Dendroclimatic Research in the South American Sector of the Southern Ocean: Indicators of Atmosphere-Ocean Climate Variability
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A tree-ring chronology network recently developed from the subantarctic forests provides an opportunity to study long-term climatic variability at higher latitudes in the South American sector of the Southern Ocean. Based on the longest pressure records available in the South American-Antarctic Peninsula (SAAP) sector of the Southern Oceans, zonal and meridional indices have been developed for the region. Temperature records in southern South America and the Antarctic Peninsula are strongly affected by the strength of the meridional flow, whereas precipitation variations along the Pacific coast in southern South America are more related to changes in the zonal circulation at higher latitudes. We employed dendroclimatic techniques for reconstructing both the zonal (ZSAAP) and the meridional (MSAAP) circulation indices over the past four centuries. The ZSAAP reconstruction shows dominant modes of variation at around 4.4 and 5 years, which may be associated with the proposed Antarctic Circumpolar Wave in the Southern Oceans. Contrasting patterns in meridionality during the past two centuries are observed in the MSAAP reconstruction. Since the mid 1950s the northerly flow has steady increased, reaching unprecedented levels during the 1980s in the context of the past 400 years.