ABSTRACT. Despite renewed efforts to better understand glacier change and recognize glacier change trends in the Andes, relatively large areas in the Andes of Argentina and Chile are still not investigated. In this study, we report on glacier elevation and mass changes in the outer region of the Northern and Southern Patagonian Icefields in the Southern Patagonian Andes. A newly-compiled Landsat ETM+ derived glacier inventory (consisting of 2253 glaciers and ∼1314 ± 66 km 2 of ice area) and differencing of the SRTM and SPOT5 DEMs were used to derive glacier-specific elevation changes over the 2000-12 period. The investigated glaciers showed a volume change of −0.71 ± 0.55 km 3 a −1 , yielding a surface lowering of 0.52 ± 0.35 m a −1 on average and an overall mass loss of 0.46 ± 0.37 m w.e. a −1 . Highly variable individual glacier responses were observed and interestingly, they were less negative than previously reported for the neighboring Patagonian Icefields.

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In contrast to the large surge-type glacier clusters widely known for several mountain ranges around the world, the presence of surging glaciers in the Andes has been historically seen as marginal. The improved availability of satellite imagery during the last years facilitates investigating of glaciers in more detail even in remote areas. The purpose of the study was therefore to revisit existing information about surge-type glaciers for the Central Andes of Argentina and Chile (32° 40′–34° 20′ S), to identify and characterize possible further surge-type glaciers, providing new insights into the mass balance and evolution of the velocity of selected glaciers during the surge phase. Based on the analysis of 1962–2015 satellite imagery, historical aerial images, differencing of digital elevation models and a literature survey, we identified 21 surge-type glaciers in the study area. Eleven surge events and six possible surge-type glaciers were identified and described for the first time. The estimation of annual elevation changes of these glaciers for the 2000–2011 period, which encompasses the latest surge events in the region, showed heterogeneous behavior with strongly negative to positive surface elevation change patterns (−1.1 to +1.0 m yr−1). Additionally, we calculated maximum surface velocities of 3±1.9 m d−1 and 3.1±1.1 m d−1 for two of the glaciers during the latest identifiable surge events of 1985–1987 and 2003–2007. Within this glacier cluster, highly variable advance rates (0.01–1 km yr−1) and dissimilar surface velocities at the surge peak (3–35 m d−1) were observed. In comparison with other clusters worldwide, surge-type glaciers in the Central Andes are on average smaller and show minor absolute advances. Generally low velocities and the heterogeneous duration of the surge cycles are common between them and glaciers in the Karakorum, a region with similar climatic characteristics and many known surge-type glaciers. As a definitive assertion concerning the underlying surge mechanism of surges in the Central Andes could not be drawn based on the remote sensing data, this opens more detailed research avenues for surge-type glaciers in the region.

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<p>The object of this study aims to evaluate and analyze digital image processing techniques applied to the Enhanced Thematic Mapper Plus (ETM+), in order to demark and characterize the outcropping lithologies on the Upsala Glacier basin, Santa Cruz, Argentine Republic. The prolific technological and spatial development experienced in the last decades has given place to the generation, without precedents, of multiple remote sensors capable of capturing information of the terrestrial surface and also the improvement of digital image processing techniques and software; amongst them, the amazing possibilities in the detection and differentiation of diverse covers present on the terrestrial surface can be highlighted, such as glaciers, volcanoes, vegetation, soils, water, types of rock outcrops, etc. This situation improves mapping and monitoring of natural phenomenon in the Earth Sciences field. The proposed methodology includes radiometric corrections, elimination of unwanted covers, statistical evaluation in the combination of the most appropriate bands, application of the Z index, discretization of the statistical series, entailing tasks of spectral classification with field samples and a later validation. Valuable results were obtained by means of digital processing of images, that were validated yielding a 82% of accuracy in the proposed classification, which are good results taking into account the diversity of covers present and the lithological heterogeneity that makes up each pixel (30m). These results were also validated with existing geological maps, obtaining a good agreement.</p>

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ABSTRACT. In this study we present surface velocities estimation for the Upsala glacier catchment, South Patagonian Ice Field (SPI) during the summer season of years 2013 (January-March) and 2014 (March-April), including the Bertacchi, Cono, and Murallón tributaries using satellite images from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). The Cross-Correlation method was applied by COSI-Corr technique with sub-pixel accuracy. In general, it should be noted that the SPI glaciers, and Upsala glacier in particular, are fast-flowing ice bodies, which makes the technique works properly. Results of surface velocities estimation ranged from 0.22 to 2.93 md -1 for January-March 2013 and 0.12 to 5.8 md -1 for March-April 2014. In summary, COSI-Corr can achieved accurate and reliable results for glacier displacements and surface velocities estimation, also contributing in the better knowledge of the velocities change processes in time, taking into account Upsala is one of the most dynamic temperate glaciers of the SPI. RESUMEN. Velocidades superficiales del glaciar Upsala, Andes Patagónicos Sur, mediante el uso de correlación cruzada en imágenes satelitales: periodo 2013-2014. En este estudio se presentan las estimaciones de velocidades superficiales de la cuenca del glaciar Upsala, Campo de Hielo Patagónico Sur (CHPS) durante la temporada de verano de los años 2013 (enero-marzo) y 2014 (marzo-abril), incluyendo los glaciares tributarios Bertacchi, Cono y Murallón utilizando imágenes satelitales ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer). El método de correlación cruzada se aplicó mediante la implementación de la técnica COSI-Corr, con una precisión a nivel de subpixel. Cabe destacar que los glaciares del CHPS, en general, y el glaciar Upsala, en particular, son cuerpos de hielo de flujo rápido, lo que hace que la técnica funcione correctamente. Los resultados de las velocidades superficiales oscilaron entre 0,22 a 2,93 md -1 para el periodo enero-marzo de 2013 y de 0,12 a 5,8 md -1 para el periodo marzo-abril de 2014. En resumen, COSI-Corr alcanzó resultados precisos y confiables para la estimación de desplazamientos y velocidades superficiales de los glaciares, contribuyendo al mejor conocimiento de los procesos de cambio de velocidades en el tiempo, teniendo en cuenta que Upsala es uno de los glaciares templados más dinámicos del CHPS.