Drought variability across the Andes during the last millennium and its linkages to Pacific Ocean climate variability

CHRISTIE, DA; MORALES, MS; BARICHIVICH, J; COOK, E; LE QUESNE, C

Tilcara

Encuentro; Documenting, understanding and projecting changes in the hydrological cycle in the American Cordillera. IAI Collaborative Research Network 2047; 2011

Interamerican Institute for Global Change research IAI

Since the second half of the 20th century the Andes Cordillera has experienced a positive warming trend, an increase in elevation of the 0ºC isotherm, rapid melting of ice caps, and a sustained shrinkage of glaciers. These climate and environmental changes have occurred in conjunction with a growing demand for hydrological resources as a result of population increases and industrial development. Given the short span of instrumental hidroclimate records for this region, longer records are needed to understand the nature of climate variability and how the dominant interannual modes of climate variability have evolved under changes in long-term background conditions. We develop a field reconstruction of summer Palmer Drought Severity Index (PDSI) since AD 1200 from 10°S to 40°S latitude based on a multi species network of tree-ring chronologies from both flanks of the Andes. Our results show two dominant spatio-temporal modes, the first centered in the Altiplano region and the second in the Central Andes of Chile and Argentina (CCha). Both modes show an intermittent anti-phase relationship among themselves at high spectral frequencies and an increase in interannual variability within the ENSO band since the late XIX century. Sea surface temperatures from the central Pacific Ocean results negatively (positive) correlated with Altiplano (CChA) summer PDSI.