Reconstructing the annual mass balance of the Echaurren Norte glacier (Central Andes, 33.5° S) using local and regional hydroclimatic data

Abstract

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).

The 2010–2015 megadrought in central Chile: impacts on regional hydroclimate and vegetation

“…Nevertheless, the negative conditions since the early 20th century appear to be the driest period on record, preceded by a century long wet period. This transition is consistent with the precipitation-driven glacier mass-balance dynamics of the region (Masiokas et al, 2006), which exhibit a sustained glacier shrinking during the 20th century following Masiokas et al, 2009Masiokas et al, , 2016. Since the beginning of the 21st century the reconstruction has contained a sustained dry period ending in the MD.…”

“…At the end of September, the MD-mean fraction covered by snow was 61 ± 7 %, much smaller than the past decade mean (73 ± 9 %). Year-to-year variations in the midspring snow coverage in the upper Maipo basin closely follow the winter rainfall accumulation in the Andean foothills (r = + 0.73; see also Masiokas et al, 2016), so the reduced snowpack extent during MD is largely explained by the lack of precipitation, although some marginal effects of warmer conditions (see Sect. 6c) cannot be ruled out.…”

“…Rainfall exhibits substantial interannual variability historically associated with El Niño-Southern Oscillation (ENSO, e.g., Aceituno 1988;Montecinos et al, 2000;Montecinos and Aceituno, 2003). Since the early 1980s a precipitation decline has been evident along the coast (Quintana and Aceituno, 2012) and the Andes cordillera (Masiokas et al, 2016), accentuated by an uninterrupted rainfall deficit from 2010 to the present. Boisier et al (2016) made use of historical global circulation model results to establish that SSTforced circulation changes account for only about half of the precipitation trend.…”

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

“…With a mean elevation of 3500 m north of 35 • S, the Andes act as a permanent barrier to the humid air masses from the mid-latitude South Pacific Ocean. At high elevations in the Andes, the climate shows a Mediterranean regime with a marked precipitation peak during the cold months (April to October) and little precipitation during the warm summer season (November to March [20]). The precipitation pattern drives the CAA hydrological cycle, exemplified in Figure 2 for the Mendoza River.…”

“…In this sense, the knowledge of processes causing hydrological drought and its spatial variability is essential for a sustainable management of water resources [19]. Basins in the CAA have a marked snowmelt-driven hydrological regime, with a runoff peak in the warm season and low flows during winter months [20]. Above normal streamflows occur during El Niño years; however, during La Niña events, the occurrence of low snowfall-i.e., potential hydrological drought conditions-is not straightforward [21].…”