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Cryospheric long-term timeseries get increasingly important. To document climate-related effects on long-term viscous creep of ice-rich mountain permafrost, we investigated timeseries (1995–2022) of geodetically-derived Rock Glacier Velocity (RGV), i.e. spatially averaged interannual velocity timeseries related to a rock glacier (RG) unit or part of it. We considered 50 RGV from 43 RGs spatially covering the entire European Alps. Eight of these RGs are destabilized. Results show that RGV are distinctly variable ranging from 0.04 to 6.23 m a$^{−1}$. Acceleration and deceleration at many RGs are highly correlated with similar behaviour over 2.5 decades for 15 timeseries. In addition to a general long-term, warming-induced trend of increasing velocities, three main phases of distinct acceleration (2000–2004, 2008–2015, 2018–2020), interrupted by deceleration or steady state conditions, were identified. The evolution is attributed to climate forcing and underlines the significance of RGV as a product of the Essential Climate Variable (ECV) permafrost. We show that RGV data are valuable as climate indicators, but such data should always be assessed critically considering changing local factors (geomorphic, thermal, hydrologic) and monitoring approaches. To extract a climate signal, larger RGV ensembles should be analysed. Criteria for selecting new RGV-sites are proposed.

The European Alps cover an area of 190,900 km2, are arcuated in the western part, extend over a length of 1200 km, are up to 280 km wide, and reach their highest elevation at Mont Blanc (4807.8 m a.s.l.). Some 19% of the area exceed 2000 m. Up to 52% consist of carbonate rocks at the surface, which is relevant for karstification processes. During the Last Glacial Maximum, 55% of the Alps were covered by glaciers whereas the remaining area was impacted by moderate to severe periglacial conditions causing the formation of remarkable periglacial landforms still visible today particularly at the Alpine margin. During the Late Glacial period, previously glaciated areas were reshaped by periglacial processes forming for instance rock glaciers and solifluction landforms characterising many high-elevated regions in the Alps at present. Nowadays, active periglacial processes are restricted to elevations above 2000 m, at the central Alps to above 2400 m. Around 11% of the Alps are in this active periglacial belt, constrained by the potential treeline as the lower limit and the currently glaciated areas (1% of the Alps) as the upper limit. The widespread existence of relict and active periglacial landforms in the Alps inspired research of many scholars and scientists since centuries. Even Leonardo da Vinci made some periglacial-related observations in the late fifteenth century. Despite long traditions and comprehensive experiences in periglacial landform research, future periglacial research is still needed and will help to better understand the impact of ongoing climate change on the periglacial reshaping of this remarkable mountain chain.

Due to continental climate conditions, high elevation and high weathering rates, the Engadine is one of the rockglacier hotspots in the world and the home of research on rockglaciers.

Monitoring of the periglacial environment is relevant for many disciplines including glaciology, natural hazard management, geomorphology, and geodesy. Since October 2022, Rock Glacier Velocity (RGV) is a new Essential Climate Variable (ECV) product within the Global Climate Observing System (GCOS). However, geodetic surveys at high elevation remain very challenging due to environmental and logistical reasons. During the past decades, the introduction of low-cost global navigation satellite system (GNSS) technologies has allowed us to increase the accuracy and frequency of the observations. Today, permanent GNSS instruments enable continuous surface displacement observations at millimetre accuracy with a sub-daily resolution. In this paper, we describe decennial time series of GNSS observables as well as accompanying meteorological data. The observations comprise 54 positions located on different periglacial landforms (rock glaciers, landslides, and steep rock walls) at altitudes ranging from 2304 to 4003 ma.s.l. and spread across the Swiss Alps. The primary data products consist of raw GNSS observables in RINEX format, inclinometers, and weather station data. Additionally, cleaned and aggregated time series of the primary data products are provided, including daily GNSS positions derived through two independent processing tool chains. The observations documented here extend beyond the dataset presented in the paper and are currently continued with the intention of long-term monitoring. An annual update of the dataset, available at https://doi.org/10.1594/PANGAEA.948334 (Beutel et al., 2022),​​​​​​​ is planned. With its future continuation, the dataset holds potential for advancing fundamental process understanding and for the development of applied methods in support of e.g. natural hazard management.

Digitized aerial images were used to monitor the evolution of perennially frozen debris and polythermal glacier ice at the intensely investigated Gruben site in the Swiss Alps over a period of about 50 years. The photogrammetric analysis allowed for a compilation of detailed spatio-temporal information on flow velocities and thickness changes. In addition, high-resolution GNSS (global navigation satellite system) and ground surface temperature measurements were included in the analysis to provide insight into short-term changes. Over time, extremely contrasting developments and landform responses are documented. Viscous flow within the warming and already near-temperate rock glacier permafrost continued at a constant average but seasonally variable speed of typically decimetres per year, with average surface lowering limited to centimetres to a few decimetres per year. This constant flow causes the continued advance of the characteristic convex, lava-stream-like rock glacier with its oversteepened fronts. Thawing rates of ice-rich perennially frozen ground to strong climate forcing are very low (centimetres per year) and the dynamic response strongly delayed (timescale of decades to centuries). The adjacent cold debris-covered glacier tongue remained an essentially concave landform with diffuse margins, predominantly chaotic surface structure, intermediate thickness losses (decimetres per year), and clear signs of down-wasting and decreasing flow velocity. The former contact zone between the cold glacier margin and the upper part of the rock glacier with disappearing remains of buried glacier ice embedded on top of frozen debris exhibits complex phenomena of thermokarst in massive ice and backflow towards the topographic depression produced by the retreating glacier tongue. As is typical for glaciers in the Alps, the largely debris-free glacier part shows a rapid response (timescale of years) to strong climatic forcing with spectacular retreat (>10 m a−1) and mass l

The creation and curation of environmental data present numerous challenges and rewards. In this study, we reflect on the increasing amount of freely available glacier data (inventories and changes), as well as on related demands by data providers, data users, and data repositories in-between. The amount of glacier data has increased significantly over the last two decades as remote sensing techniques have improved and free data access is much more common. The portfolio of observed parameters has increased as well, which presents new challenges for international data centers, and fosters new expectations from users. We focus here on the service of the Global Terrestrial Network for Glaciers (GTN-G) as the central organization for standardized data on glacier distribution and change. Within GTN-G, different glacier datasets are consolidated under one umbrella, and the glaciological community supports this service by actively contributing their datasets and by providing strategic guidance via an Advisory Board. To assess each GTN-G dataset, we present a maturity matrix and summarize achievements, challenges, and ambitions. The challenges and ambitions in the democratization of glacier data are discussed in more detail, as they are key to providing an even better service for glacier data in the future. Most challenges can only be overcome in a financially secure setting for data services and with the help of international standardization as, for example, provided by the CoreTrustSeal. Therefore, dedicated financial support for and organizational long-term commitment to certified data repositories build the basis for the successful democratization of data. In the field of glacier data, this balancing act has so far been successfully achieved through joint collaboration between data repository institutions, data providers, and data users. However, we also note an unequal allotment of funds for data creation and projects using the data, and data curation. Considering the

Many contemporary high-latitude and high-altitude regions are covered by ice and snow perennially or at least for substantial parts of the year, and such coverage extended greatly during colder periods of the Quaternary. Consequently, the landscape of such regions typically bears the strong imprint of ice- and snow-related processes operating over Quaternary-to-modern timescales. There has been strong research interest in the nature, rate, and efficacy of cold-region geomorphic processes, though most research has been devoted to glacial and permafrost phenomena, with comparably few studies having quantitatively addressed the role of snow as a land-forming agent. Here we review current research on land-forming processes related to glacial erosion and deposition, permafrost and periglacial processes, and snow-related processes such as nivation, snow creep, and snow avalanching. Our objective is to highlight those questions that drive current research and indicate others that seem sufficiently worthy to further our understanding of geomorphic form and process in the cryosphere. We do so bearing in mind that such knowledge is essential for successfully predicting form and process, and hence avoiding snow- and ice-related hazards. We conclude by outlining a number of recommendations for future research in the field.

The Engadine is one of the rockglacier hot spots in the European Alps. Many rockglaciers in all states of activity (active, inactive, relict) are found, indicating the former and present occurrence of permafrost. This is due to continental climate conditions, high elevation, and high weathering rates. Rockglaciers are developed in valley bottoms, such as the Val Sassa and the Val da l’Acqua rockglacier, or in formerly glaciated cirques, such as the Muragl or the Murtèl rockglacier. Hence, the Engadine is the home of research on rockglaciers in Europe with the first studies on rockglaciers of the Swiss National Park one century ago. Engadine was also the first place in the world where boreholes in rockglaciers were drilled in 1987. Nowadays, several Engadine rockglaciers are monitored within the Permafrost Monitoring Network Switzerland (PERMOS).

Although worldwide inventories of glacier area have been coordinated internationally for several decades, a similar effort for glacier ice thicknesses was only initiated in 2013. Here, we present the third version of the Glacier Thickness Database (GlaThiDa v3), which includes 3 854 279 thickness measurements distributed over roughly 3000 glaciers worldwide. Overall, 14 % of global glacier area is now within 1 km of a thickness measurement (located on the same glacier) – a significant improvement over GlaThiDa v2, which covered only 6 % of global glacier area and only 1100 glaciers. Improvements in measurement coverage increase the robustness of numerical interpolations and model extrapolations, resulting in better estimates of regional to global glacier volumes and their potential contributions to sea-level rise.In this paper, we summarize the sources and compilation of glacier thickness data and the spatial and temporal coverage of the resulting database. In addition, we detail our use of open-source metadata formats and software tools to describe the data, validate the data format and content against this metadata description, and track changes to the data following modern data management best practices. Archived versions of GlaThiDa are available from the World Glacier Monitoring Service (e.g., v3.1.0, from which this paper was generated: https://doi.org/10.5904/wgms-glathida-2020-10; GlaThiDa Consortium, 2020), while the development version is available on GitLab (https://gitlab.com/wgms/glathida, last access: 9 November 2020).

The ongoing acceleration in rock glacier velocities concurrent with increasing air temperatures, and the widespread onset of rock glacier destabilization have reinforced the interest in rock glacier dynamics and in its coupling to the climate system. Despite the increasing number of studies investigating this phenomenon, our knowledge of both the fundamental mechanisms controlling rock glacier dynamics, and their long‐term behaviour at the regional scale remain limited. We present a general theory to investigate rock glacier dynamics, its spatial patterns and temporal trends at both regional and local scale. To this end, we combine a model to calculate rock glacier thickness with an empirical creep model for ice‐rich debris, in order to derive the Bulk Creep Factor (BCF), which allows to disentangle the two contributions to the surface velocities from (i) material properties and (ii) geometry. Thereafter, we provide two examples of possible applications of this approach at a regional and local scale.

Seit dem Ende der sogenannten «Kleinen Eiszeit» um 1850 ziehen sich die Gletscher zurück und hinterlassen eindrückliche Landschaften. Diese sind gezeichnet von grossen Moränenbastionen, vereinzelten Seen, Mengen an lockerem Sediment, aufkommender Vegetation und wilden Bachläufen. Solche Landschaften zeigen sich in den meisten vergletscherten Regionen der Erde, so auch in den Europäischen Alpen. In den letzten 20 Jahren hat sich der Gletscherschwund nochmals deutlich verstärkt. Etwa 17 Prozent des gesamten Eisvolumens der Alpen sind seit der Jahrtausendwende verschwunden, das entspricht etwa 22 Kubikkilometern (Sommer et al. 2020). Die stärksten Verluste traten in den Gebirgsmassiven der Schweizer Alpen auf, wie zum Beispiel in der Region Jungfrau-Aletsch. Hier ging die Eisdicke zwischen 2000 und 2014 im Durchschnitt um 0.72 Meter pro Jahr zurück. Der starke Gletscherrückgang hinterlässt in den Vorfeldern der Gletscher deutliche Spuren und das zurückweichende Eis macht Platz für andere Transportmedien, wie das Wasser und die Gravitation.

Comprehensive assessments of global glacier mass changes based on a variety of observations and prevailing methodologies have been published at multi-annual intervals. For the years in between, the glaciological method provides annual observations of specific mass changes but is suspected to not be representative at the regional to global scales due to uneven glacier distribution with respect to the full sample. Here, we present a simple approach to estimate and correct for this bias in the glaciological sample and, hence, to provide an ad hoc estimate of global glacier mass changes and corresponding sea-level equivalents for the latest years, i.e. about −300±250 Gt in 2016/17 and −500±200 Gt in 2017/18.

Although worldwide inventories of glacier area have been coordinated internationally for several decades, a similar effort for glacier ice thicknesses was only initiated in 2013. Here, we present the third version of the Glacier Thickness Database (GlaThiDa v3), which includes 3 854 279 thickness measurements distributed over roughly 3000 glaciers worldwide. Overall, 14 % of global glacier area is now within 1 km of a thickness measurement (located on the same glacier) – a significant improvement over GlaThiDa v2, which covered only 6 % of global glacier area and only 1100 glaciers. Improvements in measurement coverage increase the robustness of numerical interpolations and model extrapolations, resulting in better estimates of regional to global glacier volumes and their potential contributions to sea-level rise. In this paper, we summarize the sources and compilation of glacier thickness data and the spatial and temporal coverage of the resulting database. In addition, we detail our use of open-source metadata formats and software tools to describe the data, validate the data format and content against this metadata description, and track changes to the data following modern data management best practices. Archived versions of GlaThiDa are available from the World Glacier Monitoring Service (e.g., v3.1.0, from which this paper was generated: https://doi.org/10.5904/wgms-glathida-2020-10; GlaThiDa Consortium, 2020), while the development version is available on GitLab (https://gitlab.com/wgms/glathida, last access: 9 November 2020).

Comprehensive assessments of global glaciermass changes based on a variety of observations and prevailing methodologies have been published at multi-annual intervals. For the years in between, the glaciological method provides annual observations of specific mass changes but is suspected to not be representative at the regional to global scales due to uneven glacier distribution with respect to the full sample. Here, we present a simple approach to estimate and correct for this bias in the glaciological sample and, hence,to provide an ad hoc estimate of global glacier mass changes and corresponding sea-level equivalents for the latest years, i.e. about −300±250 Gt in 2016/17 and −500±200 Gt in 2017/18.

In mid-latitude mountains, most of the valley glaciers currently experience distinct and enhanced volume and area loss. In parallel with the glacier retreat, the related proglacial areas enlarge, leaving unconsolidated sediments and ground ice of different origins and thus forming a transitional landscape, as developing from a glacial to a non-glacial environment. The erosion, transport and accumulation of sediment in these proglacial areas are characterized by high spatio-temporal dynamics, which are typically highest in the direct glacier forefield and become more inactive with increasing distance to the glacier front. Glacial, periglacial, fluvial and gravitational processes occur and highly interact in space and time. The glacial history of recently deglaciated zones influences the complex thermal regime of the subsurface and determines the current ground ice occurrence. Besides the glacio-fluvial processes, low-temperature conditions, as well as the occurrence of ground ice, are the most effective drivers for geomorphic dynamics and related landform evolution in these proglacial areas. A deeper knowledge of ongoing processes as well as of the amounts of sediment and ground ice is decisive to assess the availability of unconsolidated sediment for potential hazardous processes (e.g. debris flows) and the availability of water from ground ice bodies. There is an increasing need for high-resolution data (e.g. repeated topographic data) of proglacial areas as well as the systematic monitoring of these environments. Keywords Ground ice Dead ice Permafrost Rockglaciers Geophysical measurements

It is widely accepted that glaciers are retreating throughout the world and that their decline causes serious impacts on many societies. Knowledge of glacier distribution and quantification of glacier changes is crucial to assessing the impact of glacier shrinkage on the transboundary hydrological cycle and related issues, such as irrigation, energy production, and natural hazard prevention. Therefore, glacier monitoring is vital to the development of sustainable adaptation strategies in regions with glaciated mountains. Baseline documentation is needed to assess the current status of glacier monitoring. The aim of this study is to assess the status of national implementations of the international monitoring strategy developed by the Global Terrestrial Network for Glaciers (GTN-G) to make the data easily accessible to a broader audience, to identify gaps in the monitoring setup, and to guide countries in improving their monitoring schemes. We developed a standardized procedure to evaluate existing glacier data from international data repositories; these freely accessible data on glacier distribution and changes (as of 2015) for all glacierized countries and regions form the basis of this study. The resulting country profiles are analyzed in relation to the existing GTN-G monitoring strategy. Gaps between the current implementation of glacier monitoring and implementation targets are compiled in a solid gap analysis, which allows countries to be categorized as having poorly developed monitoring, needing improvement, or having well-developed monitoring. Three pilot cases (Kyrgyzstan, Bolivia, and Switzerland) are presented in detailed country profiles.

In recent years, observations have highlighted seasonal and interannual variability in rock glacier flow. Temperature forcing, through heat conduction, has been proposed as one of the key processes to explain these variations in kinematics. However, this mechanism has not yet been quantitatively assessed against real-world data. We present a 1-D numerical modelling approach that couples heat conduction to an empirically derived creep model for ice-rich frozen soils. We use this model to investigate the effect of thermal heat conduction on seasonal and interannual variability in rock glacier flow velocity. We compare the model results with borehole temperature data and surface velocity measurements from the PERMOS and PermaSense monitoring network available for the Swiss Alps. We further conduct a model sensitivity analysis in order to resolve the importance of the different model parameters. Using the prescribed empirically derived rheology and observed near-surface temperatures, we are able to model the correct order of magnitude of creep. However, both interannual and seasonal variability are underestimated by an order of magnitude, implying that heat conduction alone cannot explain the observed variations. Therefore, we conclude that non-conductive processes, likely linked to water availability, must dominate the short-term velocity signal.

Während die Erforschung der Vergletscherung der Alpen und anderer Gebirge auf eine mehr als 150jährige Geschichte zurückblickt, rückte der Permafrost als verborgene Vereisung im Innern von Böden, Schuttmassen und Felsen der Gebirge erst seit den ausgehenden 1970er-Jahren verstärkt in den Fokus und wurde Wissenschaftlich dokumentiert. Für die Veränderungen von Permafrost im Hochgebirge gibt es bis auf wenige Ausnahmen erst seit den 1980er-Jahren verlässliche Messreihen, was die Analyse der Auswirkungen des Klimawandels heute erheblich erschwert. Nach Einschätzungen mehrerer Studien gehören die Permafrostveränderungen im Zuge des Klimawandels in den Hochgebirgen aktuell zu den wichtigsten Einfl ussfaktoren für alpine Naturgefahren.

Permafrost is a thermal phenomenon of the lithosphere and applies to ground that remains at or below 0°C for at least two consecutive years. Permafrost is coupled to atmospheric conditions and as such is sensitive to climatic changes. Thawing of permafrost can lead to destabilization of steep slopes or infrastructure, and a major concern is the release of radiative active forcing gases such as methane stored in permafrost ground. Projections of permafrost changes suggest further degradation in both high altitudes and high latitudes.

Permafrost is a thermal phenomenon of the lithosphere and applies to ground that remains at or below 0°C for at least two consecutive years. Permafrost is coupled to atmospheric conditions and as such is sensitive to climatic changes. Thawing of permafrost can lead to destabilization of steep slopes or infrastructure, and a major concern is the release of radiative active forcing gases such as methane stored in permafrost ground. Projections of permafrost changes suggest further degradation in both high altitudes and high latitudes.

The word rockglacier is not in any dictionary and is rarely used in the literature. The proper spelling is as two words, which we therefore prefer. Rock glaciers are landforms that form as a result of creeping mountain permafrost which have received considerable attention concerning their dynamical and thermal changes. Observed changes in rock glacier motion on seasonal to decadal timescales have been linked to ground temperature variations and related changes in landform geometries interpreted as signs of degradation due to climate warming. Despite the extensive kinematic and thermal monitoring of these creeping permafrost landforms, our understanding of the controlling factors remains limited and lacks robust quantitative models of rock glacier evolution in relation to their environmental setting. Here, we use a holistic approach to analyze the current and long-term dynamical development of two rock glaciers in the Swiss Alps. Site-specific sedimentation and ice generation rates are linked with an adapted numerical flow model for rock glaciers that couples the process chain from material deposition to rock glacier flow in order to reproduce observed rock glacier geometries and their general dynamics. Modeling experiments exploring the impact of variations in rock glacier temperature and sediment–ice supply show that these forcing processes are not sufficient to explain the currently observed short-term geometrical changes derived from multitemporal digital terrain models at the two different rock glaciers. The modeling also shows that rock glacier thickness is dominantly controlled by slope and rheology while the advance rates are mostly constrained by rates of sediment–ice supply. Furthermore, timescales of dynamical adjustment are found to be strongly linked to creep velocity. Overall, we provide a useful modeling framework for a better understanding of the dynamical response and morphological changes of rock glaciers to changes in external forcing.

One of the grand challenges in glacier research is to assess the total ice volume and its global distribution. Over the past few decades the compilation of a world glacier inventory has been well-advanced both in institutional set-up and in spatial coverage. The inventory is restricted to glacier surface observations. However, although thickness has been observed on many glaciers and ice caps around the globe, it has not yet been published in the shape of a readily available database. Here, we present a standardized database of glacier thickness observations compiled by an extensive literature review and from airborne data extracted from NASA's Operation IceBridge. This database contains ice thickness observations from roughly 1100 glaciers and ice caps including 550 glacier-wide estimates and 750,000 point observations. A comparison of these observational ice thicknesses with results from area- and slope- dependent approaches reveals large deviations both from the observations and between different estimation approaches. For glaciers and ice caps all estimation approaches show a tendency to overestimation. For glaciers the median relative absolute deviation lies around 30% when analyzing the different estimation approaches. This initial database of glacier and ice caps thickness will hopefully be further enlarged and intensively used for a better understanding of the global glacier ice volume and its distribution.

Observations show that glaciers around the world are in retreat and losing mass. Internationally coordinated for over a century, glacier monitoring activities provide an unprecedented dataset of glacier observations from ground, air and space. Glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass-balance data relating to the impact that glaciers exercise on global sea-level fluctuations or on regional runoff. In this study we provide an overview and analysis of the main observational datasets compiled by the World Glacier Monitoring Service (WGMS). The dataset on glacier front variations (⇠42 000 since 1600) delivers clear evidence that centennial glacier retreat is a global phenomenon. Intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the Little Ice Age (or Holocene). Glaciological and geodetic observations (⇠5200 since 1850) show that the rates of early 21st-century mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history, as indicated also in reconstructions from written and illustrated documents. This strong imbalance implies that glaciers in many regions will very likely suffer further ice loss, even if climate remains stable.

This book focuses on the complexities of glaciers as documented via satellite observations. The complexities drive much scientific interest in the subject. The essence—that the world’s glaciers and ice caps exhibit overwhelming retreat—is also developed by this book. In this introductory chapter, we aim at providing the reader with background information to better understand the integration of the glacier-mapping initiative known as Global Land Ice Measurements from Space (GLIMS, http://www.glims.org ) within the framework of internationally coordinated glacier-monitoring activities. The chapter begins with general definitions of perennial ice on land and its global coverage, followed by a section on the relation between glaciers and climate. Brief overviews on the specific history of internationally coordinated glacier monitoring and the global monitoring strategy for glaciers and ice caps are followed by a summary of available data. We introduce the potential and challenges of satellite remote sensing for glacier monitoring in the 21st century and emphasize the importance of integrative change assessments. Lastly, we provide a synopsis of the book structure as well as some concluding remarks on worldwide glacier monitoring.

One of the grand challenges in glacier research is to assess the total ice volume and its global distribution. Over the past few decades the compilation of a world glacier inventory has been well-advanced both in institutional set-up and in spatial coverage. The inventory is restricted to glacier surface observations. However, although thickness has been observed on many glaciers and ice caps around the globe, it has not yet been published in the shape of a readily available database. Here, we present a standardized database of glacier thickness observations compiled by an extensive literature review and from airborne data extracted from NASA's Operation IceBridge. This database contains ice thickness observations from roughly 1100 glaciers and ice caps including 550 glacier-wide estimates and 750,000 point observations. A comparison of these observational ice thicknesses with results from area- and slope-dependent approaches reveals large deviations both from the observations and between different estimation approaches. For glaciers and ice caps all estimation approaches show a tendency to overestimation. For glaciers the median relative absolute deviation lies around 30% when analyzing the different estimation approaches. This initial database of glacier and ice caps thickness will hopefully be further enlarged and intensively used for a better understanding of the global glacier ice volume and its distribution.

The ongoing acceleration in rock glacier velocities concurrent with increasing air temperatures, and the widespread onset of rock glacier destabilization have reinforced the interest in rock glacier dynamics and in its coupling to the climate system. Despite the increasing number of studies investigating this phenomenon, our knowledge of both the fundamental mechanisms controlling rock glacier dynamics, and their long‐term behaviour at the regional scale remain limited. We present a general theory to investigate rock glacier dynamics, its spatial patterns and temporal trends at both regional and local scale. To this end, we combine a model to calculate rock glacier thickness with an empirical creep model for ice‐rich debris, in order to derive the Bulk Creep Factor (BCF), which allows to disentangle the two contributions to the surface velocities from (i) material properties and (ii) geometry. Thereafter, we provide two examples of possible applications of this approach at a regional and local scale.

Although worldwide inventories of glacier area have been coordinated internationally for several decades, a similar effort for glacier ice thicknesses was only initiated in 2013. Here, we present the third version of the Glacier Thickness Database (GlaThiDa v3), which includes 3 854 279 thickness measurements distributed over roughly 3000 glaciers worldwide. Overall, 14 % of global glacier area is now within 1 km of a thickness measurement (located on the same glacier) – a significant improvement over GlaThiDa v2, which covered only 6 % of global glacier area and only 1100 glaciers. Improvements in measurement coverage increase the robustness of numerical interpolations and model extrapolations, resulting in better estimates of regional to global glacier volumes and their potential contributions to sea-level rise.In this paper, we summarize the sources and compilation of glacier thickness data and the spatial and temporal coverage of the resulting database. In addition, we detail our use of open-source metadata formats and software tools to describe the data, validate the data format and content against this metadata description, and track changes to the data following modern data management best practices. Archived versions of GlaThiDa are available from the World Glacier Monitoring Service (e.g., v3.1.0, from which this paper was generated: https://doi.org/10.5904/wgms-glathida-2020-10; GlaThiDa Consortium, 2020), while the development version is available on GitLab (https://gitlab.com/wgms/glathida, last access: 9 November 2020).

Comprehensive assessments of global glacier mass changes based on a variety of observations and prevailing methodologies have been published at multi-annual intervals. For the years in between, the glaciological method provides annual observations of specific mass changes but is suspected to not be representative at the regional to global scales due to uneven glacier distribution with respect to the full sample. Here, we present a simple approach to estimate and correct for this bias in the glaciological sample and, hence, to provide an ad hoc estimate of global glacier mass changes and corresponding sea-level equivalents for the latest years, i.e. about −300±250 Gt in 2016/17 and −500±200 Gt in 2017/18.

One of the grand challenges in glacier research is to assess the total ice volume and its global distribution. Over the past few decades the compilation of a world glacier inventory has been well-advanced both in institutional set-up and in spatial coverage. The inventory is restricted to glacier surface observations. However, although thickness has been observed on many glaciers and ice caps around the globe, it has not yet been published in the shape of a readily available database. Here, we present a standardized database of glacier thickness observations compiled by an extensive literature review and from airborne data extracted from NASA's Operation IceBridge. This database contains ice thickness observations from roughly 1100 glaciers and ice caps including 550 glacier-wide estimates and 750,000 point observations. A comparison of these observational ice thicknesses with results from area- and slope- dependent approaches reveals large deviations both from the observations and between different estimation approaches. For glaciers and ice caps all estimation approaches show a tendency to overestimation. For glaciers the median relative absolute deviation lies around 30% when analyzing the different estimation approaches. This initial database of glacier and ice caps thickness will hopefully be further enlarged and intensively used for a better understanding of the global glacier ice volume and its distribution.