Indicators of present global warming through changes in active layer-thickness, estimation of thermal diffusivity and geomorphological observations in the Morenas Coloradas rockglacier, Central Andes of Mendoza, Argentina (original) (raw)
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Monitoring of Mountain Permafrost in the Central Andes, Cordon del Plata, Mendoza, Argentina
Permafrost and Periglacial Processes, 1997
ABSTRACT Sixty per cent of the Rio Blanco basin (54 km2), located between 32°54′ and 33°01′S and between 69°27′ and 69°15′W, in the Cordón del Plata, Frontal Cordillera, can be considered to be periglacial. The most important forms in the area are rock glaciers, two of which, Morenas Coloradas and El Salto, are active down to 3400 and 3600 m ASL respectively. The rock glaciers are not in equilibrium with the present climate since the mean annual air temperature is 1.6°C at 3560 m ASL and the 0°C air isotherm is calculated to be at 3860 m ASL. A third landform is the cryoplanation surface Lagunita del Plata which, at an elevation of approximately 4000 m ASL, has a mean annual temperature of −2°C and contains bodies of insular permafrost. © 1997 John Wiley & Sons, Ltd.Soixante pour cent du bassin du Rio Blanco (54 km2), situé entre 32°54′ et 33°01′S et entre 69°27′ et 69°15′ ouest, dans le “Cordon del Plata, Frontal Cordillera” peuvent être considérés comme périglaciaires. Les formes les plus importantes de la région sont des glaciers rocheux dont deux d'entre eux, “Morenas Coloradas” et “El Salto”, sont actifs respectivement jusqu'à 3400 m et 3600 m d'altitude. Les glaciers rocheux ne sont pas en équilibre avec le climat actuel bien que la température moyenne actuelle de l'air est de 1.6 °C à 3560 m et que l'isotherme de l'air est, par calcul, estimée se trouver à 3860 m d'altitude. Une troisième forme est la surface de cryoplanation “Lagunita del Plata” qui, à une altitude d'approximativement 4000 m au dessus du niveau de la mer, a une température moyenne annuelle de −2°C et contient de îlots de pergélisol. © 1997 John Wiley & Sons, Ltd.
Permafrost activity and atmospheric warming in the Argentinian Andes
Geomorphology, 2018
Rock glaciers are permafrost or glacial landforms of debris and ice that deform under the influence of gravity. Recent estimates hold that, in the semiarid Chilean Andes for example, active rock glaciers store more water than glaciers. However, little is known about how many rock glaciers might decay because of global warming and how much this decay might contribute to water and sediment release. We investigated an inventory of >6500 rock glaciers in the Argentinian Andes, spanning the climatic gradient from the Desert Andes to cold-temperate Tierra del Fuego. We used active rock glaciers as a diagnostic of permafrost, assuming that the toes mark the 0°C isotherm in climate scenarios for the twenty-first century and their impact on freezing conditions near the rock glacier toes. We find that, under future worst case warming, up to 95% of rock glaciers in the southern Desert Andes and in the Central Andes will rest in areas above 0°C and that this freezing level might move up more than twice as much (~500 m) as during the entire Holocene (~200 m). Many active rock glaciers are already well below the current freezing level and exemplify how local controls may confound regional prognoses. A Bayesian Multifactor Analysis of Variance further shows that only in the Central Andes are the toes of active rock glaciers credibly higher than those of inactive ones. Elsewhere in the Andes, active and inactive rock glaciers occupy indistinguishable elevation bands, regardless of aspect, the formation mechanism, or shape of rock glaciers. The state of rock glacier activity predicts differences in elevations of toes to 140 m at best so that regional inference of the distribution of discontinuous permafrost from rock-glacier toes cannot be more accurate than this in the Argentinian Andes. We conclude that the Central Andes-where rock glaciers are largest, cover the most area, and have a greater density than glaciers-is likely to experience the most widespread disturbance to the thermal regime of the twenty-first century.
Survey of cryogenic processes, periglacial forms and permafrost conditions in South America
Revista do Instituto Geológico, 2000
Este inventário fornece informações sobre o estado da arte e os avanços recentes da Geocriologia nos países da América do Sul onde ocorre permafrost ou congelamento sazonal dos solos e onde este campo de pesquisa tem interesse científico. O objetivo é aumentar o conhecimento das atuais áreas geocriogênicas sob impacto de influências antrópicas e/ou de modificações climáticas. Uma breve análise climática ajuda a compreender as principais regiões criogênicas sul-americanas, ainda pouco conhecidas e sem a correspondente cartografação geomorfológica. O levantamento também salienta o fato de haver poucos dados disponíveis sobre a degradação do permafrost andino de altitude. Esta degradação, causada pelos processos de aquecimento global, deveria ser monitorada, entre outras, por razões hidrológicas. Os principais processos criogênicos-como criometeorização, nivação, solifluxão, crioturbação e seleção-são descritos em diferentes litologias, lugares, etc .. São fornecidos alguns dados quantitativos sobre movimentos de solifluxão e aplicação de métodos sedimentológicos na detecção de fenômenos criogênicos. São resumidos os últimos dados sobre permafrost andino, obtidos com o auxílio de métodos geofísicos e/ou sondagens acompanhadas de medidas da temperatura do solo. As forrnas criogênicas mais comuns nos Andes são apresentadas: microforrnas, patterned ground, felsenmeer, estruturas de crioturbação, thufurs em moors e lobos de solifluxão. Mesoforrnas características dos rock glaciers dos Andes Centrais e elementos importantes de ambiente periglacial como vertentes criogênicas de sedimentação, superfícies de crioplanação ou vales assimétricos são também descritos. Palavras-chave: Geocriologia-permafrost-periglacial-Andes-regiões criogênicas-Geomorfologia
Permafrost occurrence in southernmost South America (Sierras de Alvear, Tierra del Fuego, Argentina)
Several lines of evidence indicate that permafrost is present at elevations above ca. 775 m a.s.l. in the Mount Alvear region of the Sierras de Alvear, Fuegian Andes, Argentina. Ground temperatures recorded to depths of 1.3 m in sorted circles remain near 0°C in late summer and suggest perennial frozen ground at a depth of approximately 1.5 to 2 m. Three active rock glaciers occur in the upper Alvear Valley. On the flat surface to the east of the Alvear Glacier, sorted circles are located in the centres of poorly-defined polygons. The latter are interpreted to reflect either joint widening in underlying bedrock or thermal-contraction cracking in bedrock. Collectively, this evidence suggests the presence of permafrost on the higher summits of the Fuegian Andes.
Status and evolution of the cryosphere in the Andes of Santiago (Chile, 33.5°S.)
Geomorphology
In the context of a general retreat of glaciers in the dry Andes, this study focuses on the state and recent evolution of debris-covered glaciers and permafrost-related landforms, especially rock glaciers, in the semiarid to semihumid Laguna Negra catchment, a part of the Andes of central Chile at 33.5°S, that is a key contributor of drinking water for the city of Santiago. We conducted catchment-scale geomorphological mapping, diachronic analysis of 1955 and 1996 orthophotographs and digital elevation models (DEMs), and the analysis of ground temperatures and their sensitivity to climate variation. Rock glaciers dominate spatially and in terms of water storage over glaciers (area ratio: 1.7:1; ratio of water equivalents: 1.5:1). An intense downwasting has affected both debris-covered and exposed glacier components in the Punta Negra subcatchment, a process that is associated with the growth of numerous thermokarst depressions. The altitudinal transect of ground temperature suggest that permafrost is widespread above ∼4000 m asl, although it can also occur at lower elevations on sheltered footslopes and within rock glaciers. The sensitivity analysis indicates that the near-surface ground thermal regime at high altitudes is strongly influenced by the snow cover disappearance date, which may therefore constitute an important control on the effect of climatic warming.
GeoResJ, 2017
Recent studies have revealed that in high-altitude mountain environments the global warming trend over the last few decades tends to be strongly amplified. However, few attempts have been made to monitor the possible effects of such climate changes on highaltitude rock glaciers. In this paper, we provide a geomorphic analysis of the Varas rock glacier, and present the first observations of rock glacier temperature (air and ground) and surface velocities in the Andes of northwestern Argentina. A network of 30 boulders was monitored every year between 2012 and 2016 using a differential Global Positioning System. Over the observational period, the Varas active rock glacier registered velocities between 125 and 5 cm/yr, except for four boulders which did not shift. Over the five years of monitoring, the mean annual air and ground (at 5 and 50 cm depth) temperature remained above 0 ºC. A long-term instrumental weather dataset (106 years), located ~130 km from the Varas rock glacier, at La Quiaca station, reveals a warming trend of 0.8 ºC during the last century, with a steep increase during the last two and half decades. The warming trend recorded in the region may have produced or facilitated the inactivity of the more-exposed sectors of the Varas active rock glacier. However, there also may be a delay in the, relatively slow, and full response of rock glaciers to the last few decades of warming. Finally, the observations allow us to propose a formation sequence in the Varas rock glacier valley, since postglacial time.
Most of the population of Peru is concentrated in cities located in the narrow area between the Pacific Ocean and the Central Andes. This is one of the most arid regions of the Earth, where the total annual rainfall barely reaches few tens of mm. For this reason the water resources of the population and the economic activities rely heavily on the glaciers that remain in the mountains. These ice masses are part of the cryosphere, along with snow, rock glaciers and layers of frozen ground (permafrost), which are also gaining importance as water reserves, due to a strong tendency observed during the last decades, the reduction on surface and volume of glaciers. The deglaciation process also involves an increase of geological hazards associated with the cryosphere, such as avalanches, landslides and other types of mass movements. The risk is even greater in the slopes of the mountain range as a result of its steep slopes. In this context, the National Water Authority of Peru (Autoridad ...
2010
At high elevations of the Argentinean and Chilean Andes permafrost conditions can frequently be found in various forms. Its characteristics are of great importance to any development in these areas, particularly the role of the ground ice within the hydrological cycle. Preliminary investigations were initiated by Xstrata Copper San Juan, including surface geophysics, shallow boreholes, ground temperature monitoring, and test pit excavations. With focus on two active rock glacier, multi-faceted investigations confirmed the permafrost setting and evidenced presence of subsurface ice. These initial results help studying the hydrological setting of the El Pachón valley of the San Juan Province, Argentina. RÉSUMÉ À haute altitudes de l’Andes de l'Argentine et du Chili pergélisol peuvent être trouvées fréquemment dans diverses formes de pierres sèches aux sols riches en glace. Les caractéristiques et les conditions son d’une grande importance pour les développements dans ces domaines,...
The Cryosphere Discussions, 2016
This paper presents a detailed rock glacier inventory used in determining how the various natural parameters affect a mountain periglacial environment. This study was undertaken in a northernmost sector of the central Argentine Andes, in an area stretching between 31°02' and 31°22' S latitude. This is a high and arid subtropical region where permafrost and cryogenic processes are predominant, featuring as well as a large number of rock glaciers and associated periglacial landforms. Rock glaciers inventory was based on geomorphological characterization with optical remote sensing data and field description information. The study region covers 630 km<sup>2</sup>, with 3,25 % of this area showing 402 rock glaciers and protalus rampart features. In total, 172 rock glaciers have been identified, 48 of which are considered active. In such a sector, the protalus rampart range shows the largest landform occurrences, though fossil and inactive rock gl...
Climate changes and recent glacier behaviour in the Chilean Lake District
Global and Planetary Change, 2007
Atmospheric temperatures measured at the Chilean Lake District (38°-42°S) showed contrasting trends during the second half of the 20th century. The surface cooling detected at several meteorological stations ranged from −0.014 to −0.021°C a − 1 , whilst upper troposphere (850-300 gpm) records at radiosonde of Puerto Montt (41°26′S/73°07′W) revealed warming between 0.019 and 0.031°C a − 1 . Regional rainfall data collected from 1961 to 2000 showed the overall decrease with a maximum rate of −15 mm a − 2 at Valdivia st. (39°38′S/73°05′W). These ongoing climatic changes, especially the precipitation reduction, seem to be related to El Niño-Southern Oscillation (ENSO) phenomena which has been more frequent after 1976. Glaciers within the Chilean Lake District have significantly retreated during recent decades, in an apparent out-of-phase response to the regional surface cooling. Moreover, very little is known about upper troposphere changes and how they can enhance the glacier responses. In order to analyse their behaviour in the context of the observed climate changes, Casa Pangue glacier (41°08′S/71°52′W) has been selected and studied by comparing Digital Elevation Models (DEMs) computed at three different dates throughout the last four decades. This approach allowed the determination of ice elevation changes between 1961 and 1998, yielding a mean thinning rate of −2.3 ± 0.6 m a − 1 . Strikingly, when ice thinning is computed for the period between 1981 and 1998, the resulting rate is 50% higher (−3.6 ± 0.6 m a − 1 ). This enhanced trend and the related area loss and frontal retreat suggests that Casa Pangue might currently be suffering negative mass balances in response to the upper troposphere warming and decreased precipitation of the last 25-30 yr, as well as debris cover would not prevent the glacier from a fast reaction to climate forcing. Most of recent glaciological studies regarding Andean glaciers have concentrated on low altitude changes, namely frontal variations, however, in order to better understand the regional glacier changes, new data are necessary, especially from the accumulation areas.