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Despite their extreme elevation, glaciers on the Tibetan Plateau are losing mass in response to atmospheric warming, the pattern of which purportedly reflects regional contrasts in climate. Here we examine the evolution of glaciers along ~500 km of the Tanggula Shan, Central-Eastern Tibetan Plateau. Using remotely sensed datasets, we quantified changes in glacier mass, area and surface velocity, and compared these results to time series of meteorological observations, in order to disentangle drivers of glacier mass loss since the 1960s. Glacier mass loss has increased (from −0.21 ± 0.12 m w.e. a−1 in 1960s–2000s, to −0.52 ± 0.18 m w.e. a−1 in 2000s–2015/18) in association with pervasive positive temperature anomalies (up to 1.85°C), which are pronounced at the end of the now lengthened ablation season. However, glacier mass budget perturbations do not mirror the magnitude of temperature anomalies in sub-regions, thus additional factors have heightened glacier recession. We show how proglacial lake expansion and glacier surging have compounded glacier recession over decadal/multi-decadal time periods, and exert similar influence on glacier mass budgets as temperature changes. Our results demonstrate the importance of ice loss mechanisms not often incorporated into broad-scale glacier projections, which need to be better considered to refine future glacier runoff estimates. [ABSTRACT FROM AUTHOR]

The panoramic cameras (PCs) on board Hexagon KH-9 (KH-9PC) satellite missions from 1971–1984 captured very high-resolution stereo imagery with up to 60 cm spatial resolution. This study explores the potential of this imagery for glacier mapping and change estimation. We assess KH-9PC imagery using data from the KH-9 mapping camera (KH-9MC), KH-4PC, and SPOT and Pléiades satellite imagery. The high resolution of KH-9PC leads to higher-quality DEMs, which better resolve the accumulation region of the glaciers in comparison to the KH-9MC. On stable terrain, KH-9PC DEMs achieve an elevation accuracy of <4 m with respect to SPOT and Pléiades DEMs. While the estimated geodetic mass balances using PC and MC data are similar after outlier filtering, the elevation change data show superior spatial coverage and considerably less noise when using KH-9PC data. [ABSTRACT FROM AUTHOR]

Knowledge about the occurrence and characteristics of surge-type glaciers is crucial due to the impact of surging on glacier melt and glacier-related hazards. One of the super-clusters of surge-type glaciers is High Mountain Asia (HMA). However, no consistent region-wide inventory of surge-type glaciers in HMA exists. We present a regionally resolved inventory of surge-type glaciers based on their behaviour across High Mountain Asia between 2000 and 2018. We identify surge-type behaviour from surface velocity, elevation and feature change patterns using a multi-factor remote sensing approach that combines yearly ITS_LIVE velocity data, DEM differences and very-high-resolution imagery (Bing Maps, Google Earth). Out of the ≈95000 glaciers in HMA, we identified 666 that show diagnostic surge-type glacier behaviour between 2000 and 2018, which are mainly found in the Karakoram (223) and the Pamir regions (223). The total area covered by the 666 surge-type glaciers represents 19.5 % of the glacierized area in Randolph Glacier Inventory (RGI) V6.0 polygons in HMA. Only 68 glaciers were already identified as "surge type" in the RGI V6.0. We further validate 107 glaciers previously labelled as "probably surge type" and newly identify 491 glaciers, not previously reported in other inventories covering HMA. We finally discuss the possibility of self-organized criticality in glacier surges. Across all regions of HMA, the surge-affected area within glacier complexes displays a significant power law dependency with glacier length. [ABSTRACT FROM AUTHOR]

Planet Labs have recently launched a large constellation of small satellites (3U cubesats) capable of imaging the whole Earth landmass everyday. These small satellites capture multiple images of an area on consecutive days or sometimes on the same day with a spatial resolution of 3–4 m. Planet Labs endeavors to operate the constellation in a nadir pointing mode, however, the view angle of these satellites currently varies within a few degrees from the nadir leading to varying B/H ratio for overlapping image pairs. Due to relatively small scene footprint and small off-nadir angle, the baseline to height ratio (B/H) of the overlapping PlanetScope images is often less than 1:10, which is not ideal for 3D reconstruction. Therefore, this paper explores the potential of Digital Elevation Model generation from this multi-date, multi-satellite PlanetScope imagery. The DEM generation from multiple PlanetScope images is achieved using a volumetric stereo reconstruction technique, which applies semi global matching in georeferenced object space. The results are evaluated using a LiDAR based DEM (5 m) over Mount Teide (3718 m) in Canary Islands and the ALOS (30 m) DEM on rugged terrain of the Nanga Parbat massif (8126 m) in the western Himalaya range. The proposed methodology is then applied on images from two PlanetScope satellites overpasses within a couple of minutes difference to compute the DEM of the Khurdopin glacier in the Karakoram range, known for its recent surge. The quantitative assessment of the generated elevation models is done by comparing statistics of the elevation differences between the reference LiDAR and ALOS DEM and the PlanetScope DEM. The Normalized Median of Absolute Deviation (NMAD) of the elevation differences between the computed PlanetScope DEM and LiDAR DEM is 4.1 m and the elevation differences for the ALOS DEM over stable terrain is 3.9 m. The results show that PlanetScope imagery can lead to sufficient quality DEM even with a small baseline to height ratio. Therefore, the daily PlanetScope imagery is a valuable data source and the DEM generated from this imagery can potentially be employed in numerous applications requiring multi temporal DEMs. [ABSTRACT FROM AUTHOR]