Patterns of glacier ablation acrossNorth‐CentralChile: Identifying the limits of empirical melt models under sublimation‐favorable conditions

Abstract

We investigate the energy balance and ablation regimes of glaciers in high‐elevation, dry environments using glaciometeorological data collected on six glaciers in the semiarid Andes of North‐Central Chile (29–34°S, 3127–5324 m). We use a point‐scale physically based energy balance (EB) model and an enhanced Temperature‐Index (ETI) model that calculates melt rates only as a function of air temperature and net shortwave radiation. At all sites, the largest energy inputs are net shortwave and incoming longwave radiation, which are controlled by surface albedo and elevation, respectively. Turbulent fluxes cancel each other out at the lower sites, but as elevation increases, cold, dry and wind‐exposed conditions increase the magnitude of negative latent heat fluxes, associated with large surface sublimation rates. In midsummer (January), ablation rates vary from 67.9 mm w.e. d−1 at the lowest site (∼100% corresponding to melt), to 2.3 mm w.e. d−1 at the highest site (>85% corresponding to surface sublimation). At low‐elevation, low‐albedo, melt‐dominated sites, the ETI model correctly reproduces melt using a large range of possible parameters, but both the performance and parameter transferability decrease with elevation for two main reasons: (i) the air temperature threshold approach for melt onset does not capture the diurnal variability of melt in cold and strong irradiated environments and (ii) energy losses decrease the correlation between melt and net shortwave radiation. We summarize our results by means of an elevation profile of ablation components that can be used as reference in future studies of glacier ablation in the semiarid Andes.

Understanding snow hydrological processes through the lens of stable water isotopes

“…A special case is that of dry mountains with sporadic snowfall that is retained due to generally cold temperatures, such as in the very high elevation but largely arid Andes (MacDonell, Kinnard, Molg, Nicholson, & Abermann, 2013). Sublimation plays a key role in snow ablation, occurring yearround under the influence of solar radiation and wind (Ayala, Pellicciotti, MacDonell, McPhee, & Burlando, 2017;Gascoin, Lhermitte, Kinnard, Bortels, & Liston, 2013). In general, sublimation is a potentially important driver of snow ablation in drier climates (see, for example, the review on Mediterranean snow hydrology by Fayad et al (2017b)), and in cold and windy climates (due to the stronger sublimation of blowing snow (Law & Vandijk, 1994)), for example, in many high-elevation and high-latitude regions such as the Canadian Rocky Mountains (MacDonald, Pomeroy, & Pietroniro, 2010).…”

Glacier runoff variations since 1955 in the Maipo River Basin, semiarid Andes of central Chile

“…We choose a set of model parameters typically used in the literature for this region (Ragettli and Pellicciotti, 2012;Ayala et al, 2016;Burger et al, 2018a) for all individual glacier models and keep parameter calibration at a minimum level. For each glacier, we vary only the ETI model parameters within ranges suggested in the literature (Finger et al, 2011;Ragettli and Pellicciotti, 2012;Ayala et al, 2017a) to fit the glacier-wide mass balance as derived from the geodetic mass balances. A summary of literature-derived and calibrated parameters for the individual models is shown in Table 1.…”

“…In relation to TOPKAPI-ETH, it has been shown that the parameterizations of snow accumulation and ablation included in 530 TOPKAPI-ETH work well for wind-sheltered locations (Ayala et al, 2017a). However, the representation of processes driving the mass balance at some specific sites requires more fundamental work, and additional parameterizations or more physicallybased representations are required.…”

“…However, the representation of processes driving the mass balance at some specific sites requires more fundamental work, and additional parameterizations or more physicallybased representations are required. Such sites correspond mainly to sublimation-dominated sites above 5500 m a.s.l., where the temperature-index modelling is inaccurate (Ayala et al, 2017a(Ayala et al, , 2017b, debris-covered areas with complex distributions of debris thickness (Burger et al, 2018a), or steep glacierized slopes such as the volcanoes in the Maipo River Basin. 535…”

Snow Depth Patterns in a High Mountain Andean Catchment from Satellite Optical Tristereoscopic Remote Sensing

“…The spatial heterogeneity of the snow cover can be attributed to local precipitation events that are strongly affected by the interaction of the terrain elevation with the local climate (Mott et al, ). The preferential distribution of initial snow cover on favorable slopes and aspects may be subsequently redistributed by wind (Essery et al, ; Gascoin et al, ; Lehning et al, ; Schirmer & Lehning, ; Trujillo et al, ) or avalanching (Bernhardt & Schulz, ; Ragettli et al, ), thus adjusting the shape of the seasonal hydrograph (Freudiger et al, ), the potential melt‐sublimation ratio (Ayala et al, ), and the mass balance of glacierized basins (Gascoin et al, ; McGrath et al, ). Furthermore, the resulting spatial snow distribution can be governed by the radiation forcing of the surface slope relative to the local solar zenith and azimuth angle of the sun (Ayala et al, ), promoting higher quantities of snow on north‐facing slopes (in the Northern Hemisphere), and delaying melt onset.…”