Andean snowpack and streamflow variations in recent and historic times in central Chile and central-western Argentina Mariano Masiokas Ricardo Villalba Brian Luckman Elma Montaña Duncan Christie Carlos Le Quesne Ernesto Betman Steven Mauget

Santiago, Chile Mendoza, Argentina The winter snowpack in the Andes between 30° and 37°S is arguably the single most important natural resource in semi-arid central Chile and central-western Argentina Andean snowpack is the primary water supply and main source of surface runoff Over 10 million people depend on the mountain meltwater for domestic consumption, irrigation, industries, hydroelectric generation and aquifer rechargeIntroduction

We developed regional snowpack and streamflow records using the longest and most complete series

Comparison between regional snowpack and streamflow series Correlation of snowpack vs. discharges Jul-Jun = 0.933; discharges Nov-Feb = 0.949

Wettest % % % % % Driest % % % % % List of extreme years (5 driest and wettest years) in the central Andes of Chile and Argentina, Ranking (all expressed as percentages of the mean)

Records from both sides of the Andes show striking similarities El Niño events are generally associated with wet years; La Niña years usually result in dry years

Correlations between regional snowpack record and mid-winter (Jun-Sep) Sea Surface Temperatures and Sea Level Pressures Field correlation maps corroborate the strong ENSO-related influence on the inter-annual hydrologic variability of this region SSTSLP

Average 500-hPa geopotential height anomalies for the 10 snowiest and driest years ( ) 10 snowiest years 10 driest years Snowpack variations are also influenced by conditions in the Amundsen-Bellingshausen Seas

Analyses of the main temporal features in the regional Jul- Jun streamflow record showed: 1.Non-significant linear trend, strong year-to-year fluctuations 2.Two significant regime shifts in 1945 (-31%) and in 1977 (+28%)

Relative magnitude and statistical significance of 5-20 yr moving windows in the regional mean annual streamflow record 5-year moving windows

Relative magnitude and statistical significance of 5-20 yr moving windows in the regional mean annual streamflow record 10-year moving windows

Relative magnitude and statistical significance of 5-20 yr moving windows in the regional mean annual streamflow record 15-year moving windows

Relative magnitude and statistical significance of 5-20 yr moving windows in the regional mean annual streamflow record 20-year moving windows

Driest and wettest periods on record 1.Driest period on record: (p<0.01); 2 nd driest: Wettest period on record: (p<0.05); 2 nd wettest:

Statistically significant regime shifts in 1945 and 1977 coincide almost exactly with well-known shifts in the Pacific Decadal Oscillation (PDO) PDO influencing the low frequency modes of hydroclimatic variability in the study area? Extended wet periods coincide with “warm” phases of the PDO, dry period coincide with “cool” phase of PDO

It is possible to reconstruct winter snow accumulation using complementary information from different “proxies” Central Chile rainfall and precipitation- sensitive tree-ring width series show strong similarities with the regional snowpack series These proxy series allow inferring snowpack changes over the past two to eight centuries

Reconstructing Andean snowpack offers the opportunity of assessing the patterns of recent decades in a long term context since AD 1866 since AD 1150

Integration of Chilean and Argentinean hydrological data provided reliable, regionally representative records Regional snowpack and annual streamflow records show striking similarities that highlight the strong common hydrologic signal in this region and the good quality of the original data Two significant regime shifts in 1945 (-) and 1977 (+) were identified that mark the transition between three well defined low frequency modes of variability. In addition to ENSO, PDO may be influencing decadal hydrological patterns in this region Conclusions I

- Good quality, multi-centennial, annually-resolved snowpack reconstructions are possible at these latitudes - These quantitative reconstructions provide important information on past hydroclimatic variations in the southern Andes - Paleoclimate research - Water management - Climate modeling - Extended hydrologic information also help to understand current conditions in a long term context and provide a range of possible scenarios for the future - This type of hydro-climatic information may help understand the functioning of the coupled natural and social systems modulating the the majority of socio-economic activities of the oases in this region Conclusions II

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