干旱区生态环境知识资源中心

This paper presents an inventory and a morphologic characterization of the rock glaciers in the arid region of the Argentinean Cordillera Oriental (22-25 degrees S), and discusses the climatic significance and the factors controlling their distribution. We also present a detailed characterization of the Varas rock glacier, which is located in the southern part of the Zenta range where dynamic and climatic monitoring has been initiated. A total of 635 rock glaciers were identified, including 174 (25%) classified as active, 301 (47.5%) as inactive and 160 (25%) as fossil or relict. In general, the rock glaciers are small (<0.1 km(2)), with a mean area of 0.076 km(2). Rock glaciers distribution is associated with inherited Late Pleistocene glacial topography, which was also regulated by the regional climatic circulation system. The elevation of the lower limit of active rock glaciers is situated 416 m below the 0 degrees C isotherm, presenting positive mean annual temperatures, as recognized in other regions of the Central Andes. Climatic changes occurred after the Late Glacial period may have lead to the degradation and inactivation of rock glaciers. The difference between the lower altitude of active (4500 m) and relict (3800 m) rock glaciers was used to estimate a temperature rise of 4.9 degrees C in this region between deglatiation (after the Late Glacial period) and the twentieth century (prior 1990). Although the area covered by glaciers in the Argentinean Cordillera Oriental is small (<0.8 km(2)), the identified rock glaciers represent an important water source in this arid region.