Developing reliable tree-ring based, multi-century reconstructions of Andean snowpack and river discharges between 30° and 37°S

MASIOKAS, M.H.; VILLALBA, R.; LEQUESNE, C.; CHRISTIE, D.; BETMAN, E.; LUCKMAN, B.H.

Valdivia

Encuentro; Documenting, understanding and projecting changes in the hydrological cycle in the American Cordillera. IAI Collaborative Research Network 2047, Third Science Meeting; 2010

The meltwater from the snowpack accumulated each winter in the Andes between ca. 30° and 37°S is a crucial resource for the human populations in central Chile and central-western Argentina. Recent studies of the available snowpack and streamflow records have improved our knowledge about the inter-annual and inter-decadal hydrologic variability in this region and its relationships with large-scale atmospheric features such as ENSO and the PDO. In order to capture and analyze the full range of decade- to century-long fluctuations in this region’s water resources, we are testing a series of multiple regression models and preliminary reconstructions of snowpack and streamflows using the well-replicated, moisture-sensitive tree-ring width chronologies from the Chilean side of the central Andes. The best models were invariably found when the tree-ring chronologies located north of 35°S were included in the equations as these series showed positive strong, and time-stable correlations with the instrumental records. Interestingly however, for the longest streamflow records (Río San Juan, Mendoza, Atuel in Argentina, and Aconcagua in Chile), the models performed relatively poorly (50% variance explained) when the calibration period was truncated to the last 50-60 years of records. These and other options tested (e.g. use of the raw or log transformed data, residual or standard chronologies) and their corresponding results will be discussed in the presentation together with possible innovative ways of validating the resulting reconstructions using independent information.