Papers by Antoine Rabatel
The EGU General Assembly, 2007
A significant number of rock avalanches (> several thousands of m) on high mountain rock walls... more A significant number of rock avalanches (> several thousands of m) on high mountain rock walls affected by permafrost has been documented during the last decade (e.g. Brenva Glacier, Italy, 1997; Mc Ginnis Peak, Alaska, 2002; Kolka-Karmadon, North Ossetia, 2002; Punta Thurwieser, Italy, 2004). In the Mont Blanc massif, the Petit Dru western face (3733 m a.s.l.) was affected by a series of events with increasing magnitude (1950, 1997, 2003) until 2005, when the largest rock avalanches (> 250,000 m in total) occurred. This increase is probably related to permafrost degradation, as a consequence of the climatic change associated to the global warming observed during the last decades.
L'usage des methodes de datation classiques en geomorphologie (radiocarbone, lichenometrie, s... more L'usage des methodes de datation classiques en geomorphologie (radiocarbone, lichenometrie, sediments lacustres) a permis de reconstruire l'evolution de glaciers des Andes intertropicales (du Venezuela a la Bolivie) au cours du dernier millenaire. Une premiere avancee glaciaire aux 13 eme /14 eme siecles a ete documentee sur certains glaciers. Cependant, la periode d'extension maximale (PEM) est plus tardive. Elle date de la periode 1630-1680 AD pour la zone intertropicale externe et d'environ 1730 AD pour la zone interne. Suite a ce maximum, un retrait glaciaire est observe pour l'ensemble de la zone, entrecoupe de quelques periodes de stagnation des fronts, ou de reavancees n'ayant cependant jamais eu une ampleur similaire a la PEM. L'interpretation paleoclimatique des resultats, construite a partir d'une modelisation climat/glacier, montre que la PEM serait la consequence de conditions plus froides et humides que l'actuel. Le retrait glaciaire ...
L’etude des processus glaciaires necessite un suivi de terrain pour comprendre les interactions e... more L’etude des processus glaciaires necessite un suivi de terrain pour comprendre les interactions entre les glaciers et leur environnement a des echelles fines de temps et d’espace. Un petit nombre de glaciers de reference est instrumente dans differentes regions climatiques a l’echelle mondiale, permettant un suivi de leur bilan de masse et dans certains cas de leur bilan d’energie de surface. Cependant, ce petit nombre constitue un obstacle a la connaissance de la relation entre les changements climatiques et l’evolution des glaciers a l’echelle d’un massif ou d’une region climatique. Il en est de meme pour la quantification de la contribution des glaciers aux ressources en eau et au fonctionnement des bassins versants de haute altitude. Ainsi, aboutir a une prise en compte des processus et des changements glaciaires a l’echelle regionale necessite un changement d’approche, et la teledetection s’avere etre l’outil le plus approprie. Ce suivi a plusieurs niveaux est la strategie mise...
The EGU General Assembly, 2008
International Journal of Climatology
Ecography
Retreating glaciers, icons of climate change, release new potential habitats for both aquatic and... more Retreating glaciers, icons of climate change, release new potential habitats for both aquatic and terrestrial organisms. High-elevation species are threatened by temperature increases and the upward migration of lowlands species. Improving our understanding of successional processes after glacier retreat becomes urgent, especially in the tropics, where glacier shrinkage is particularly fast. We examined the successional patterns of aquatic invertebrates, ground beetles, terrestrial plants, soil eukaryotes (algae, invertebrates, plants) in an equatorial glacier foreland (Carihuairazo, Ecuador). Based on both taxonomical identification and eDNA metabarcoding, we analysed the effects of both environmental conditions and age of deglacierization on community composition. Except for algae, diversity increased with time since deglacierization, especially among passive dispersers, suggesting that dispersal was a key driver structuring the glacier foreland succession. Spatial β-diversity was mainly attributed to nestedness for aquatic invertebrates, terrestrial plants and soil algae, likely linked to low environmental variability within the studied glacier foreland; and to turnover for soil invertebrates, suggesting competition exclusion at the oldest successional stage. Pioneer communities were dominated by species exhibiting flexible feeding strategies and high dispersal ability (mainly transported by wind), probably colonising from lower altitudes, or from the glacier in the case of algae. Overall, glacier foreland colonisation in the tropics exhibit common characteristics to higher latitudes. High-elevation species are nevertheless threatened, as the imminent extinction of many tropical glaciers will affect
The Cryosphere
Mass balance observations are very useful to assess climate change in different regions of the wo... more Mass balance observations are very useful to assess climate change in different regions of the world. As opposed to glacier-wide mass balances which are influenced by the dynamic response of each glacier, point mass balances provide a direct climatic signal that depends on surface accumulation and ablation only. Unfortunately, major efforts are required to conduct in situ measurements on glaciers. Here, we propose a new approach that determines point surface mass balances from remote sensing observations. We call this balance the geodetic point surface mass balance. From observations and modelling performed on the Argentière and Mer de Glace glaciers over the last decade, we show that the vertical ice flow velocity changes are small in areas of low bedrock slope. Therefore, assuming constant vertical velocities in time for such areas and provided that the vertical velocities have been measured for at least 1 year in the past, our method can be used to reconstruct annual point surface mass balances from surface elevations and horizontal velocities alone. We demonstrate that the annual point surface mass balances can be reconstructed with an accuracy of about 0.3 m of water equivalent per year (m w.e. a −1) using the vertical velocities observed over the previous years and data from unmanned aerial vehicle images. Given the recent improvements of satellite sensors, it should be possible to apply this method to high-spatial-resolution satellite images as well.
The ongoing glacier shrinkage in the Alps requires frequent updates of glacier outlines to provid... more The ongoing glacier shrinkage in the Alps requires frequent updates of glacier outlines to provide an accurate database for monitoring, modelling purposes (e.g. determination of runoff , mass balance, or future glacier extent), and other applications. With the launch of the first Sentinel-2 (S2) satellite in 2015, it became possible to create a consistent, Alpine-wide glacier inventory with an unprecedented spatial resolution of 10 m. The first S2 images from August 2015 already provided excellent mapping conditions for most glacierized regions in the Alps and were used as a base for the compilation of a new Alpine-wide glacier inventory in a collaborative team effort. In all countries, glacier outlines from the latest national inventories have been used as a guide to compile an update consistent with the respective previous interpretation. The automated mapping of clean glacier ice was straightforward using the band ratio method, but the numerous debris-covered glaciers required intense manual editing. Cloud cover over many glaciers in Italy required also including S2 scenes from 2016. The outline uncertainty was determined with digitizing of 14 glaciers several times by all participants. Topographic information for all glaciers was obtained from the ALOS AW3D30 digital elevation model (DEM). Overall, we derived a total glacier area of 1806 ± 60 km 2 when considering 4395 glaciers > 0.01 km 2. This is 14 % (−1.2 % a −1) less than the 2100 km 2 derived from Landsat in 2003 and indicates an unabated continuation of glacier shrinkage in the Alps since the mid-1980s. It is a lower-bound estimate, as due to the higher spatial resolution of S2 many small glaciers were additionally mapped or increased in size compared to 2003. Median elevations peak around 3000 m a.s.l., with a high variability that depends on location and aspect. The uncertainty assessment revealed locally strong differences in interpretation of debris-covered glaciers, resulting in limitations for change assessment when using glacier extents digitized by different analysts. The inventory is available at
La Météorologie
Des modelisations ont ete realisees sur les deux plus grands glaciers des Alpes francaises afin d... more Des modelisations ont ete realisees sur les deux plus grands glaciers des Alpes francaises afin d'estimer leur evolution au cours du XXI e siecle. Pour un scenario climatique intermediaire avec reduction des emissions de gaz a effet de serre avant la fin du XXI e siecle (RCP 4.5), les simulations indiquent que le glacier d'Argentiere devrait disparaitre vers la fin du XXI e siecle et que la surface de la Mer de Glace pourrait diminuer de 80 %. Dans l'hypothese la plus pessimiste d'une croissance ininterrompue des emissions de gaz a effet de serre (RCP 8.5), la Mer de Glace pourrait disparaitre avant 2100 et le glacier d'Argentiere une vingtaine d'annees plus tot.
The Cryosphere
Less than 0.25 % of the 250 000 glaciers inventoried in the Randolph Glacier Inventory (RGI V.5) ... more Less than 0.25 % of the 250 000 glaciers inventoried in the Randolph Glacier Inventory (RGI V.5) are currently monitored with in situ measurements of surface mass balance. Increasing this archive is very challenging, especially using time-consuming methods based on in situ measurements, and complementary methods are required to quantify the surface mass balance of unmonitored glaciers. The current study relies on the so-called albedo method, based on the analysis of albedo maps retrieved from optical satellite imagery acquired since 2000 by the MODIS sensor, on board the TERRA satellite. Recent studies revealed substantial relationships between summer minimum glacierwide surface albedo and annual surface mass balance, because this minimum surface albedo is directly related to the accumulation-area ratio and the equilibrium-line altitude. On the basis of 30 glaciers located in the French Alps where annual surface mass balance data are available, our study conducted on the period 2000-2015 confirms the robustness and reliability of the relationship between the summer minimum surface albedo and the annual surface mass balance. For the ablation season, the integrated summer surface albedo is significantly correlated with the summer surface mass balance of the six glaciers seasonally monitored. These results are promising to monitor both annual and summer glacier-wide surface mass balances of individual glaciers at a regional scale using optical satellite images. A sensitivity study on the computed cloud masks revealed a high confidence in the retrieved albedo maps, restricting the number of omission errors. Albedo retrieval artifacts have been detected for topographically incised glaciers, highlighting limitations in the shadow correction algorithm, although interannual comparisons are not affected by systematic errors.
Remote Sensing
Rock glaciers result from the long-term creeping of ice-rich permafrost along mountain slopes. Un... more Rock glaciers result from the long-term creeping of ice-rich permafrost along mountain slopes. Under warming conditions, deformation is expected to increase, and potential destabilization of those landforms may lead to hazardous phenomena. Monitoring the kinematics of rock glaciers at fine spatial resolution is required to better understand at which rate, where and how they deform. We present here the results of several years of in situ surveys carried out between 2005 and 2015 on the Laurichard rock glacier, an active rock glacier located in the French Alps. Repeated terrestrial laser-scanning (TLS) together with aerial laser-scanning (ALS) and structure-from-motion-multi-view-stereophotogrammetry (SFM-MVS) were used to accurately quantify surface displacement of the Laurichard rock glacier at interannual and pluri-annual scales. Six very high-resolution digital elevation models (DEMs, pixel size <50 cm) of the rock glacier surface were generated, and their respective quality was assessed. The relative horizontal position accuracy (XY) of the individual DEMs is in general less than 2 cm with a co-registration error on stable areas ranging from 20-50 cm. The vertical accuracy is around 20 cm. The direction and amplitude of surface displacements computed between DEMs are very consistent with independent geodetic field measurements (e.g., DGPS). Using these datasets, local patterns of the Laurichard rock glacier kinematics were quantified, pointing out specific internal (rheological) and external (bed topography) controls. The evolution of the surface velocity shows few changes on the rock glacier's snout for the first years of the observed period, followed by a major acceleration between 2012 and 2015 affecting the upper part of the tongue and the snout.
Geografiska Annaler: Series A, Physical Geography
ABSTRACT Understanding global climate change and its impacts on glaciers in the inner tropics is ... more ABSTRACT Understanding global climate change and its impacts on glaciers in the inner tropics is challenged by an absent climate seasonality that requires glacier monitoring at increased frequencies. Conejeras glacier in Colombia has been monitored monthly for 10 years, contributing to the limited knowledge of glacier mass development in this region. We acquired a terrestrial Lidar digital elevation model (DEM) and performed a full homogenization of the time series. Applying a number of interpolation methods, we calculated glacier-wide balances and deduced respective uncertainties. All interpolation methods revealed comparable variations in monthly surface mass balance, but the profile method failed in certain cases. We recommend using the Index-site method for monthly and annual and the Contour-line method for annual surface mass balances. Even when strongly reducing the stake network, the Index-site method and geostatistical interpolations (Kriging and Topo to Raster) showed robust and reliable results. Conejeras glacier is strongly down-wasting with a mass loss of 29 400 mm w.e. and an area shrinkage of 20% within 10 years. Surface mass balance variations were strongest from November to February and depend largely on the intensity of El Niño Southern Oscillation. With a repeat DEM in the near future the glaciological time series could be validated with the geodetic mass balance. We recommend continuing the monthly monitoring programme, but complementing it with an energy balance study using additional meteorological data to better explain the glacier–climate interactions. However, to track the glacier’s mass variations, a monitoring network with lower measurement frequency and stake density would be sufficient.
Journal of Glaciology, 2016
Based on an extensive dataset of surface mass balances (SMB) from four glaciers in the French Alp... more Based on an extensive dataset of surface mass balances (SMB) from four glaciers in the French Alps for the period 1995–2012 and in the framework of enhanced temperature-index models, we investigate the sensitivity of seasonal glacier SMB to temperature, solar radiation, precipitation and topographical variables. Our results reveal strong correlations between winter SMB and precipitation, although the precipitation gradient cannot explain the high-accumulation rates. Based on the available point measurements, we found no relevant relationship between winter SMB and topographical variables. Temperature was found to be the main driver of ice/snow ablation while solar radiation was found to strongly influence the spatial distribution of summer SMB. We compared the ability of several enhanced temperature-index models to accurately simulate point SMB and glacier-wide MB. Our analyses revealed that the uncertainties in the simulated annual SMB due to winter SMB uncertainties are larger tha...
Journal of Hydrology: Regional Studies
Data
Most of the world’s mountain glaciers have been retreating for more than a century in response to... more Most of the world’s mountain glaciers have been retreating for more than a century in response to climate change. Glacier retreat is evident on all continents, and the rate of retreat has accelerated during recent decades. Accurate, spatially explicit information on the position of glacier margins over time is useful for analyzing patterns of glacier retreat and measuring reductions in glacier surface area. This information is also essential for evaluating how mountain ecosystems are evolving due to climate warming and the attendant glacier retreat. Here, we present a non-comprehensive spatially explicit dataset showing multiple positions of glacier fronts since the Little Ice Age (LIA) maxima, including many data from the pre-satellite era. The dataset is based on multiple historical archival records including topographical maps; repeated photographs, paintings, and aerial or satellite images with a supplement of geochronology; and own field data. We provide ESRI shapefiles showing...
Journal of Geophysical Research: Earth Surface
Glacier mass balance (MB) data are crucial to understanding and quantifying the regional effects ... more Glacier mass balance (MB) data are crucial to understanding and quantifying the regional effects of climate on glaciers and the high-mountain water cycle, yet observations cover only a small fraction of glaciers in the world. We present a dataset of annual glacier-wide mass balance of all the glaciers in the French Alps for the 1967-2015 period. This dataset has been reconstructed using deep learning (i.e. a deep artificial neural network) based on direct MB observations and remote-sensing annual estimates, meteorological reanalyses and topographical data from glacier inventories. The method's validity was assessed previously through an extensive cross-validation against a dataset of 32 glaciers, with an estimated average error (RMSE) of 0.55 m w.e. a −1 , an explained variance (r 2) of 75 % and an average bias of −0.021 m w.e. a −1. We estimate an average regional area-weighted glacier-wide MB of −0.69±0.21 (1σ) m w.e. a −1 for the 1967-2015 period with negative mass balances in the 1970s (−0.44 m w.e. a −1), moderately negative in the 1980s (−0.16 m w.e. a −1) and an increasing negative trend from the 1990s onwards, up to −1.26 m w.e. a −1 in the 2010s. Following a topographical and regional analysis, we estimate that the massifs with the highest mass losses for the 1967-2015 period are the Chablais (−0.93 m w.e. a −1), Champsaur (−0.86 m w.e. a −1), and Haute-Maurienne and Ubaye ranges (−0.84 m w.e. a −1 each), and the ones presenting the lowest mass losses are the Mont-Blanc (−0.68 m w.e. a −1), Oisans and Haute-Tarentaise ranges (−0.75 m w.e. a −1 each). This dataset-available at https://doi.org/10.5281/zenodo.3925378 (Bolibar et al., 2020a)-provides relevant and timely data for studies in the fields of glaciology, hydrology and ecology in the French Alps in need of regional or glacier-specific annual net glacier mass changes in glacierized catchments.
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Papers by Antoine Rabatel