The snowpack in the central Andes (30°-37°S) is the primary source for streamflow in central Chile and central-western Argentina, but few published studies are available on snowpack variability in the region. This paper develops the first regional snowpack series from Chilean and Argentinean snow course records. This series shows a strong regional signal, marked interannual variability, and a positive, though nonsignificant, linear trend. Correlations with local precipitation and temperature records reveal a marked association with conditions in central Chile. High snow accumulation is generally concurrent with El Niño events in the tropical Pacific, but only 5 of the 10 driest years coincided with La Niña events. Evaluation of 500-hPa geopotential height anomaly maps during extreme snow years highlights the crucial significance of tropospheric conditions in the subtropical and southeast Pacific in modulating snowfall. Correlations with gridded SST and SLP data and multiple regressions with large-scale climatic indices corroborate a Pacific ENSO-related influence largely concentrated during the austral winter months. This hampers the predictability of snowpack before the onset of the cold season. Annual and warm-season river discharges on both sides of the cordillera are significantly correlated with the regional snowpack record and show positive linear trends over the 1951-2004 common period, probably related to a greater frequency of above-average snowpacks during recent decades. Future demand and competition for water resources in these highly populated regions will require detailed information about temporal and spatial variations in snow accumulation over the Andes. The results indicate that the relationships between snowpack and atmospheric circulation patterns prior to the winter season are complex, and more detailed analyses are necessary to improve prediction of winter snowfall totals.

Abstract. Despite the great number and variety of glaciers in southern South America, in situ glacier mass-balance records are extremely scarce and glacier-climate relationships are still poorly understood in this region. Here we use the longest ( > 35 years) and most complete in situ mass-balance record, available for the Echaurren Norte glacier (ECH) in the Andes at ∼ 33.5 • S, to develop a minimal glacier surface massbalance model that relies on nearby monthly precipitation and air temperature data as forcing. This basic model is able to explain 78 % of the variance in the annual glacier massbalance record over the 1978-2013 calibration period. An attribution assessment identified precipitation variability as the dominant forcing modulating annual mass balances at ECH, with temperature variations likely playing a secondary role. A regionally averaged series of mean annual streamflow records from both sides of the Andes between ∼ 30 and 37 • S is then used to estimate, through simple linear regression, this glacier's annual mass-balance variations since 1909. The reconstruction model captures 68 % of the observed glacier mass-balance variability and shows three periods of sustained positive mass balances embedded in an overall negative trend over the past 105 years. The three periods of sustained positive mass balances (centered in the 1920s-1930s, in the 1980s and in the first decade of the 21st century) coincide with several documented glacier advances in this region. Similar trends observed in other shorter glacier mass-balance series suggest that the Echaurren Norte glacier reconstruction is representative of larger-scale conditions and could be useful for more detailed glaciological, hydrological and climatological assessments in this portion of the Andes.Published by Copernicus Publications on behalf of the European Geosciences Union. Peña and Narbona, 1978). Note that the glacier has remained in roughly the same position but has thinned markedly over the last decades. Panel (d) shows seasonal variations in temperature and precipitation at the lower reaches of ECH (3700 m a.s.l.) extrapolated from the El Yeso meteorological station (see Sect. 2.2 for details). Note that the bulk of precipitation occurs during the coldest months of the year (December-March precipitation only accounts for ∼ 5 % of the mean annual totals).

An expanded network of moisture-sensitive tree-ring chronologies has been developed for central Chile from long-lived cypress trees in the Andean Cordillera. A regional ring width chronology of cypress sites has been used to develop well-calibrated and verified estimates of June-December precipitation totals for central Chile extending from A.D. 1200 to 2000. These reconstructions are confirmed in part by historical references to drought in the seventeenth and eighteenth centuries and by nineteenth-century observations on the position of the Río Cipreses glacier. Analyses of the return intervals between droughts in the instrumental and reconstructed precipitation series indicate that the probability of drought has increased dramatically during the late nineteenth and twentieth centuries, consistent with selected long instrumental precipitation records and with the general recession of glaciers in the Andean Cordillera. This increased drought risk has occurred along with the growing demand on surface water resources and may heighten socioeconomic sensitivity to climate variability in central Chile.

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