Intensificación de la circulación atmosférica meridional en la región subtropical de América del sur inferida a partir de registros dendroclimatológicos

Résumé 0

"The main goal of this study is to show the use of tree-ring records to properly characterize the climatic changes which have affected the South American subtropics during the past two centuries. Tree-ring width chronologies from nogal criollo (Juglans australis) and cedro tucumano (Cedrela lilloi) have been used to estimate regional changes in temperature and precipitation since 1800. Similar to instrumental records, precipitation-sensitive chronologies indicate a steady increase of precipitation in the subtropics starting around 1950. This precipitation increase is unprecedented in the 200-year long tree-ring records. The mean sea-level pressure (MSLP) gradient between the tropics and subtropics, measured as the differences in MSLP between Cuiabá (15° S) and Reconquista (29° S), shows a increase since about 1950. This intensification of the pressure gradient, together with an increase in temperatures at the subtropics, appears to have induced a southward shift of the continental low pressure cell over South America. This southward displacement of the low pressure cell may have increased precipitation and reduced the extent of the dry season in the subtropics. Spatial correlation patterns between tree rings and sea-surface temperatures (SST) indicate that subtropical precipitation changes may also be related to a steady increase in SST in the South Atlantic during the past four decades. These results consistently show the large potential of tree-ring records to reconstruct climatic variations in the subtropics and to establish the relationships between regional climate and large-scale climatic forcing."