Computation of the space and time evolution of equilibrium-line altitudes on Andean glaciers (10°N–55°S)

Abstract

A previous study of Fox [Fox, A.N. 1993. Snowline altitude and climate at present and during the Last Pleistocene Glacial Maximum in the Central Andes (5°-28°S). Ph.D. Thesis. Cornell University.] showed that for a fixed 0°C isotherm altitude, the equilibrium-line altitude (ELA) of the Peruvian and Bolivian glaciers from 5 to 20°S can be expressed based on a log-normal expression of local mid-annual rainfall amount (P). In order to extrapolate the function to the whole Andes (10°N to 55°S) a local 0°C isotherm altitude is introduced. Two applications of this generalised function are presented. One concerns the space evolution of mean inter-annual ELA for three decades ) over the whole South American continent. A high-resolution data set (grid data: 10′ for latitude/longitude) of mean monthly air surface temperature and precipitation is used. Mean annual values over the 1961-1990 period were calculated. On each grid element, the mean annual 0°C isotherm altitude is determined from an altitudinal temperature gradient and mean annual temperature (T ) at ground level. The 0°C isotherm altitude is then associated with the annual precipitation amount to compute the ELA. Using computed ELA and the digital terrain elevation model GTOPO30, we determine the extent of the glacierised area in Andean regions under modern climatic conditions. The other application concerns the ELA time evolution on Zongo Glacier (Bolivia), where inter-annual ELA variations are computed from 1995 to 1999. For both applications, the computed values of ELA are in good agreement with those derived from glacier mass balance measurements.

Rapid decline of snow and ice in the tropical Andes – Impacts, uncertainties and challenges ahead

“…In addition the coupling between largescale climatic information, derived from historical simulations or future projections of climate change, and glaciologic and hydrologic models requires downscaling of the climate information to the catchment scale to bridge this scale mismatch. Some studies have circumvented this problem by general approximations of temperature focusing on the close coupling between the ELA of tropical glaciers and the 0°C isotherm (the freezing level) (Condom et al, 2007;Rabatel et al, 2012;Sagredo et al, 2014), while others have exploited the relationship between freezing level height (FLH) and glacier extent . As shown in Fig.…”

Fluctuations of Glaciar Esperanza Norte in the north Patagonian Andes of Argentina during the past 400 yr

“…Most of these large remote glaciers are valley glaciers with compound basins that terminate at elevations as low as 1000 m. Rivera et al (2012) have found glaciers in this region that reach minimum elevations as low as 550 m a.s.l. Although no local meteorological information is available for most of these glaciers, there have been a few attempts (Condom et al, 2007;Carrasco et al, 2005 and to constrain the climatic Equilibrium Line Altitude (ELA) at a regional scale based on meteorological data from low altitude stations and scarce mass balance data (Rivera et al, 2006). These studies indicate that the climatic ELA in the region is around 1400 and 2000 m, suggesting that the abundant precipitation of the area would result in an ELA below the 0 • C isotherm.…”

Glacier Ablation and Water Resources in Tropical Andes: The Condoriri Glacier

“…The mean annual temperature at the Condoriri s tation located at 4490 meters above sea level (masl) is 3.3 °C. According to other studies, the temperature decreases with elevation at a r ate o f 0.7 °C ev ery 100 v ertical m eters 7) . T he relative h umidity cl early r eflects the seasonality.…”