Luc Girod

• Aga, Juditha; Piermattei, Livia; Girod, Luc; Aalstad, Kristoffer; Eiken, Trond & Kääb, Andreas [Show all 7 contributors for this article] (2024). Acceleration of coastal-retreat rates for high-Arctic rock cliffs on Brøggerhalvøya, Svalbard, over the past decade. Earth Surface Dynamics. ISSN 2196-6311. 12(5), p. 1049–1070. doi: 10.5194/esurf-12-1049-2024. Full text in Research Archive Show summary

  In many Arctic regions, marine coastlines change rapidly in our currently warming climate. In contrast, coastal rock cliffs on Svalbard are considered to be relatively stable. Long-term trends of coastal-retreat rates for rock cliffs on Svalbard remain unknown, but quantifying them could improve our understanding of coastal dynamics in the Canadian Arctic Archipelago. This study presents coastal-retreat rates for rock cliffs along several kilometres of Brøggerhalvøya, Svalbard. The analysis relies on high-resolution orthoimages from 1970, 1990, 2010, and 2021. The data are corroborated by high-precision dGNSS (differential Global Navigation Satellite System) measurements obtained along selected segments of the coastline. Our analysis reveals statistically significant acceleration in coastal-retreat rates across Brøggerhalvøya between 2010 and 2021. The northeast-facing coastline features fairly stable conditions, with retreat rates of 0.04 ± 0.06 m a−1 (1970–1990; calculated retreat rate ± the corresponding measurement uncertainty), 0.04 ± 0.04 m a−1 (1990–2010), and 0.06 ± 0.08 m a−1 (2010–2021). Along the southwest-facing coastline, higher retreat rates of 0.26 ± 0.06 m a−1 (1970–1990), 0.24 ± 0.04 m a−1 (1990–2010), and 0.30 ± 0.08 m a−1 (2010–2021) were calculated. For the most recent decade, this corresponds to an increase of 50 % for the northeast-facing coastline and an increase of 25 % for the southwest-facing coastline. Furthermore, for the northeast-facing coastline, the proportion of the coastline affected by erosion increased from 47 % (1970–1990) to 65 % (2010–2021), while it stayed consistently above 90 % for the southwest-facing coastline. The recent acceleration in retreat rates coincides with increasing storminess and retreating sea ice, factors that can enhance coastal erosion.

• Kääb, Andreas & Girod, Luc (2023). Brief communication: Rapid ∼ 335 × 106 m3 bed erosion after detachment of the Sedongpu Glacier (Tibet). The Cryosphere. ISSN 1994-0416. 17(6), p. 2533–2541. doi: 10.5194/tc-17-2533-2023. Full text in Research Archive Show summary

  Following the 130 ± 5 × 106 m3 detachment of the Sedongpu Glacier, south-eastern Tibet, in October 2018, the Sedongpu Valley, which drains into the Yarlung Tsangpo (Brahmaputra) River, underwent rapid large-volume landscape changes. Between December 2018 and 2022 and in particular during summer 2021, an enormous volume of in total ∼ 335 ± 5 × 106 m3 was eroded from the former glacier bed, forming a new canyon of up to 300 m depth, 1 km width, and almost 4 km length. The 2021 erosion peak happened through massive but still gradual retrogressive erosion into the former glacier bed. Several rock–ice avalanches of in total ∼ 150 ± 5 × 106 m3 added to the total rock, sediment, and ice volume of over 600 × 106 m3 (0.6 km3) that has been exported from the basin since around 2017. The recent erosion volumes at Sedongpu are by order of magnitude equivalent to the average annual denudation volume of the entire Brahmaputra basin upstream of the location where the river leaves the Himalayas. This high-magnitude low-frequency event illustrates the potential for rapid post-glacial landscape evolution and associated hazards that has rarely been observed and considered at such high intensity so far.

• Paul, Frank; Piermattei, Livia; Treichler, Désirée; Gilbert, Lin; Girod, Luc & Kääb, Andreas [Show all 10 contributors for this article] (2022). Three different glacier surges at a spot: What satellites observe and what not. The Cryosphere. ISSN 1994-0416. 16(6), p. 2505–2526. doi: 10.5194/tc-16-2505-2022. Full text in Research Archive Show summary

  In the Karakoram, dozens of glacier surges occurred in the past two decades, making the region one of its global hot spots. Detailed analyses of dense time series from optical and radar satellite images revealed a wide range of surge behaviour in this region: from slow advances longer than a decade at low flow velocities to short, pulse-like advances over one or two years with high velocities. In this study, we present an analysis of three currently surging glaciers in the central Karakoram: North and South Chongtar Glaciers and an unnamed glacier referred to as NN9. All three glaciers flow towards the same region but differ strongly in surge behaviour. A full suite of satellite sensors and digital elevation models (DEMs) from different sources are used to (a) obtain comprehensive information about the evolution of the surges from 2000 to 2021 and (b) to compare and evaluate capabilities and limitations of the different satellite sensors for monitoring relatively small glaciers in steep terrain. A strongly contrasting evolution of advance rates and flow velocities is found, though the elevation change pattern is more similar. For example, South Chongtar Glacier had short-lived advance rates above 10 km y−1, velocities up to 30 m d−1 and surface elevations increased by 200 m. In contrast, the neighbouring and three times smaller North Chongtar Glacier had a slow and near linear increase of advance rates (up to 500 m y−1), flow velocities below 1 m d−1 and elevation increases up to 100 m. The even smaller glacier NN9 changed from a slow advance to a full surge within a year, reaching advance rates higher than 1 km y−1. It seems that, despite a similar climatic setting, different surge mechanisms are at play and a transition from one mechanism to another can occur during a single surge. The sensor inter-comparison revealed a high agreement across sensors for deriving flow velocities, but limitations are found on small and narrow glaciers in steep terrain, in particular for Sentinel-1. All investigated DEMs have the required accuracy to clearly show the volume changes during the surges and elevations from ICESat-2 ATL06 data fit neatly. We conclude that the available satellite data allow for a comprehensive observation of glacier surges from space when combining different sensors to determine the temporal evolution of length, elevation and velocity changes.

• Valk, Luuk D. Van Der; Teuling, Adriaan J.; Girod, Luc; Pirk, Norbert; Stoffer, Robin & Heerwaarden, Chiel C. Van (2022). Understanding wind-driven melt of patchy snow cover. The Cryosphere. ISSN 1994-0416. 16(10), p. 4319–4341. doi: 10.5194/tc-16-4319-2022. Full text in Research Archive Show summary

  Abstract. The representation of snow processes in most large-scale hydrological and climate models is known to introduce considerable uncertainty into the predictions and projections of water availability. During the critical snowmelt period, the main challenge in snow modeling is that net radiation is spatially highly variable for a patchy snow cover, resulting in large horizontal differences in temperatures and heat fluxes. When a wind blows over such a system, these differences can drive advection of sensible and latent heat from the snow-free areas to the snow patches, potentially enhancing the melt rates at the leading edge and increasing the variability of subgrid melt rates. To get more insight into these processes, we examine the melt along the upwind and downwind edges of a 50 m long snow patch in the Finseelvi catchment, Norway, and try to explain the observed behavior with idealized simulations of heat fluxes and air movement over patchy snow. The melt of the snow patch was monitored from 11 June until 15 June 2019 by making use of height maps obtained through the photogrammetric structure-from-motion principle. A vertical melt of 23 ± 2.0 cm was observed at the upwind edge over the course of the field campaign, whereas the downwind edge melted only 3 ± 0.4 cm. When comparing this with meteorological measurements, we estimate the turbulent heat fluxes to be responsible for 60 % to 80 % of the upwind melt, of which a significant part is caused by the latent heat flux. The melt at the downwind edge approximately matches the melt occurring due to net radiation. To better understand the dominant processes, we represented this behavior in idealized direct numerical simulations, which are based on the measurements on a single snow patch by Harder et al. (2017) and resemble a flat, patchy snow cover with typical snow patch sizes of 15, 30, and 60 m. Using these simulations, we found that the reduction of the vertical temperature gradient over the snow patch was the main cause of the reductions in vertical sensible heat flux over distance from the leading edge, independent of the typical snow patch size. Moreover, we observed that the sensible heat fluxes at the leading edge and the decay over distance were independent of snow patch size as well, which resulted in a 15 % and 25 % reduction in average snowmelt for, respectively, a doubling and quadrupling of the typical snow patch size. These findings lay out pathways to include the effect of highly variable turbulent heat fluxes based on the typical snow patch size in large-scale hydrological and climate models to improve snowmelt modeling.

• Kääb, Andreas; Jacquemart, Mylene; Gilbert, Adrien; Leinss, Silvan; Girod, Luc & Huggel, Christian [Show all 15 contributors for this article] (2021). Sudden large-volume detachments of low-angle mountain glaciers – more frequent than thought? The Cryosphere. ISSN 1994-0416. 15(4), p. 1751–1785. doi: 10.5194/tc-15-1751-2021. Full text in Research Archive
• Denzinger, Florian; Machguth, Horst; Barandun, Martina; Berthier, Etienne; Girod, Luc & Kronenberg, Marlene [Show all 8 contributors for this article] (2021). Geodetic mass balance of Abramov Glacier from 1975 to 2015. Journal of Glaciology. ISSN 0022-1430. 67(262), p. 331–342. doi: 10.1017/jog.2020.108. Full text in Research Archive Show summary

  Abstract Multi-decadal mass loss estimates are available for few glaciers of Central Asia. On Abramov Glacier (Pamir-Alay, Kyrgyzstan), comprehensive long-term glaciological measurements have been carried out from 1968 to 1999 and re-initiated in 2011. A climatological interpretation of this benchmark glacier in Central Asia requires bridging the gap between historical and renewed measurements. This is achieved here by computing the geodetic mass balance from 1975 to 2015 using previously unreleased Soviet aerial imagery and Pléaides stereo-imagery. During 1975–2015, Abramov Glacier lost 2.2 km 2 (8.2%) of its area. The mean annual thickness change was − 0.43 ± 0.14 m a −1 for the period 1975–2015, corresponding to a volume change of − 0.45 ± 0.15 km 3 . The average specific geodetic mass balance amounts to − 0.38 ± 0.12 m w . e . a −1 . The 1975–2015 glacier mass loss lies within the range of glaciological and geodetic mass-balance estimates that were previously published for disparate and shorter time intervals since 1968. This study covers a much longer time period than earlier geodetic estimates and demonstrates the capacity to geodetically constrain glacier change at high spatial resolution in Central Asia using historic aerial imagery and Structure from Motion techniques. Therefore, it could serve as a benchmark for future studies of regional mass change.

• Child, Sarah F.; Stearns, Leigh A; Girod, Luc Maurice Ramuntcho & Brecher, Henry H (2021). Structure-From-Motion Photogrammetry of Antarctic Historical Aerial Photographs in Conjunction with Ground Control Derived from Satellite Data. Remote Sensing. 13(1). doi: 10.3390/rs13010021. Full text in Research Archive Show summary

  A longer temporal scale of Antarctic observations is vital to better understanding glacier dynamics and improving ice sheet model projections. One underutilized data source that expands the temporal scale is aerial photography, specifically imagery collected prior to 1990. However, processing Antarctic historical aerial imagery using modern photogrammetry software is difficult, as it requires precise information about the data collection process and extensive in situ ground control is required. Often, the necessary orientation metadata for older aerial imagery is lost and in situ data collection in regions like Antarctica is extremely difficult to obtain, limiting the use of traditional photogrammetric methods. Here, we test an alternative methodology to generate elevations from historical Antarctic aerial imagery. Instead of relying on pre-existing ground control, we use structure-from-motion photogrammetry techniques to process the imagery with manually derived ground control from high-resolution satellite imagery. This case study is based on vertical aerial image sets collected over Byrd Glacier, East Antarctica in December 1978 and January 1979. Our results are the oldest, highest resolution digital elevation models (DEMs) ever generated for an Antarctic glacier. We use these DEMs to estimate glacier dynamics and show that surface elevation of Byrd Glacier has been constant for the past ∼40 years.

• Hugonnet, Romain; McNabb, Robert Whitfield; Berthier, Etienne; Menounos, Brian; Nuth, Christopher & Girod, Luc Maurice Ramuntcho [Show all 11 contributors for this article] (2021). Accelerated global glacier mass loss in the early twenty-first century. Nature. ISSN 0028-0836. 592, p. 726–731. doi: 10.1038/s41586-021-03436-z. Full text in Research Archive Show summary

  Glaciers distinct from the Greenland and Antarctic ice sheets are shrinking rapidly, altering regional hydrology1, raising global sea level2 and elevating natural hazards3. Yet, owing to the scarcity of constrained mass loss observations, glacier evolution during the satellite era is known only partially, as a geographic and temporal patchwork4,5. Here we reveal the accelerated, albeit contrasting, patterns of glacier mass loss during the early twenty-first century. Using largely untapped satellite archives, we chart surface elevation changes at a high spatiotemporal resolution over all of Earth’s glaciers. We extensively validate our estimates against independent, high-precision measurements and present a globally complete and consistent estimate of glacier mass change. We show that during 2000–2019, glaciers lost a mass of 267 ± 16 gigatonnes per year, equivalent to 21 ± 3 per cent of the observed sea-level rise6. We identify a mass loss acceleration of 48 ± 16 gigatonnes per year per decade, explaining 6 to 19 per cent of the observed acceleration of sea-level rise. Particularly, thinning rates of glaciers outside ice sheet peripheries doubled over the past two decades. Glaciers currently lose more mass, and at similar or larger acceleration rates, than the Greenland or Antarctic ice sheets taken separately7,8,9. By uncovering the patterns of mass change in many regions, we find contrasting glacier fluctuations that agree with the decadal variability in precipitation and temperature. These include a North Atlantic anomaly of decelerated mass loss, a strongly accelerated loss from northwestern American glaciers, and the apparent end of the Karakoram anomaly of mass gain10. We anticipate our highly resolved estimates to advance the understanding of drivers that govern the distribution of glacier change, and to extend our capabilities of predicting these changes at all scales. Predictions robustly benchmarked against observations are critically needed to design adaptive policies for the local- and regional-scale management of water resources and cryospheric risks, as well as for the global-scale mitigation of sea-level rise.

• Etzelmüller, Bernd; Patton, Henry; Schomacker, Anders; Czekirda, Justyna; Girod, Luc Maurice Ramuntcho & Hubbard, Alun Lloyd [Show all 8 contributors for this article] (2020). Icelandic permafrost dynamics since the Last Glacial Maximum – model results and geomorphological implications. Quaternary Science Reviews. ISSN 0277-3791. 233:106236. doi: 10.1016/j.quascirev.2020.106236. Full text in Research Archive Show summary

  Iceland’s periglacial realm is one of the most dynamic on the planet, with active geomorphologicalprocesses and high weathering rates of young bedrock resulting in high sediment yields and ongoingmass movement. Permafrost is discontinuous in Iceland’s highlands and mountains over c. 800 m a.s.l,and sporadic in palsa mires in the central highlands. During the late Pleistocene and Holocene, Iceland’speriglacial environment varied considerably in time and space, dominated by glacialfluctuations andperiglacial processes. To evaluate the dynamics of permafrost in Iceland since the last deglaciation, weuse the output of a coupled climate/ice sheet model to force a transient permafrost model (CryoGRID 2)from the Last Glacial Maximum (LGM) through to the present. Wefind that permafrost was widespreadacross the deglaciated areas of western, northern and eastern Iceland after the LGM, and that up to 20% ofIceland’s terrestrial area was underlain by permafrost throughout the late Pleistocene. This influencedgeomorphological processes and landform generation: the early collapse of the marine-based ice sheettogether with the aggradation of permafrost in these zones initiated the formation of abundant and nowrelict rock glaciers across coastal margins. Permafrost degraded rapidly after the Younger Dryas, with amarked impact on slope stability. Permafrost that formed during the Little Ice Age is again thawingrapidly, and an escalation in slope failure and mass-movement might be currently underway. Our studydemonstrates that large regions of Iceland have been underlain by permafrost for millennia, facilitatinglandform development and influencing the stability of steep slopes

• Girod, Luc Maurice Ramuntcho & Filhol, Simon Vincent P (2020). ABSOLUTE COREGISTRATION AND DOMING CORRECTION IN ADVERSE CONDITIONS, OR HOW TO RETRIEVE SNOW DEPTH FROM DRONE FLIGHTS. ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences. ISSN 2194-9042. V-3-2020, p. 375–379. doi: 10.5194/isprs-annals-V-3-2020-375-2020. Full text in Research Archive Show summary

  Doming, a superimposition of a scene-wide dome-shaped bias to the elevation data, is a classical problem in photogrammetry, especially when using the auto-calibration and bundle adjustment typical of the Structure-from-Motion approach. A number of solutions have been proposed, but most rely on a certain degree of freedom in the data acquisition strategy, such as the ability to acquire many ground control points or to acquire additional imagery over the area of interest with different flight parameters. In this paper, we present a method to solve for the dome when working on a snowfield in the Norwegian mountains. That specific situation leads to difficulties to fly the drone optimally and acquire ground control points due to short weather windows, high winds, cold temperatures, low sun angles and short day duration (i.e. high latitudes). Here, we use natural landmarks and pre-existing knowledge about the bare ground topography for removing the inevitable dome.

• Nuth, Christopher; Gilbert, Adrien; Köhler, Andreas; McNabb, Robert Whitfield; Schellenberger, Thomas & Sevestre, Heidi [Show all 10 contributors for this article] (2019). Dynamic vulnerability revealed in the collapse of an Arctic tidewater glacier. Scientific Reports. 9. doi: 10.1038/s41598-019-41117-0. Full text in Research Archive Show summary

  Glacier flow instabilities can rapidly increase sea level through enhanced ice discharge. Surge-type glacier accelerations often occur with a decadal to centennial cyclicity suggesting internal mechanisms responsible. Recently, many surging tidewater glaciers around the Arctic Barents Sea region question whether external forces such as climate can trigger dynamic instabilities. Here, we identify a mechanism in which climate change can instigate surges of Arctic tidewater glaciers. Using satellite and seismic remote sensing observations combined with three-dimensional thermo-mechanical modeling of the January 2009 collapse of the Nathorst Glacier System (NGS) in Svalbard, we show that an underlying condition for instability was basal freezing and associated friction increase under the glacier tongue. In contrast, continued basal sliding further upstream increased driving stresses until eventual and sudden till failure under the tongue. The instability propagated rapidly up-glacier, mobilizing the entire 450 km2 glacier basin over a few days as the till entered an unstable friction regime. Enhanced mass loss during and after the collapse (5–7 fold compared to pre-collapse mass losses) combined with regionally rising equilibrium line altitudes strongly limit mass replenishment of the glacier, suggesting irreversible consequences. Climate plays a paradoxical role as cold glacier thinning and retreat promote basal freezing which increases friction at the tongue by stabilizing an efficient basal drainage system. However, with some of the most intense atmospheric warming on Earth occurring in the Arctic, increased melt water can reduce till strength under tidewater glacier tongues to orchestrate a temporal clustering of surges at decadal timescales, such as those observed in Svalbard at the end of the Little Ice Age. Consequently, basal terminus freezing promotes a dynamic vulnerability to climate change that may be present in many Arctic tidewater glaciers.

• Filhol, Simon; Perret, Alexis; Girod, Luc Maurice Ramuntcho; Sutter, Guillaume; Schuler, Thomas & Burkhart, John (2019). Time-lapse photogrammetry of distributed snow depth during snowmelt. Water Resources Research. ISSN 0043-1397. 55(9), p. 7916–7926. doi: 10.1029/2018WR024530. Full text in Research Archive Show summary

  Characterizing snowmelt both spatially and temporally from in situ observation remains a challenge. Available sensors (i.e., sonic ranger, lidar, airborne photogrammetry) provide either time series of local point measurements or sporadic surveys covering larger areas. We propose a methodology to recover from a minimum of three synchronized time-lapse cameras changes in snow depth and snow cover extent over area smaller or equivalent to 0.12 km2 . Our method uses photogrammetry to compute point clouds from a set of three or more images and automatically repeat this task for the entire time series. The challenges were (1) finding an optimal experimental setup deployable in the field, (2) estimating the error associated with this technique, and (3) being able to minimize the input of manual work in the data processing pipeline. Developed and tested in the field in Finse, Norway, over 1 month during the 2018 melt season, we estimated a median melt of 2.12 ± 0.48 m derived from three cameras 1.2 km away from the region of interest. The closest weather station recorded 1.94 m of melt. Other parameters like snow cover extent and duration could be estimated over a 300 × 400m region. The software is open source and applicable to a broader range of geomorphologic processes like glacier dynamic, snow accumulation, or any other processes of surface deformation, with the conditions of (1) having fixed visible points within the area of interest and (2) resolving sufficient surface textures in the photographs.

• McNabb, Robert Whitfield; Nuth, Christopher; Kääb, Andreas & Girod, Luc Maurice Ramuntcho (2019). Sensitivity of glacier volume change estimation to DEM void interpolation. The Cryosphere. ISSN 1994-0416. 13(3), p. 895–910. doi: 10.5194/tc-13-895-2019. Full text in Research Archive Show summary

  Glacier mass balance has been estimated on individual glacier and regional scales using repeat digital elevation models (DEMs). DEMs often have gaps in coverage (“voids”), the properties of which depend on the nature of the sensor used and the surface being measured. The way that these voids are accounted for has a direct impact on the estimate of geodetic glacier mass balance, though a systematic comparison of different proposed methods has been heretofore lacking. In this study, we determine the impact and sensitivity of void interpolation methods on estimates of volume change. Using two spatially complete, high-resolution DEMs over southeast Alaska, USA, we artificially generate voids in one of the DEMs using correlation values derived from photogrammetric processing of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) scenes. We then compare 11 different void interpolation methods on a glacier-by-glacier and regional basis. We find that a few methods introduce biases of up to 20 % in the regional results, while other methods give results very close (<1 % difference) to the true, non-voided volume change estimates. By comparing results from a few of the best-performing methods, an estimate of the uncertainty introduced by interpolating voids can be obtained. Finally, by increasing the number of voids, we show that with these best-performing methods, reliable estimates of glacier-wide volume change can be obtained, even with sparse DEM coverage.

• McNabb, Robert Whitfield; Nuth, Christopher; Kääb, Andreas & Girod, Luc Maurice Ramuntcho (2018). Sensitivity of geodetic glacier mass balance estimation to DEM void interpolation. The Cryosphere Discussions. doi: 10.5194/tc-2018-175. Full text in Research Archive
• Girod, Luc Maurice Ramuntcho; Nielsen, Niels Ivar; Couderette, Frédérique; Nuth, Christopher & Kääb, Andreas (2018). Precise DEM extraction from Svalbard using 1936 high oblique imagery. Geoscientific Instrumentation, Methods and Data Systems. ISSN 2193-0856. 7, p. 277–288. doi: 10.5194/gi-7-277-2018. Full text in Research Archive Show summary

  Stretching time series further in the past with the best possible accuracy is essential to the understanding of climate change impacts and geomorphological processes evolving on decadal-scale time spans. In the first half of the twentieth century, large parts of the polar regions were still unmapped or only superficially so. To create cartographic data, a number of historic photogrammetric campaigns were conducted using oblique imagery, which is easier to work with in unmapped environments as collocating images is an easier task for the human eye given a more familiar viewing angle and a larger field of view. Even if the data obtained from such campaigns gave a good baseline for the mapping of the area, the precision and accuracy are to be considered with caution. Exploiting the possibilities arising from modern image processing tools and reprocessing the archives to obtain better data is therefore a task worth the effort. The oblique angle of view of the data is offering a challenge to classical photogrammetric tools, but the use of modern structure-from-motion (SfM) photogrammetry offers an efficient and quantitative way to process these data into terrain models. In this paper, we propose a good practice method for processing historical oblique imagery using free and open source software (MicMac and Python) and illustrate the process using images of the Svalbard archipelago acquired in 1936 by the Norwegian Polar Institute. On these data, our workflow provides 5 m resolution, high-quality elevation data (SD 2 m for moderate terrain) as well as orthoimages that allow for the reliable quantification of terrain change when compared to more modern data.

• Robson, Benjamin Aubrey; Nuth, Christopher; Nielsen, Pål Ringkjøb; Girod, Luc Maurice Ramuntcho; Hendrickx, Marijn & Dahl, Svein Olaf (2018). Spatial variability in patterns of glacier change across the Manaslu Range, Central Himalaya. Frontiers in Earth Science. 6. doi: 10.3389/feart.2018.00012. Full text in Research Archive Show summary

  This study assesses changes in glacier area, velocity, and geodetic mass balance for the glaciers in the Manaslu region of Nepal, a previously undocumented region of the Himalayas. We studied changes between 1970 (for select glaciers), 2000, 2005, and 2013 using freely available Landsat satellite imagery, the SRTM Digital Elevation Model (DEM) and a DEM based on Worldview imagery. Our results show a complex pattern of mass changes across the region, with glaciers lowering on average by 0.25 ± 0.08 m a^−1 between 2000 and 2013 which equates to a geodetic mass balance of −0.21 ± 0.16 m w.e.a^−1. Over approximately the same time period (1999 to 2013) the glaciers underwent a 16.0% decrease in mean surface velocity over their debris-covered tongues as well as a reduction in glacier area of 8.2%. The rates of glacier change appear to vary between the different time periods, with glacier losses increasing in most cases. The glaciers on Manaslu itself underwent a change in surface elevation of −0.46 ± 0.03 m a^−1 between 1970 and 2000 and −0.99 ± 0.08 m a^−1 between 2000 and 2013. Rates of glacier area change for the same glaciers increased from−0.36 km^2 a^−1 between 1970 and 2001 to −2.28 km^2 a^−1 between 2005 and 2013. Glacier change varies across the region and seems to relate to a combination of glacier hypsometry, glacier elevation range and the presence and distribution of supraglacial debris. Lower-elevation, debris-free glaciers with bottom-heavy hypsometries are losing most mass. As the glaciers in the Manaslu region continue to stagnate, an accumulation and thickening of the debris-cover is likely, thereby insulating the glacier and further complicating future glacier responses to climate.

• Girod, Luc Maurice Ramuntcho; Nuth, Christopher; Kääb, Andreas; McNabb, Robert Whitfield & Galland, Olivier (2017). MMASTER: Improved ASTER DEMs for elevation change monitoring. Remote Sensing. 9(7). doi: 10.3390/rs9070704. Full text in Research Archive Show summary

  The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) system on board the Terra (EOS AM-1) satellite has been a source of stereoscopic images covering the whole globe at 15-m resolution with consistent quality for over 16 years. The potential of these data in terms of geomorphological analysis and change detection in three dimensions is unrivaled and should be exploited more. Due to uncorrected errors in the image geometry due to sensor motion (“jitter”), however, the quality of the DEMs and orthoimages currently available is often insufficient for a number of applications, including surface change detection. We have therefore developed a series of algorithms packaged under the name MicMac ASTER (MMASTER). It is composed of a tool to compute Rational Polynomial Coefficient (RPC) models from the ASTER metadata, a method that improves the quality of the matching by identifying and correcting jitter-induced cross-track parallax errors and a correction for along-track jitter when computing differences between DEMs (either with another MMASTER DEM or with another data source). Our method outputs more precise DEMs with less unmatched areas and reduced overall noise compared to NASA’s standard AST14DMO product. The algorithms were implemented in the open source photogrammetric library and software suite MicMac. Here, we briefly examine the potential of MMASTER-produced DEMs to investigate a variety of geomorphological changes, including river erosion, seismic deformation, changes in biomass, volcanic deformation and glacier mass balance.

• Girod, Luc Maurice Ramuntcho; Nuth, Christopher; Kääb, Andreas; Etzelmüller, Bernd & Kohler, Jack (2017). Terrain changes from images acquired on opportunistic flights by SfM photogrammetry. The Cryosphere. ISSN 1994-0416. 11(2), p. 827–840. doi: 10.5194/tc-11-827-2017. Full text in Research Archive Show summary

  Acquiring data to analyse change in topography is often a costly endeavour requiring either extensive, potentially risky, fieldwork and/or expensive equipment or commercial data. Bringing the cost down while keeping the precision and accuracy has been a focus in geoscience in recent years. Structure from motion (SfM) photogrammetric techniques are emerging as powerful tools for surveying, with modern algorithm and large computing power allowing for the production of accurate and detailed data from low-cost, informal surveys. The high spatial and temporal resolution permits the monitoring of geomorphological features undergoing relatively rapid change, such as glaciers, moraines, or landslides. We present a method that takes advantage of light-transport flights conducting other missions to opportunistically collect imagery for geomorphological analysis. We test and validate an approach in which we attach a consumer-grade camera and a simple code-based Global Navigation Satellite System (GNSS) receiver to a helicopter to collect data when the flight path covers an area of interest. Our method is based and builds upon Welty et al. (2013), showing the ability to link GNSS data to images without a complex physical or electronic link, even with imprecise camera clocks and irregular time lapses. As a proof of concept, we conducted two test surveys, in September 2014 and 2015, over the glacier Midtre Lovénbreen and its forefield, in northwestern Svalbard. We were able to derive elevation change estimates comparable to in situ mass balance stake measurements. The accuracy and precision of our DEMs allow detection and analysis of a number of processes in the proglacial area, including the presence of thermokarst and the evolution of water channels.

• Girod, Luc Maurice Ramuntcho; Nuth, Christopher & Kääb, Andreas (2016). Glacier volume change estimation using time series of improved ASTER DEMs. International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences (ISPRS Archives). ISSN 1682-1750. 41(B8), p. 489–494. doi: 10.5194/isprsarchives-XLI-B8-489-2016. Full text in Research Archive
• Galland, Olivier; Bertelsen, Håvard Svanes; Guldstrand, Frank Bo Buster; Girod, Luc Maurice Ramuntcho; Johannessen, Rikke Færøvik & Bjugger, Fanny [Show all 8 contributors for this article] (2016). Application of open-source photogrammetric software MicMac for monitoring surface deformation in laboratory models. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 121(4), p. 2852–2872. doi: 10.1002/2015JB012564. Full text in Research Archive
• Girod, Luc Maurice Ramuntcho; Nuth, Christopher & Kääb, Andreas (2015). Improvement of DEM generation from ASTER images using satellite jitter estimation and open source implementation. International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences (ISPRS Archives). ISSN 1682-1750. 40(1), p. 249–253. doi: 10.5194/isprsarchives-XL-1-W5-249-2015. Full text in Research Archive
• Girod, Luc Maurice Ramuntcho & Pierrot-Deseilligny, Marc (2014). Égalisation radiométrique de nuages de points 3D issus de corrélation dense. Revue Francaise de Photogrammetrie et de Teledetection. ISSN 1768-9791. p. 3–14. Full text in Research Archive
• Kääb, Andreas; Girod, Luc Maurice Ramuntcho & Berthling, Ivar Thoralf (2014). Surface kinematics of periglacial sorted circles using structure-from-motion technology. The Cryosphere. ISSN 1994-0416. 8(3), p. 1041–1056. doi: 10.5194/tc-8-1041-2014. Full text in Research Archive Show summary

  Sorted soil circles are a form of periglacial patterned ground that is commonly noted for its striking geometric regularity. They consist of an inner fine domain bordered by gravel rings that rise some decimetres above the fine domain. Field measurements and numerical modelling suggest that these features develop from a convection-like circulation of soil in the active layer of permafrost. The related cyclic burial and exhumation of material is believed to play an important role in the soil carbon cycle of high latitudes. The connection of sorted circles to permafrost conditions and its changes over time make these ground forms potential palaeoclimatic indicators. In this study, we apply for the first time photogrammetric structure-from-motion technology (SfM) to large sets of overlapping terrestrial photos taken in August 2007 and 2010 over three sorted circles at Kvadehuksletta, western Spitsbergen. We retrieve repeat digital elevation models (DEMs) and orthoimages with millimetre resolution and precision. Changes in microrelief over the 3 yr are obtained from DEM differencing and horizontal displacement fields from tracking features between the orthoimages. In the fine domain, surface material moves radially outward at horizontal rates of up to ~2 cm yr-1. The coarse stones on the inner slopes of the gravel rings move radially inward at similar rates. A number of substantial deviations from this overall radial symmetry, both in horizontal displacements and in microrelief, shed new light on the spatio-temporal evolution of sorted soil circles, and potentially of periglacial patterned ground in general.

• Kääb, Andreas; Girod, Luc Maurice Ramuntcho & Berthling, Ivar Thoralf (2014). Surface kinematics of periglacial sorted circles using Structure-from-Motion technology. The Cryosphere Discussions. 7, p. 6043–6074. doi: 10.5194/tcd-7-6043-2013. Full text in Research Archive Show summary

  Sorted soil circles are a conspicuous form of periglacial patterned ground. Numerical modelling suggests that these features develop from a convection-like circulation of material in the active layer of permafrost. The related iterative burying and resurfacing of material is believed to play an important role in the soil carbon cycle of high latitudes. The connection of sorted circles to permafrost conditions and its changes over time make these ground forms to a potential paleoclimatic indicator. In this study we apply the photogrammetric Structure-from-Motion technology (SfM) to large sets of overlapping terrestrial photos taken in Augusts 2007 and 2010 over three sorted circles at Kvadehuksletta, Western Spitsbergen. We retrieve repeat digital elevation models (DEMs) and orthoimages with millimetre-resolution and accuracy. Changes in microrelief over the three years are obtained from DEM-differencing and horizontal displacement fields from tracking features between the orthoimages. In the inner domains of the circles, consisting of fines, material moves radially outside with horizontal surface speeds of up to 2 cm yr−1. The outer circle ridges consist of coarse stones that displace towards the inner circle domain at similar rates. A number of substantial deviations from this overall radial symmetry, both in horizontal displacements and in microrelief, shed new light on the potential spatio-temporal evolution of sorted soil circles, and periglacial patterned ground in general.

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• Andreassen, Liss Marie; Girod, Luc; Oldani, Simon & Marco, Jessica De (2026). Digitial surface models for Juvfonne 2016, 2023 and 2025. Full text in Research Archive
• Abderhalden, Jogscha Miriam; Andreassen, Liss Marie & Girod, Luc (2026). Ice thickness data Juvfonne 2025. Full text in Research Archive Show summary

  Ice thickness data for the ice patch Juvfonne collected in September 2025. See Andreassen et al. (2026) and Readme_icethickness_2025.txt for further details.

• Webster, Clare; Girod, Luc; Treichler, Desiree Silvana; Zweigel, Robin Benjamin & Westermann, Sebastian (2025). Measuring boreal forest and snow cover with UAV-lidar. Full text in Research Archive
• Treichler, Désirée; Mazzolini, Marco; Liu, Zhihao; Aune, Simen Dalseid; Bühler, Yves & Filhol, Simon [Show all 9 contributors for this article] (2025). Performance of high-resolution snow depth data from ICESat-2 spaceborne laser altimetry. Full text in Research Archive
• Treichler, Désirée; Mazzolini, Marco; Aune, Simen Dalseid; Bühler, Yves; Girod, Luc & Liu, Zhihao [Show all 8 contributors for this article] (2025). High-resolution snow depth profiles from ICESat-2. doi: https:/lps25.esa.int/lps25-presentations/presentations/316/_316.pdf. Full text in Research Archive Show summary

  To date, snow depth measurements require manual measurements or targeted field campaigns. The ATLAS sensor onboard the ICESat-2 satellite acquires profiles of surface elevation measurements of very high accuracy. When compared with an accurate digital elevation model (DEM) from snow-free conditions, this data directly translates into snow depth measurements. Previous studies used the spatially summarised ICESat-2 data products ATL06 and ATL08 with an along-profile resolution of 20-100 m. They found that ICESat-2 can provide average snow depth estimates at the watershed scale with decimeter-level uncertainties. Uncertainties and bias were found to strongly increase with slope and depend on the reference DEM accuracy and the quality of the co-registration of the datasets. This study uses the individual photon data product ATL03 that has an along-track resolution of 0.7 m and thus the potential to provide high-resolution snow depth profiles. Each overpass results in a profile pair separated by 90 m laterally and consisting of a weak and a strong beam with approximately four times as many return photons. We compare different photon filtering and co-registration methods for five field sites in Norway, Finland, and Switzerland including alpine terrain of different topography, sparse and dense forest. Given careful pre-processing, we find that ATL03 data can yield snow depth profiles with a few meters&#039; spatial resolution that closely match profiles derived from reference snow depth maps from uncrewed aerial vehicles (UAVs) acquired within 5-10 days of an ICESat-2 overpass. The goodness of fit depends on the chosen filtering method which should be adjusted to the acquisition conditions and the presence of vegetation and snow on trees to yield optimal results. Dataset co-registration is crucial for steep terrain, and in some areas, the strong and weak beam have different spatial offsets that require separate co-registration for each beam. Given locally optimised pre-processing, the uncertainty (mean absolute deviation, MAD) for ICESat-2/UAV data pairs ranges from 0.05 m in a sparsely forested, flat site to 0.4 m in a very steep alpine site. Bias (median residual) ranges from a few centimetres to several decimetres. For most sites the snow depths retrieved from strong and weak beams are consistently offset, with a vertical difference of up to 25 cm between strong/weak snow depth profiles for the same filtering/co-registration method and site, suggesting inconsistencies in the geolocation of beams of the same pair in ATL03 data. Improved low-level processing on the data provider&#039;s side in future ATL03 data versions may reduce the differences between the beams. This study finds that, given accurate reference DEMs, ICESat-2 data can not only provide catchment-scale snow depth averages but also high-resolution snow depth profiles in areas where no measurements currently exist, showcasing the potential of spaceborne laser altimetry for providing high-resolution snow depth measurements globally.

• Ignatiuk, Dariusz; Dunse, Thorben; Gallet, Jean-Charles; Girod, Luc; Kępski, Daniel & Laska, Michał [Show all 12 contributors for this article] (2023). Snow_GPR: Ground penetrating radar measurement of snow in Svalbard - past, present, future. In SIOS, SESS Report (Eds.), SESS report 2022. Svalbard Integrated Arctic Earth Observing System. ISSN 9788293871064. doi: 10.5281/zenodo.7371725. Full text in Research Archive
• Treichler, Désirée; Mazzolini, Marco; Piermattei, Livia; Webster, Clare; Girod, Luc & Aalstad, Kristoffer [Show all 7 contributors for this article] (2023). SNOWDEPTH: Spaceborne snow depth measurements from ICESat-2 laser altimetry and data assimilation. Full text in Research Archive
• Treichler, Désirée; Mazzolini, Marco; Piermattei, Livia; Webster, Clare; Girod, Luc & Bühler, Yves (2023). Spaceborne snow depth measurements from ICESat-2 laser altimetry. Full text in Research Archive
• Treichler, Désirée; Mazzolini, Marco; Piermattei, Livia; Webster, Clare & Girod, Luc (2022). Spaceborne snow depth measurements from ICESat-2 laser altimetry. Full text in Research Archive
• Huiban, Flora; Dømgaard, Mads; Girod, Luc; Millan, Roman; Dehecq, Amaury & Mouginot, Jeremie [Show all 9 contributors for this article] (2022). Expanding glacier time series of Antarctica and Greenland using Soviet Era KFA-1000 satellite images. EGU General Assembly. doi: 10.5194/egusphere-egu22-7374. Full text in Research Archive Show summary

  Long-term records of glaciers are more than ever crucial to understand their response to climate change. High-quality photogrammetric products, Digital Elevation Models (DEMs) and orthophotographs from early satellites are essential, as they offer a unique high-resolution view on the historical glacial dynamics. However, obtaining and producing high-resolution datasets from historical imagery can be a challenge. In our study, we are extending available satellite images time series using images from Soviet Era KFA-1000 satellite cameras. Each KFA-1000 has a 1000 mm objective, holding 1800 frames in its magazine. Each frame is typically 18x18 cm or 30 × 30 cm, with an 80 km swath width, providing panchromatic images. They supplement the very sparse data period between aerial images and high-resolution modern satellites, giving us high-resolution insight of Antarctica and Greenland dating from 1974 to 1994. Since these images have been largely underused, they have the potential to improve our knowledge of glaciers and open new scientific perspectives. They could help us improve models in studies regarding, for instance the frontal position, the flow-velocity (by doing feature tracking), the surface elevation or the grounding line of the glaciers, etc. With a spatial resolution up to 2 m and images recorded in stereo geometry, they offer a valuable complement to other historical satellite archives such as the declassified American KH imagery. Here, we use structure-from-motion (SfM) to reconstruct former glacier surfaces and flow of main outlet glaciers in both Antarctica and Greenland. We compare and assess the quality of the results by comparing the produced DEMs with recent high-resolution imagery from Worldview’s ArcticDEM. We combine the historical DEMs with recent satellite imagery of the ice elevation and reconstruct the comprehensive history of volume change over southeast and northeast Greenland glaciers since the 90s. Mostly lost from sight for 50 years, we are now resurrecting these highly valuable records and will make them freely available to science and the public.

• Child, Sarah F.; Scambos, Ted A; Fahnestock, M; Alley, Karen E; Stearns, Leigh A & Girod, Luc Maurice Ramuntcho (2020). Historical hypsometry analysis of the Dotson and Crosson Ice Shelves using trimetrogon aerial imagery with structure-from-motion processing techniques. Full text in Research Archive
• Alley, Karen E; Wild, Christian Thomas; Girod, Luc Maurice Ramuntcho; Luckman, Adrian; Child, Sarah F. & Hulen, Cyrus [Show all 12 contributors for this article] (2020). Two decades of dynamic changes on the Thwaites Eastern Ice Shelf. Full text in Research Archive
• Hugonnet, Romain; McNabb, Robert Whitfield; Berthier, Etienne; Menounos, B; Nuth, Christopher & Girod, Luc Maurice Ramuntcho [Show all 11 contributors for this article] (2020). Accelerated global glacier mass loss in the early twenty-first century. Full text in Research Archive
• Hugonnet, Romain; McNabb, Robert Whitfield; Berthier, Etienne; Menounos, B.; Nuth, Christopher & Girod, Luc Maurice Ramuntcho [Show all 11 contributors for this article] (2020). A globally complete, spatially and temporally resolved estimate of glacier mass change: 2000 to 2019. Full text in Research Archive
• McNabb, Robert Whitfield; Girod, Luc Maurice Ramuntcho; Nuth, Christopher & Kääb, Andreas (2020). An open-source toolset for automated processing of historic spy photos: sPyMicMac. Full text in Research Archive
• Girod, Luc Maurice Ramuntcho; Nielsen, Niels Ivar; Couderette, Frédérique; Hoslt, Marion Dominique; Lazizi, Laetitia Alice & Nuth, Christopher [Show all 7 contributors for this article] (2018). Extraction of glacier thickness change data and communication material from historical oblique imagery. Full text in Research Archive
• Galland, Olivier; Bertelsen, Håvard Svanes; Guldstrand, Frank Bo Buster; Girod, Luc Maurice Ramuntcho; Johannessen, Rikke F. & Bjugger, Fanny [Show all 8 contributors for this article] (2017). Application of open-source photogrammetric software MicMac for geodetic monitoring in laboratory models. Full text in Research Archive
• Galland, Olivier; Bertelsen, Håvard Svanes; Guldstrand, Frank Bo Buster; Girod, Luc Maurice Ramuntcho; Johannessen, Rikke Færøvik & Bjugger, Fanny [Show all 8 contributors for this article] (2017). Application of open-source photogrammetric software MicMac for geodetic monitoring in laboratory models. Full text in Research Archive
• Kääb, Andreas; Treichler, Désirée Silvana; Girod, Luc Maurice Ramuntcho; Lefeuvre, Pierre-Marie; Schellenberger, Thomas & Altena, Bas [Show all 10 contributors for this article] (2016). On the Karakoram anomaly. Full text in Research Archive
• Kääb, Andreas; Girod, Luc Maurice Ramuntcho & Berthling, Ivar Thoralf (2016). Surface kinematics of periglacial sorted circles over 8 years using SfM close range photogrammetry. Full text in Research Archive
• Girod, Luc Maurice Ramuntcho; Kääb, Andreas & Berthling, Ivar Thoralf (2016). Surface kinematics of periglacial sorted circles over 8 years using SfM close-range photogrammetry. Full text in Research Archive
• Girod, Luc Maurice Ramuntcho; Nuth, Christopher & Kääb, Andreas (2016). Opportunistic survey of glaciers using GoPros and helicopters. Full text in Research Archive
• Girod, Luc Maurice Ramuntcho; Nuth, Christopher & Kääb, Andreas (2016). Glacier volume change estimation using time series of improved ASTER DEMs. Full text in Research Archive
• Girod, Luc Maurice Ramuntcho; Couderette, Frédérique; Aas, Harald Faste & Nuth, Christopher (2016). Historical oblique images of Svalbard : DEM of the Archipelago's glaciers in 1936. Full text in Research Archive
• Girod, Luc Maurice Ramuntcho; Nuth, Christopher & Kääb, Andreas (2016). Enhanced ASTER DEMs for Decadal Measurments of Glacier Elevation Changes. Full text in Research Archive
• Nuth, Christopher; Girod, Luc Maurice Ramuntcho; Kohler, Jack; Bahr, Kenneth & Karlsen, Tor Ivan (2016). Detailed glacier crevasse morphology mapped by helicopter. Full text in Research Archive
• Girod, Luc Maurice Ramuntcho; Nuth, Christopher; Kääb, Andreas; Etzelmüller, Bernd & Kohler, Jack (2016). Terrain changes from images acquired on opportunistic flights by SFM photogrammetry. Full text in Research Archive
• Nuth, Christopher; Girod, Luc Maurice Ramuntcho; Winsvold, Solveig Havstad; Berger, Cesar Deschamps; Berthier, Etienne & Kääb, Andreas (2016). Remote Sensing in Ny Ålesund: Products, purpose and validation. Full text in Research Archive
• Galland, Olivier; Bertelsen, Håvard Svanes; Guldstrand, Frank Bo Buster; Girod, Luc Maurice Ramuntcho; Johannessen, Rikke Færøvik & Bjugger, Fanny [Show all 8 contributors for this article] (2016). Laboratory geodesy: Application of open-source photogram-metric software MicMac to monitoring surface deformation in laboratory models. Full text in Research Archive
• Galland, Olivier; Bertelsen, Håvard Svanes; Guldstrand, Frank Bo Buster; Girod, Luc Maurice Ramuntcho; Johannessen, Rikke Færøvik & Bjugger, Fanny [Show all 8 contributors for this article] (2016). Laboratory geodesy : Application of open-source photogrammetric software MicMac for monitoring surface deformation in laboratory models. Full text in Research Archive
• Girod, Luc Maurice Ramuntcho; Gautrais, Olivia; Nuth, Christopher & Kohler, Jack (2015). Structure from motion: a low cost, very high resolution method for surveying glaciers. Full text in Research Archive
• Girod, Luc Maurice Ramuntcho; Nuth, Christopher & Schellenberger, Thomas (2014). Structure from motion, a low cost, very high resolution method for surveying glaciers using GoPros and opportunistic helicopter flights. Full text in Research Archive
• Girod, Luc Maurice Ramuntcho (2018). Improved measurements of cryospheric processes using advanced photogrammetry. Universitetet i Oslo. Full text in Research Archive Show summary

  The cryosphere is defined as the areas of the Earth where water is found frozen. The notion of cryospheric processes relates to glaciers, ice caps, ice sheets, ice shelves, sea ice and permafrost. Cryospheric processes are often used as indicators of a changing climate since they respond relatively fast to climate change: sea ice extent decreases, ice shelves and glaciers retreat, permafrost thaws...Therefore, understanding these processes is critical to the understanding of the causes and effects of climate change. Photogrammetry, the science of making geometric and radiometric measurements using photographic imagery, has a century-long history of providing data for geoscience research. Indeed, it is an incredible tool to produce data for the study of processes of interest, in the form of digital elevation models to study their geometry, or in the form of orthoimages to study their texture. If imagery data of the same scene can be acquired at different moments in time, it is possible to create time series. Series of measurements allows for the study and understanding of the evolution of a process through time. This thesis presents work done in the development and application of leading edge photogrammetric methods to the measurement of cryopsheric processes, going through the different scales at which these processes are active, starting at the largest scale with the camera closest to the ground for the study of the meter scale and gradually getting a larger view. Close range photogrammetry was used for the study of the meter scale permafrost process of sorted circles, light airborne imaging was used for the study of a small glacier called Midtre Lovénbreen and its periglacial area, historical heavy airborne survey was used for a more regional survey of Prins Karl Forland and a satellite imaging processing workflow was developed to allow for the study of global scale changes. Thanks to recent developments in photogrammetry, including those presented in this thesis, data quality is on the rise. The key conclusions of this work are that (1) it is possible to push the limit of the precision of the elevation data obtained from imagery by applying modern, improved methods, and (2) that, with these methods, all sorts of image sources can be exploited in order to acquire data on various processes of interest. We used images that we acquired ourselves using consumer grade tools, images found by digging through historical airborne survey archives, and images obtained using spaceborne instruments. That second objective is complemented with the open-source availability of the software and methods developed in the context of this PhD in order to facilitate their use by the scientific community.

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