts (e.g. the recent Chilean Megadrought) that can be related to variations in atmospheric circulation over varied timescales. Up to now, a quantification of these changes in a context pre-1950´s stays difficult, due to scarce and fragmentated available climate station data. In combination with a complex regional topography and resulting scetchy ecoclimatic zones the impacts of the current environmental change are yet not well assessed. Within this study we present the up to date most dense network of d18Otree-ring series for southern South America based on two Nothofagus tree species. We can demonstrate, that the inherent climate signals in our proxy series is a highly suitable annual resolved archive to capture variations in the AAO and therefore can capture the long-term and short-term geographical migration (North-South) of the SHW. In addition, combined analyses of large-scale synoptic weather patterns (mean weather types; Grosswetterlagen, GWL) and backward trajectory modeling clearly reveal a highly significant influence of the moisture origin on the variations of the d18Otree-ring series.