Intra- to Multidecadal Variations of Snowpack and Streamflow Records in the Andes of Chile and Argentina between 30° and 37°S

Abstract

In a recent study the authors developed the first regionally averaged, transnational records of snowpack and streamflow for the Andes between 30° and 37°S using Chilean and Argentinean data. That study was mainly intended to evaluate the relationships between the interannual variations in the regional snowpack record and large-scale atmospheric variables and indices. Here the focus is on the main intra- to multidecadal variations in updated records of winter snowpack and mean annual river flows. River discharges show similar temporal variations on both sides of the Andes with extreme dry conditions concentrated between the mid-1940s and 1976/77 and extreme wet conditions peaking between the late 1970s and the 1980s. A regional streamflow composite (1906–2007) has a nonsignificant negative trend but significant regime shifts in 1945, when mean levels dropped 31%, and in 1977 when they increased 28%. These events coincide almost exactly with well-known shifts in the Pacific decadal oscillation (PDO). The analyses are preliminary but suggest a PDO influence on the low-frequency modes of hydroclimatic variability in the study area. Analyses of the magnitude of 5–20-yr moving windows in the regional streamflow composite indicate that the most significant concentration of high (low) discharges occurred between 1977 and 1987 (1954 and 1971). Snowpack series show a more heterogeneous pattern of variations on a local basis but when aggregated into a regional series (1951–2008) they share remarkable similarities with river flows. However, the snowpack composite has a stronger year-to-year variability, a slight positive trend, and no significant regime shifts.

Spatio-Temporal Patterns of the 2010–2015 Extreme Hydrological Drought across the Central Andes, Argentina

“…A strong non-linearity in the behavior of long-term trends was observed considering the seasonal number of days with low flows [25], linked to the decadal behavior of the PDO. The cold (warm) phase of the PDO is linked to below (above)-average winter snowpacks and annual discharges [25,57]. Nevertheless, Boisier et al [5] have shown that the PDO accounts for half of the recent precipitation trends recorded in the Central Andes.…”

Spatiotemporal Variations in Hydroclimate across the Mediterranean Andes (30°–37°S) since the Early Twentieth Century

“…Despite these differences in precipitation regime on both sides of the Andes, streamflow, which originates from snow and glacier melt in the Andes Mountains, shows a common seasonal regime for both slopes of the Andes (Masiokas et al 2013), common for energydriven hydrological systems. As a result, Argentinean and Chilean river flows in the MA show a strong mean intercorrelation over the snowmelt season (mean r 5 0.83; P , 0.001; 1954-2007 period).…”

“…The Mediterranean Andes region (MA; 308-378S) is located in the transition between two major macroclimate regions in South America, namely, the subtropical desert Andes to the north and the wet temperate Andes to the south (Lliboutry 1998). Several studies in the region have identified recent environmental changes characterized by 1) an increase of mean air temperature (10.258C decade 21 ) during the last three decades (1979Falvey and Garreaud 2009); 2) a reduction of the area covered by glaciers (Bown et al 2008;Masiokas et al 2009); 3) an increase of the 08C isotherm (Carrasco et al 2008); and 4) a negative, although not significant, precipitation trend since the beginning of the twentieth century (Vuille and Milana 2007;Le Quesne et al 2009;Quintana and Aceituno 2012). The rivers in the MA provide freshwater to around 10 million people on both sides of the Andes Mountains in Chile and Argentina (Fig.…”

“…1). These rivers are fed by precipitation during winter and by the melting of the snowpack in the high mountains during spring and summer (Masiokas et al 2006). Large-scale climate forcings, such as El Niño-Southern Oscillation (ENSO), have strong influences over the MA climate.…”

“…Large-scale climate forcings, such as El Niño-Southern Oscillation (ENSO), have strong influences over the MA climate. El Niño (La Niña) conditions are usually associated with years of above (below) average winter precipitation (Rutllant and Fuenzalida 1991;Montecinos and Aceituno 2003), abundant (reduced) snowpack accumulation (Masiokas et al 2006), and a concurrent increase (decrease) in river discharge (Aceituno and Garreaud 1995;Cortés et al 2011). On the other hand, the positive (negative) phase of the Pacific decadal oscillation (PDO) has been associated with abundant (reduced) precipitation ) as well as above (below) average snowpack accumulation and streamflows in the MA (Masiokas et al 2010).…”