Variabilidad espectral y de la temperatura de superficie de los glaciares de la región del Khumbu (Himalayas centrales).

En el presente trabajo se ha llevado a cabo un estudio sobre la dinámica glaciar, tanto de glacia-res blancos como glaciares negros, en base a las imágenes del satélite Landsat entre 1987 y 2018, y asociarla a la dinámica climática. La zona de estudio seleccionada corresponde a la re-gión del Khumbu (más concretamente sobre los glaciares Khumbu, Nuptse, Changri, Chola, Ama-dablam e Imja), situada en los Himalayas centrales, es una de las zonas montañosas que alcan-zan mayores alturas en la Tierra. Presenta condiciones hacen que la climatología sea fría, permi-tiendo el desarrollo de los procesos glaciares y periglaciares. Esta zona está compuesta por rocas principalmente ígneas y metamórficas dominando los granitos y gneises y cubierta en su mayoría por los glaciares y sus depósitos morrénicos. No existen estudios de esta temática todavía, pero sí otros que se desarrollan en esta misma zo-na o que emplean las mismas técnicas. A partir de los datos de reflectividad de las imágenes Landsat se han generado las firmas espectrales de las diferentes cubiertas para los distintos años que abarca el estudio, observándose un patrón claro de disminución de la reflectividad con el pa-so del tiempo. Por otro lado, tras un tratamiento de las imágenes de la banda del térmico de este mismo satélite se han calculo las temperaturas de superficie (LST) de los distintos glaciares, ob-teniéndose valores de entre -17ºC a 7ºC, y en todos los casos se aprecia un incremento de LST a lo largo de los años.<br /

Geomorfología del macizo de Eriste: cálculo de paleoELAs y consideraciones paleoambientales

El maciczo de Eriste se localiza en los Pirineos, entre las poblaciones de Plan (Sobrarbe) y Eriste (Ribagorza) y los macizos de Llardana (3.369 m) y Cotiella (2.912 m). El modelado de este macizo está controlado principalmente por la litología. Los granitos generan relieves escarpados, las pizarras relieves más tendidos y en las calizas se desarrollan procesos kársticos. Tras la deglaciación las laderas pierden confinamiento, desarrollándose deslizamientos, sakungs y debris flows. La condiciones climáticas favorecen el desarrollo del modelado periglaciar, siendo los canchales la morfología más abundante. Durante la Pequeña Edad de Hielo, el macizo de Eriste tenía tres glaciares con orientación N, seis con orientación S, tres con orientación W y cuatro con orientación E. La mayor concentración de morrenas de la PEH se concentran en los circos de Bagüeña. Se han detectado dos fases glaciares en la PEH, asociadas al máximo de este periodo (1600-1750) y otra fase menor entre 1905-1920. Los resultados del cálculo de paleoELAs (con un gradiente altitudinal de -0.6ºC/100m y una ELA a 3.100 m) son de 2.685 m y un incremento de temperatura 2,48ºC

Intercomparison of UAV platforms for mapping snow depth distribution in complex alpine terrain

[EN]Unmanned Aerial Vehicles (UAVs) offer great flexibility in acquiring images in inaccessible study areas, which are then processed with stereo-matching techniques through Structure-from-Motion (SfM) algorithms. This procedure allows generating high spatial resolution 3D point clouds. The high accuracy of these 3D models allows the production of detailed snow depth distribution maps through the comparison of point clouds from different dates. In this way, UAVs allow monitoring of remote areas that were not achievable previously. The large number of works evaluating this novel technique has not, to date, conducted a systematic evaluation of concurrent snowpack observations with different UAV devices. Taking into account this, and also bearing in mind that potential users of this technique may be interested in exploiting ready-to-use commercial devices, we conducted an evaluation of the snow depth distribution maps with different commercial UAVs. During the 2018-19 snow season, two multi-rotors (Parrot Anafi and DJI Mavic Pro2) and one fixed-wing device (SenseFly eBee plus) were used on three different dates over a small test area (5 ha) within Izas Experimental Catchment in the Central Pyrenees. Simultaneously, snowpack distribution was retrieved with a Terrestrial Laser Scanner (TLS, RIEGL LPM-321) and was considered as ground truth. Three different georeferencing methods (Ground Control Points, ICP algorithm over snow-free areas and RTK-GPS positioning) were tested, showing equivalent performances under optimum illumination conditions. Additionally, for the three acquisition dates, both multi-rotors were flown at two distinct altitudes (50 and 75 m) to evaluate impact on the obtained snow depth maps. The evaluation with the TLS showed an equivalent performance of the two multi-rotors, with mean RMSE below 0.23 m and maximum volume deviations of less than 5%. Flying altitudes did not show significant differences in the obtained maps. These results were obtained under contrasted snow surface characteristics. This study reveals that under good illumination conditions and in relatively small areas, affordable commercial UAVs provide reliable estimations of snow distribution compared to more sophisticated and expensive close-range remote sensing techniques. Results obtained under overcast skies were poor, demonstrating that UAV observations require clear-sky conditions and acquisitions around noon to guarantee a homogenous illumination of the study area.This work was supported by the research projects of the Spanish Ministry of Economy and Competitiveness projects "El papel de la nieve en la hidrologia de la peninsula iberica y su respuesta a procesos de cambio global-CGL2017-82216-R" and the JPI-Climate co-funded call of the European Commission and INDECIS and CROSSDRO which are part of ERA4CS, and ERA-NET. Authors do not have any conflict of interest.). J. Revuelto is supported by a "Juan de la Cierva Incorporacion" postdoctoral fellow of the Spanish Ministry of Science, Innovation and Universities (Grant IJC2018-036260-I). I. Vidaller is supported by the Grant FPU18/04978 and is studying in the PhD program in the University of Zaragoza (Earth Science Department)

Toward an Ice-Free Mountain Range: Demise of Pyrenean Glaciers During 2011-2020

[EN]Pyrenean glaciers are the largest in southern Europe. Their survival is threatened by climate change, highlighting the significance of their study. This research presents an assessment of changes in the glacierized area and thickness of Pyrenean glaciers from 2011 to 2020, using high-resolution optical satellite, airborne lidar and UAV images. The total glacierized area has shrunk by 23.2% and thickness has decreased on average by 6.3 m. These two variables show no correlation for individual glaciers. Although climatic conditions do not vary much among glaciers, their evolution was heterogeneous during the study period. The smaller glaciers (10 ha) have a more homogeneous response. This can be attributed to the generally larger influence of local topography on the response of the smaller Pyrenean glaciers. There is no sign of slowdown in glacier shrinkage respect to previous decades.This work was supported by the Interreg-POCTEFA project OPCC ADAPYR and Spanish Ministry of Economy and Competitiveness project "CGL2017-82216-R." J. Revuelto is supported by the Grant IJC2018-036260-I. I. Vidaller is supported by the Grant FPU18/04978 and is studying the PhD program in the University of Zaragoza. E. Izagirre and I. Rico are supported by the Grant PPGI19/02 (UPV/EHU) and the Consolidated Research Group IT1029-16 (Basque Country Government). E. Berthier acknowledges support from the French Space Agency (CNES)