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The article published by Obu et al. (2019) estimating the occurrence of permafrost over a Northern Hemisphere. The results published differ from those presented in previous works. This comment highlights the errors introduced in that study, and in a positive note, its cause and proposed solution. The problem remains beyond capabilities of computed models or empirical research. Its solution lies in using the correct categories and land classifications, and clearly defining the medium subjected to freezing. In particular, the correct classification of ice plays a decisive role here. To provide a full picture of the occurrence of permafrost on the Earth surface, three different media must be considered: 1) exposed land, traditionally understood as "dry land", 2) glaciers and ice sheets together with its bed and 3) the sea floor (continental shelves). The biggest weakness of the published study is not including glaciated areas in their estimations. The authors do not take either a clear position in this crucial matter, despite a radical divergence of opinions has emerged in recent years. Whether and in what way Greenland or other glaciated areas are covered by permafrost remains a pressing issue, as the final determination of the range of the permafrost worldwide depends on it. Until then, any criteria or benchmark used will continue to be ambiguous and open to discussion, maintaining the discrepancy at millions of square kilometers. [ABSTRACT FROM AUTHOR]

The Northeast Greenland Ice Stream (NEGIS) is the main artery for ice discharge from the northeast sector of the Greenland Ice Sheet (GrIS) to the North Atlantic. Understanding the past, present and future stability of the NEGIS with respect to atmospheric and oceanic forcing is of global importance as it drains around 17% of the GrIS and has a sea-level equivalent of 1.6 m. This paper reconstructs the deglacial and Holocene history of Nioghalvfjerdsbræ (or 79N Glacier); a major outlet of the NEGIS. At high elevation (>900 m asl) autochthonous blockfield, a lack of glacially moulded bedrock and pre LGM exposure ages point to a complex exposure/burial history extending back over half a million years. However, post Marine Isotope Stage 12, enhanced glacial erosion led to fjord incision and plateaux abandonment. Between 900 and 600 m asl the terrain is largely unmodified by glacial scour but post LGM erratics indicate the advection of cold-based ice through the fjord. In contrast, below ∼600 m asl Nioghalvfjerdsfjorden exhibits a geomorphological signal indicative of a warm-based ice stream operating during the last glacial cycle. Dated ice marginal landforms and terrain along the fjord walls show initial thinning rates were slow between ∼23 and 10 ka, but post-10 ka it is evident that Nioghalvfjerdsfjorden deglaciated extremely quickly with complete fjord deglaciation below ∼500 m asl between 10.0 and 8.5 ka. Both increasing air and ocean temperatures were pivotal in driving surface lowering and submarine melt during deglaciation, but the final withdrawal of ice through Nioghalvfjerdsfjorden was facilitated by the action of marine ice sheet instability. Our estimates show that thinning and retreat rates reached a maximum of 5.29 ma−1 and 613 ma−1, respectively, as the ice margin withdrew westwards. This would place the Early Holocene disintegration of this outlet of the NEGIS at the upper bounds of contemporary thinning and retreat rates seen both in Greenland and Antarctica. Combined with recent evidence of ice stream shutdown during the Holocene, as well as predictions of changing ice flow dynamics within downstream sections of the NEGIS catchment, this suggests that significant re-organisation of the terminal zone of the ice stream is imminent over the next century. • The Northeast Greenland Ice Stream (NEGIS) thinned slowly between 23–10ka as ice retreated across the continental shelf. • At the opening of the Holocene rising air & ocean temperatures drove surface lowering & basal melt. • Between 10-8.5ka marine ice sheet instability further enhanced grounding line retreat rates into Nioghalvfjerdsfjorden. • During the Early Holocene thinning and retreat rates reached a maximum of 5.29 ma-1 and 613 ma-1 respectively. • Such rates are at the upper bounds of contemporary ice stream thinning and retreat rates in Greenland and Antarctica. [ABSTRACT FROM AUTHOR]

The collapse of glacial, permafrost, and ice-rich moraine slopes in high-altitude mountainous areas not only threatens downstream residents and infrastructure but also displaces ice mass to lower and warmer elevations, accelerating glacial ablation to some extent. Despite being considered rare, ice-rich slopes collapse more frequently than commonly thought due to climate change. For example, two adjacent mountain glaciers in the Aru Range of the Tibetan Plateau, characterized by large volumes (68 × 106 m3 and 83 × 106 m3, respectively) and low surface slope angles (12.3° and 12.9°, respectively), collapsed surprisingly in 2016. While the mechanisms behind these collapses have garnered broad attention, the ability to quantitatively assess the instability of ice-rich slopes remains limited due to the complex interplay of multi-physical processes. Taking the Aru glacier collapses as reference cases, this paper presents a conceptual model, implemented through coupled thermo-hydro-mechanical simulation, to evaluate the stability of high-altitude ice-rich slopes due to climate change, rainfall and ice ablation. Results indicate that the methodology captures the effects of temperature change, rainfall and meltwater on the instability events well, demonstrating promising potential in evaluating potential collapse zones of ice-rich slopes similar to the Aru glaciers. Furthermore, the role of climate change in the well-known Aru events is demonstrated using a state-of-the-art global climate reanalysis dataset. Findings reveal that the increase in liquid water infiltrating the Aru glaciers since 2010 was a critical factor leading to the instability events. • A conceptual model is proposed to analyse the stability and collapse zones of ice-rich slopes. • The modelling elucidates the causes of twin collapses of the Aru glaciers. • Results contribute to ice-rich slope instability prediction and associated disaster risk management. [ABSTRACT FROM AUTHOR]

Mountain glaciers are one of the most sensitive indicators of climate change. Reconstructing past glacier extents provides valuable insights into the climate change for specific regions where instrumental records are not enough and even absent. In the paper we mapped the outlines for 691 Little Ice Age (LIA) glaciers in terms of prominent moraines beyond contemporary glaciers in the Tanggula Mountains, central Tibetan Plateau (TP). Based on these glacier outlines, we reconstructed the ice thicknesses and surfaces for the LIA glaciers in the region. Accordingly, we calculated the equilibrium-line altitudes (ELAs) for contemporary and LIA glaciers. By comparing the ELAs between the contemporary and LIA glaciers, we estimated the LIA summer temperature decreases in different subregions of the Tanggula Mountains. Since the LIA, the ELA have risen by 35.6 ± 18.8 m, 26.1 ± 17.6 m, and 63.1 ± 38.6 m in the respective western, central, and eastern subregions of the Tanggula Mountains. Assuming no change in precipitation, the LIA summer temperature would decrease by 0.22 ± 0.12 °C, 0.14 ± 0.09 °C, and 0.34 ± 0.21 °C in the three subregions, respectively. Moreover, glaciers in the western, central, and eastern subregions have lost 13.3%, 23.9%, and 42.8% of their area, 15.4%, 25.3%, and 39.6% of their length, and 20.8%, 39.0%, and 61.0% of their volume, respectively. By compiling the LIA ELA data from previous studies, we also estimated the LIA summer temperature changes for other regions of the TP. The LIA ELA and summer temperature changes relative to the present showed a decreasing trend from the edges towards the interior on the TP. • LIA glaciers and summer climate were reconstructed at the Tanggula Mountains. • LIA summers were 0.22 ± 0.12 °C, 0.14 ± 0.09 °C, and 0.34 ± 0.21 °C cooler than present in three subregions. • Summer temperature change had a decreasing trend from the edges towards the interior on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

• Groundwater recharge changes with freeze–thaw processes. • The complete thawing period contributed the highest recharge amount at the fastest recharge speed. • Groundwater recharge during the freezing period is strongly influenced by temperature. Accurate estimation of groundwater recharge (GR) is crucial for sustainable groundwater use, particularly in alpine regions that are sensitive to climate change response. However, quantifying the amount of GR in these areas is challenging due to the absence of measurement data and an unclear understanding of the GR mechanism. In this paper, we proposed a new method (HS-IWTF) for estimating GR in the central Qinghai-Tibet Plateau. The method utilized Hydrus-1D to create an unsaturated zone soil water transport model, which provides a reference value for specific yield (Sy). Additionally, the method incorporated the impact of groundwater potential decline at various freeze–thaw stages to improve recharge estimation. The results showed that HS-IWTF method can be better applied for estimating GR in alpine regions. The simulated recharge of groundwater though vertical infiltration ranged from 191.7 to 217.8 mm/yr, primarily from precipitation infiltration. The total GR ranged from 312.1 to 405.0 mm/yr, with significant recharge contributed by snow and ice thaw and lateral runoff. The HS-IWTF method is more precise and reliable than simulated infiltration and traditional water table fluctuation (WTF) method in reflecting recharge changes at various monitoring sites during each freeze–thaw period. The thawing process period (0.95 mm/d, 11 %) and the complete thawing period (1.07 mm/d, 61 %) contributed more recharge at higher recharge rates due to improved recharge sources and conditions. The air temperature rise promoted the degradation of the cryosphere and raised the ratio of recharge precipitation (GR/PT), particularly in regions with high altitude and proximity to permafrost and glaciers where recharge was significantly high during the freezing period. This study provides valuable information on the measurement of GR in alpine regions and the crucial role of freeze–thaw processes in GR. [ABSTRACT FROM AUTHOR]

This paper argues that the Rocky Mountains played a significantly more important role in the process of the peopling of the New World than archaeologists have traditionally recognized. Although First Americans did not reach the Rockies before they set foot in any other New World region—they could not have, regardless of their point of entry—by Clovis time, evidence suggests that Clovis people knew the Rocky Mountain landscape intimately. Archaeologists should have long anticipated this, given the many resources the Rocky Mountains offer that adjacent, albeit archaeologically better-known regions such as the Plains and some parts of the Far West do not; at least not as ubiquitously. These include plentiful water in the form of streams, lakes, snowpack, and glaciers; high-quality sources of obsidian, chert, quartzite and other knappable stone; and a vertically oriented landscape that maximizes floral and faunal diversity within comparatively condensed space. Two other non-economic characteristics likely contributed significantly to the appeal of the Rocky Mountains to some First Americans: the power and sanctity nearly all humans attribute to mountains, and the seemingly little-recognized fact that northeast Asian Upper Paleolithic people who populated the New World during the terminal Pleistocene occupied mountainous landscapes for some 45,000 years prior to their departure. For many First Americans, mountains—not the flat, windswept tundra of Siberian stereotypes—had always been home. Evidence for the familiarity of Clovis groups with the Rocky Mountain landscapes comes principally from three Clovis caches: Anzick, Fenn, and Mahaffy. All three caches are located in the Rockies, collectively contain artifacts made from ten of the highest-quality stone raw materials available in the Southern, Central and Northern Rockies, and at least one of the caches accompanies the burial of a young child who appears to have been interred intentionally on a prominent and likely sacred landform in a mountain valley. Bringing the paper's argument full circle, that same child's genetic profile shows a direct link to that of another youngster buried thousands of years earlier at the Late Glacial Maximum Mal'ta site in the mountainous Trans-Baikal region of Siberia. [ABSTRACT FROM AUTHOR]

This paper reviews the current state of knowledge about environmental changes at the MIS 3/2 transition in the northern Alps and their foreland, covering the time frame from 35 to 25 ka. Lake and peat deposits, cave sediments, loess and glacial deposits are presented and the response of their biotic and abiotic proxies to climate change is discussed. During late MIS 3, interstadial conditions, albeit weak, occurred at c. 36–32 ka. At climatically favourable sites, small patches of trees (mainly Pinus and some Betula) existed together with some shrubs. The environmental conditions during late MIS 3 are also reflected by a boreal brown soil horizon, a cambisol called Lohne soil, found in many loess sequences. Subsequently, the environmental conditions became harsher as shown by the proxy data. From c. 30 ka onwards the absence of pedogenesis sensu stricto and the plant assemblages point to an Arctic climate in the northern Alpine foreland. Accentuating, glaciers advanced beyond the northern limit of the Alps around the MIS 3/2 boundary and reached their maximum extent in the foreland at about 25 ka. [ABSTRACT FROM AUTHOR]

The Karakoram region contains a large number of surge-type glaciers, but few surging glaciers have been investigated by surface displacement and DEM differencing. The paper presents the surge dynamics of one unnamed glacier in Yarkand basin, of Karakoram region between 2000 and 2019 using satellite imagery (e.g., Landsat and Sentinel 2). Also, multiple high-resolution DEMs (e.g., HMA and Cartosat 1) were used to estimate mass transfer from the reservoir zone to the receiving zone. The DEM differencing exhibit maximum thickening of the lower receiving zone was ~190 ± 31 m whereas a maximum thinning of the upper reservoir zone was −17 ± 31 m between 2018 and 2016. The receiving zone gained 256 ± 143 × 106 m3 ice mass between 2018 and 2011. The surface displacement was lower than 0.07 ± 0.02 m d−1 in the quiescent phase between 2000 and 2011 and it reached to ~5 ± 0.3 m d−1 in the active phase (autumn 2015). The glacier terminus retreated −765 ± 89 m from 1978 to 2016 but advanced +681 ± 57 m during 2016–2019. This analysis indicate that the gradual increase in surface displacement about four years before the onset of the surge, long active phase (three years) and slow termination corroborate partially thermally controlled Svalbard-type surge. [ABSTRACT FROM AUTHOR]

With the availability of improved digital elevation models (DEMs) of global coverage, the morphological analysis of large populations of glacial cirques is possible, and can be used to derive important palaeoclimate and environmental information related to the distribution and history of former glaciers. In 2017, an ArcGIS toolbox, ACME (Automated Cirque Metrics Extraction), was developed to derive 16 cirque metrics based on input cirque outlines, threshold midpoints and DEMs. ACME has been widely used in cirque morphological analysis and regional comparisons. This paper presents a revised and extended toolbox, ACME2. This extended toolbox includes new functions to automatically derive cirque threshold midpoints (cirque foci) and 49 morphometric and locational variables, with attributes related to cirque location, size, shape, altitude, slope, and aspect, including variables related to the median axis, as well as 3 input metadata attributes. ACME2 also improves the methods for calculation of the hypsometric maximum and integral, and implements a new method for plan closure to be more consistent with the original definition. All ACME2 tools are coded in Python and can be imported into ArcGIS with user-friendly interfaces. Comparisons for 155 cirques in the English Lake District and 51 in the Shulaps Range, British Columbia, indicate consistency between the ACME2-derived and manually derived metrics, with most correlations r > 0.90: none <0.70. ACME2 provides more cirque metrics and automates the whole calculation sequence with cirque outlines and DEMs. Its comprehensive approach facilitates understanding of cirque form and development in all its variety. • We present an extended toolbox for automated cirque metrics extraction, ACME2. • ACME2 includes new functions to automatically derive cirque foci and 49 metrics. • A method for plan closure is developed to be consistent with earlier literature. • ACME2-derived and manually derived metrics are highly correlated in two test areas. • Tools and metrics can be used for the morphological study of other landforms. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tidewater glaciers can supply freshwater to fjord systems throughout winter. • Winter freshwater originates from submarine melt and subglacial discharge. • Fjord-shelf exchange processes in winter are crucial for heat influx. • Winter submarine meltwater inflow can be equivalent to or greater than in summer. • Winter freshwater preconditions the water column for the spring bloom. This review paper is the first to collect and synthesise the available knowledge, across various disciplines, on the importance of wintertime freshwater inflow from tidewater glaciers into Arctic fjords. While surface melt is limited during winter, tidewater glaciers can continue to deliver freshwater into the marine environment. This can be delivered via subglacial discharge or produced by submarine melt. Subglacial freshwater can be generated all year round through geothermal and frictional heat and delayed release of subglacially-stored freshwater. Submarine melt in Arctic fjords is caused by the presence of warm water such as Atlantic Water and its derivative coastal water masses. The dynamics of the contributing water masses are subject to varying bathymetric barriers, seasonally shifting density fronts, and external forcing such as wind or internal waves. Their impact is variable across different fjord systems. When other terrestrial water influx is limited during winter, any glacier-derived freshwater inflow into the fjords can have pronounced physical and biogeochemical consequences, even at low fluxes. These can include the generation of upwelling, but also increased stratification. The extent of the freshwater influence depends on parameters such as discharge volume flux, water depth, and depth of the glacier termini, which might in turn affect ice algae and phytoplankton production during the early spring bloom. Coupling of winter freshwater discharge from tidewater glaciers with the physical and biogeochemical conditions of the fjord is therefore a dynamic multivariable process. Rapidly changing wintertime conditions in the Arctic may already be impacting the functioning of the Arctic fjord ecosystems and necessitate efforts to understand these processes better. This review highlights the importance of wintertime freshwater by summarising the current state of knowledge about its presence and magnitude, drivers governing its inputs, as well as its potential ecological impact on fjord ecosystems. Our study uncovers knowledge gaps and proposes research directions to better understand the changing Arctic environment. [ABSTRACT FROM AUTHOR]

Subglacial processes influence the large-scale behaviour of glaciers and determine the geological processes that occur at the ice-substrate interface. In this paper we focus on subglacial deformation beneath a cold-based glacier resting on permafrost. We ask what are the drivers of subglacial permafrost deformation, how is strain distributed beneath glaciers with a permafrost substrate, how is strain transmitted from the glacier into the substrate, and how is deformed permafrost incorporated into the basal zone of the glacier? To address these questions a tunnel excavated in the margin of Wright Lower Glacier in the McMurdo Dry Valleys, Antarctica to observe the structure of the basal zone and bed of the glacier and to monitor basal ice deformation over a period of 4 years. The tunnel revealed a stacked sequence of stratified debris-bearing and clean ice layers, and thick rafts of frozen sediment. Isotopic and gas analyses reveal that despite the low local temperature of the basal ice (−18.5 °C), liquid water has played an important role in the formation of this basal sequence. The rafts of frozen sediment contain well preserved sedimentary structures and algae layers that show the material has been entrained from the underlying permafrost. Deformation measurements made with a combination of displacement transducers, strain arrays, and plumb-lines show that strain and motion within the basal zone are heterogeneous and that strain is transmitted through the permafrozen sediment and into intra-sediment ice layers. The distribution of strain in the basal zone produces a compound velocity profile resembling the deformation patterns inferred from deformation structures in Pleistocene permafrost and also resembles profiles associated with subglacial sediment deformation driven by hydrogeological processes. We conclude that ice-rich permafrost is readily deformed by glaciers and that there is no clear boundary between basal ice and deforming permafrost. [ABSTRACT FROM AUTHOR]

Glacial cirques are armchair-shaped erosional hollows, typified by steep headwalls and, often, overdeepened floors. They reflect former regions of glacier initiation, and their distribution is, therefore, linked to palaeoclimate. Because of this association, cirques can be analysed for the information they provide about past environments, an approach that has a strong heritage, and has seen resurgence over recent years. This paper provides a critical assessment of what cirques can tell us about past environments, and considers their reliability as palaeoenvironmental proxies. Specific focus is placed on information that can be obtained from consideration of cirque distribution, aspect, altitude, and morphometry. The paper highlights the fact that cirques potentially provide information about the style, duration and intensity of former glaciation, as well as information about past temperatures, precipitation gradients, cloud-cover and wind directions. In all, cirques are considered a valuable source of palaeoenvironmental information (if used judiciously), particularly as they are ubiquitous within formerly glaciated mountain ranges globally, thus making regional or even global scale studies possible. Furthermore, cirques often occupy remote and inaccessible regions where other palaeoenvironmental proxies may be limited or lacking. [ABSTRACT FROM AUTHOR]

This paper briefly reviews the physical and human geography of the Kamchatka region and summarises previous research on Holocene climate dynamics. We provide context for the rest of the Special Issue of the Journal Global and Planetary Change entitled ‘Holocene climate change in Kamchatka’, the primary focus of which is the use of lake sediment records for palaeoclimatic inferences. In this paper an additional perspective from ongoing tree ring, ice core and borehole temperature reconstructions illustrates that the Kamchatka region is rich in paleoclimatic proxies. The period of the last 200 years is sufficiently covered by the proxy information, including reconstructions with annual resolution. In this period the tree-rings, ice cores, boreholes, and glacier fluctuations recorded a 1 °C warming and a general glacier retreat, i.e. the transition from the Little Ice Age climate to the modern one. Although the proxies have different resolution, accuracy and seasonality in general they demonstrate a coherent picture of environmental changes in the last two centuries. The tree ring and ice core records are up to four-six hundred years long and they provide information on annual to decadal variability of summer temperature, accumulation processes, volcanic eruptions and lahar activity. [ABSTRACT FROM AUTHOR]

• Proglacial runoff is attenuated by a supraglacial debris cover. • Diurnal hydrographs are confined to warmer than average conditions. • Supraglacial debris causes elevated bicarbonate concentrations. • Inefficient subglacial drainage causes high bicarbonate and sulphate concentrations. • The time from peak air temperature to discharge is longer than for clean glaciers. Debris is known to influence the ablation, topography and hydrological systems of glaciers. This paper determines for the first time how these influences impact on bulk water routing and the proglacial runoff signal, using analyses of supraglacial and proglacial water chemistry and proglacial discharge at Miage Glacier, Italian Alps. Debris does influence the supraglacial water chemistry, but the inefficient subglacial system beneath the debris-covered zone also plays a role in increasing the ion contribution to the proglacial stream. Daily hydrographs had a lower amplitude and later discharge peak compared to clean glaciers and fewer diurnal hydrographs were found compared to similar analysis for Haut Glacier d'Arolla. We attribute these observations to the attenuating effect of the debris on ablation, smaller input streams on the debris-covered area, a less efficient subglacial system, and possible leakage into a raised sediment bed beneath the glacier. Strongly diurnal hydrographs are constrained to periods with warmer than average conditions. 'Average' weather conditions result in a hydrograph with reverse asymmetry. Conductivity and discharge commonly show anti-clockwise hysteresis, suggesting the more dilute, rapidly-routed melt component from the mid-glacier peaks before the discharge peak, with components from higher up-glacier and the debris-covered areas arriving later at the proglacial stream. The results of this study could lead to a greater understanding of the hydrological structure of other debris-covered glaciers, with findings highlighting the need to include the influence of the debris cover within future models of debris-covered glacier runoff. [ABSTRACT FROM AUTHOR]

The paper concerns ice dams and glacial lake outburst floods (GLOFs) in the Karakoram. Some 146 events are identified, including 30 major disasters. Large downstream populations and major infrastructure are threatened. Risk factors differ from recent reports of other Himalayan GLOFs associated with glacier recession and global warming. Ice dams are largely or entirely active ice, put in place by advancing glaciers. Climate change is a factor, but the ice cover in the Karakoram has been sustained, and even some increase in mass. Surge-type glaciers comprise or affect~70% of our inventory. The most frequent, large GLOFs come from local clusters of glaciers in five sub-basins, given special attention here. In four there were new ice dams formed since 2008 and two generated dangerous GLOFs. An urgent need arises to track short-term ice and lake behavior and how surge dynamics may be involved. Satellite images and DEMs are employed in cross-correlation feature tracking and elevation change respectively. The glaciers of interest all exhibit irregular movement, including recent advances, but with great variability and no clear relation to climatic fluctuations. • Study updates inventory of ice dams and related GLOFs in the Karakoram. • Study reports recent evidence of surface displacement and elevation changes of glaciers involved in ice dam generation. • Surge-type glaciers comprise or affect ~70% of inventory of ice dams and related GLOFs. • Four glaciers formed new ice dams since 2008, two (Kyagar, Khurdopin) generating dangerous GLOFs. • The studied glaciers exhibit irregular movement, but with great variability and no clear relation to climatic fluctuations. [ABSTRACT FROM AUTHOR]

In recent years, increasing moisture over the Arctic and subarctic regions shows that the Arctic is experiencing wetting conditions, and poleward atmospheric moisture transport (PAMT) plays a vital role in the atmosphere-ice/snow interactions in the Arctic. To identify the effect of PAMT on the surface energy balance (SEB) for the Arctic glacier, meteorological data from an automatic weather station (AWS) at 377 m a.s.l. on the Austre Lovénbreen glacier, as well as the ERA5 reanalysis data from 30 April 2014 to 30 April 2015, were analyzed in this paper. Our results show that the net shortwave radiation (S net) (18 W m−2, 55%), turbulent sensible (H) (14 W m−2, 43%) and subsurface heat flux (G) (1 W m−2, 2%) act as the energy sources, while the net longwave radiation (L net) (−19 W m−2, 56%), melt energy (Q m) (−12 W m−2, 35%) and turbulent latent heat flux (LE) (−3 W m−2, 9%) represent the heat sink. The development process of Atmospheric River (AR), primary form of PAMT, near the Svalbard in February 2015 was revealed according to the total column water vapor, 850 hPa winds and geopotential height fields. Compared to summer, the glacier SEB was more affected in winter by PAMT, leading to a frequent overcast and thus increasing air temperature, moisture, and wind speed, all of which are variables governing the SEB by decreasing H, LE and G less than increasing the L net. Our findings obtained here can help to better understand the diverse SEB change on the high Arctic glacier from the perspective of PAMT and large-scale atmospheric circulations anomalies. [ABSTRACT FROM AUTHOR]

Studies on long-term fluctuations in glacier volume and mass are crucial for understanding past climate change. In this paper, we utilized Picea schrenkiana to develop a 525-year chronology of latewood blue intensity (LWBI) in the Tianshan Mountains. Relying on temperature as the main controlling factor for tree growth and glacier mass balance (GMB) variations, the LWBI chronology was used to reconstruct the summer temperature (JJA, R 2 adj = 47%) and the annual glacier mass balance (annual GMB, R 2 adj = 39%) in the Tianshan Mountains over the past 400 years. The reconstruction results show that the rapid warming since 1974 has caused the Tianshan No.1 glacier (TS No.1) to experience an unprecedented melting trend within the last four centuries. It is disturbing that the glacier still remain in an ablation state for the next 80 years under both representative concentration paths (RCP) 4.5 and 8.5 scenarios, which will exacerbate the adverse environmental impacts of glacial hazards. Our study provides a continuous record for glacier research in high mountains Asian and contributes to a more detailed assessment of glacier and climate change in this region. The spatial correlation analysis of the PC1 and the ERA5 grid temperature dataset after the original (a), detrended (b) and first-order difference (c) calculations in the verification period (1950–2005), all insignificant correlations (P > 0.05) were masked out, where A represent the Tianshan Mountains (this study), B represent Central Europe Alps (Büntgen et al., 2006), C represent East Asia (Davi et al., 2002), D represent Dunde ice core (Thompson et al., 2006), and E represent Guliya ice core (Thompson et al., 1997). Comparison of Tianshan temperature reconstruction (PC1) with other MXD-based temperature reconstructions, where (d) is the comparison between PC1 and Central European Alps summer (June to September) temperature reconstruction, (e) is the comparison between PC1 and East Asian Japanese warm season (May to September) temperature reconstruction, and (f) is the comparison between PC1 and Northern Hemisphere summer (June to August) temperature reconstruction (Schneider et al., 2015). (g) is the comparative between the PC1 and Atlantic multidecadal variability (AMV, Wang et al., 2017). Comparison of TS No.1 GMB reconstruction with ice core accumulation data, where (h) is the comparison between TS No.1 GMB reconstruction and Dunde ice core water equivalent net balance (accumulation, 5-year average), (i) is the comparison between TS No.1 GMB reconstruction and Guliya ice core water equivalent net balance (accumulation, 10-year average). All comparison series are Z-score normalized and low-pass filtered with a step size of 10 years (ice core accumulation data are 5 year) to achieve low-frequency fluctuations. [Display omitted] • A 525-year latewood blue intensity (LWBI) chronology was developed to study glacial dynamics for the Tianshan Mountains. • The results showed that the last 20 years to be outside the range of natural variability of the last 400 years. • The Tianshan No. 1 glacier will continue to melt rapidly in the next 80 years under the RCP 4.5 and 8.5 scenarios. [ABSTRACT FROM AUTHOR]

Cirques are typical erosional landforms of glaciers and have been used as bases for paleoclimate and paleoenvironment reconstruction and for understanding the interactions between glacial erosion, climate, and topography. The availability of high-resolution digital elevation models (DEMs) provides the opportunity to map large populations of cirques for regional and global scale analysis. However, cirque outlines are still mainly determined based on manual digitization, which is time consuming and labor intensive. This paper introduces an automated method to recognize and delineate cirques using DEMs based on a series of hydrological and morphological analyses, including delineating stream network, filtering streams, determining potential cirque threshold points, and delineating cirque outlines. A semi-automated tool is also developed based on user-specified threshold points or cross sections. The related tools are coded in python and imported into ArcGIS as a toolbox, AutoCirque, with user friendly interfaces. Comparison in a test area of the eastern Tian Shan, China, indicated that the population statistics are relatively consistent between manually digitized and auto-delineated cirques. Detailed comparisons for 11 selected cirques indicated that the AutoCirque-delineated and manually digitized cirque outlines are similar in shape with an average boundary offset of approximately one DEM cell size (30 m) and a 70–90% overlap-fit percentage. The derived cirque metrics are also similar, especially for elevation, slope, and aspect related metrics. This toolbox can significantly speed up the analytical processes, remove the subjectivity in delineating cirque outlines, and allow for the comparison of cirque morphology and metrics at regional and global scales. • This paper presents an automated method to delineate cirque outlines from DEMs. • The developed ArcGIS toolbox incudes both fully automated and semi-automated tools. • Delineated cirques have consistent population statistics with manual-digitized ones. • Manual- and auto-derived cirques are similar in shape with high overlap percentage. • This toolbox allows for large population analyses of cirques at different scales. [ABSTRACT FROM AUTHOR]

Abstract Ice-contact deposits emplaced by Late Paleozoic Ice Age (LPIA) glaciers are rarely exposed due to a low degree of preservation and their capping by thick glaciomarine deglaciation sequences. In this paper, we present new data on glacial cyclicity, relative age constraints and paleoice flow interpretations for an ice-contact succession of the lowermost Itararé Group in eastern Paraná Basin (Brazil). The 80 m-thick ice-contact complex rests over the Itararé Group basal unconformity and comprises four stacked informal stratigraphic units regarded as the depositional/deformational record of three ice lobes advance/retreat cycles. Glacial cycle 1 comprises a sheet of massive diamictite resting on striated pavements carved on Devonian sandstones and topped by grooved/fluted surfaces, which indicate subglacial emplacement from a northward flowing ice lobe. The glacial cycle 2 succession was deposited in a proglacial to ice-marginal marine setting and subsequently deformed due to minor ice margin fluctuations of a westward/southwestward flowing grounded ice lobe. Glacial cycle 3 is interpreted as a thick overridden push moraine composed of grounding-line fan deposits capped by a subglacial diamictite emplaced by grounded ice advancing northwestward. A middle Visean-early Serpukhovian palynomorph assemblage was recorded in cycle two deposits, representing the oldest late Paleozoic glacial rocks in the Paraná Basin. The ice-contact complex elucidates multiple waxing and waning phases of the Windhoek Ice Sheet onto the eastern margin of the Paraná Basin during the Mississippian-Early Pennsylvanian, demonstrating that ice sheets of the early stages of the LPIA were also present in the Brazilian-African domain of southwestern Gondwana. Highlights • 3 glacial cycles with variable ice lobe kinematics are defined for an ice-contact complex in the lowermost Itararé Group. • The basal age of the Itararé Group is older than previously interpreted ranging from the middle Visean. • Ice sheets covered the west-central domain of Gondwana during the Mississippian. [ABSTRACT FROM AUTHOR]

Abstract Kuannersuit Glacier in west Greenland experienced a major surge in 1995–1998, where the glacier advanced 10.5 km down-valley. In this paper, we examine how the quiescent phase has progressed until 2015 with respect to ice dynamics, landform formations and glaciomorphological changes. In the initial quiescent phase (2001–2005), ice velocities along the center flowline were 37–55% higher than ice velocities (6.3–9.0 m yr−1) in 2005–2015, and a linear relationship between ice velocity and distance from the glacier front, which existed during the initial quiescent phase, had disappeared in 2005–2015. Between 2001 and 2015, the post-surge glacier tongue thinned by 84.0 ± 6.3 m, equal to 6.0 ± 0.5 m yr−1. The 30-m high terminal moraine detached from the active glacier along the uppermost thrust band between 2005 and 2015, after which the glacier front receded 1.5 km. Between the terminal moraine and the glacier front, observations suggested that a proximal outwash plain was forming on top of glacier ice and that glacier naled (icing, aufeis) was incorporated into the outwash plain. In less dynamic areas with gently sloping topography along the lateral glacier margins, crevasse-squeeze ridges were melting out. The most prominent glaciomorphological feature in 2015 was a c. 1-km long gorge with c. 30–40 m high ice cliffs. This gorge had formed into the glacier front, following the collapse of a series of chasms above the main subglacial channel. Roof collapse processes above subglacial channels had a significant impact on the glacier's mass loss and on the glaciomorphology during the quiescent phase. Earlier observations from 1913 suggest that the formation of this gorge is a reoccurring phenomenon during the quiescent phase. A lower pothole field on the glacier tongue that existed during the initial quiescent phase had completely disappeared in 2015, while a larger upper pothole field in the reservoir area prevailed. During the initial quiescent phase, the subglacial drainage system developed into a stable channelized network, although a jökulhlaup from a large ice-dammed lake occurred. This single event was dated to have occurred between 11 and 13 August 2006, and the lake did not refill. The spatiotemporal association and evolution of glacial and glaciomorphological landforms at Kuannersuit Glacier are likely similar to processes at many other surging and rapidly receding glaciers of similar size. [ABSTRACT FROM AUTHOR]

Abstract Nature-based tourism directly and indirectly affects the flora, fauna and environment, thereby reducing the sustainability of tourism destinations. However, the impact of tourism activities on glaciers at glacial tourism sites remains unexplored. Using two typical glacial tourism sites in China as examples, this paper uses the tourism heat footprint (THF) method to examine the impact of large-scale tourism activities on glaciers via local average temperatures. The THF method measures anthropogenic heat release (AHR) from energy consumption and human metabolism per unit area and time divided into seven components of tourism activities: transportation, accommodation, sightseeing, catering, entertainment, shopping and waste disposal. The main results show that the THF values of the Yulong and Hailuogou tourism zones are exhibiting a rapid growth trend, increasing from 8.7 × 10−3 and 4.0 × 10−4 Wm−2 in 1990 to 3.6 and 3.0 × 10−1 Wm−2 in 2017, respectively. These THFs are exerting a significant cumulative effect on the retreat of glaciers by increasing local average temperatures in conjunction with global climate change. These results show that the sustainability of glacial tourism and destinations is threatened by large-scale tourism activities. This study fills a current research gap, enriches the understanding of the impact of tourism activities on glacial resources and expands the analytical perspective of sustainable tourism research. Moreover, this study provides decision support for managing glacial scenic destinations and for the sustainable development of glacial tourism. Highlights • The THF values of the Yulong and Hailuogou increased sharply during 1990–2017. • Tourism activities cumulatively affected glacial retreat via rising temperatures. • The sustainability of glacial tourism and destinations is threatened. • This study enriches existing understanding of tourism's impact on glaciers. [ABSTRACT FROM AUTHOR]

Abstract High elevation or high latitude hydropower production (HP) strongly relies on water resources that are influenced by glacier melt and are thus highly sensitive to climate warming. Despite of the wide-spread glacier retreat since the development of HP infrastructure in the 20th century, little quantitative information is available about the role of glacier mass loss for HP. In this paper, we provide the first regional quantification for the share of Alpine hydropower production that directly relies on the waters released by glacier mass loss, i.e. on the depletion of long-term ice storage that cannot be replenished by precipitation in the coming decades. Based on the case of Switzerland (which produces over 50% of its electricity from hydropower), we show that since 1980, 3.0%–4.0% (1.0–1.4 TWh yr−1) of the country-scale hydropower production was directly provided by the net glacier mass loss and that this share is likely to reduce substantially by 2040–2060. For the period 2070–2090, a production reduction of about 1.0 TWh yr−1 is anticipated. The highlighted strong regional differences, both in terms of HP share from glacier mass loss and in terms of timing of production decline, emphasize the need for similar analyses in other Alpine or high latitude regions. Graphical abstract Image 1 Highlights • First quantification of Alpine hydropower production share from glacier mass loss. • Since 1980, 1.0 to 1.4 TWh yr-1 of Swiss hydropower comes from glacier mass loss. • Expected country-scale production reduction by 2070–2090 of 1.0 TWh yr-1. • Notable regional differences despite of continuous retreat of all Swiss glaciers. [ABSTRACT FROM AUTHOR]

Highlights • Debris-covered glaciers have a distinct hydrological structure. • Debris cover reduces supraglacial catchment size and reduces melt rates. • Beneath continuous debris on the lower glacier the drainage network is inefficient. • An efficient conduit system drains the clean and dirty ice on the upper glacier. • A channelized and distributed system co-exist beneath the lower glacier. Abstract Supraglacial debris is known to strongly influence the distribution of glacier surface melt. Since melt inputs drive the formation and evolution of glacial drainage systems, it should follow that the drainage systems of debris-covered glaciers will differ from those of debris-free glaciers. This would have implications for the proglacial runoff regime, subglacial erosion and glacier dynamics. This paper presents analysis of return curves from 33 successful dye injections into the extensively debris-covered Miage Glacier, Italian Alps. It demonstrates that the spatial distribution of supraglacial debris influences the structure and seasonal evolution of the glacial drainage system. Where the debris cover is continuous, melt is lower and the surface topography is chaotic, with many small supraglacial catchments. These factors result in an inefficient englacial/subglacial drainage network beneath continuous debris, which drains to the conduit system emanating from the upper ablation zone. Melt rates are high in areas of clean and dirty ice above the continuous debris. Runoff from these areas is concentrated by inter-moraine troughs into large supraglacial streams, which encourages the early-season development of an efficient englacial/subglacial conduit system downstream of this area. Drainage efficiency from the debris-covered area increases over the melt season but dye-trace transit velocity remains lower than from moulins on the upper glacier. Future runoff models should account for the influence of supraglacial debris on the hydrological system. [ABSTRACT FROM AUTHOR]

Abstract The Cryosphere has been undergoing a worldwide retreat, as seen in the decrease in the areal extent and volume of glaciers and in the areal extent of permafrost. This paper presents a systematic examination of the inherent stability changes of glaciers and permafrost caused by warming. Various study results suggest that over the past 30 years, the internal temperature of glaciers and permafrost exhibits an overall accelerating warming trend. The warming rate peaked in the mid-2000s and slowed slightly for several years afterward. In recent years, however, the warming rate has seemed to pick up again. The warming of glaciers and permafrost has exerted great impact on their stability, displayed as intensified melting, increased glacier surging, enlargement of supraglacial lakes, and increased permafrost degradation. Even without a future temperature increase, some glaciers will continue to shrink, and the number of surging glaciers will increase. The transition from low-temperature to high-temperature permafrost is a noticeable warning sign of a comprehensive degradation of permafrost. These results indicate that "warming" glaciers and permafrost will exert significant impacts on the hydrology, ecology, and stability of engineering in cold regions. [ABSTRACT FROM AUTHOR]

The Viedma glacier is the largest glacier in Argentina and one of the most dynamic in the Southern Patagonian Icefield. It is a strategic water source. This study analyzes the interactions of glaciological variables that help better explain the behavior of the Viedma glacier. This paper presents the study of surface flow speed and ice surface temperatures during the 2015–2016 warm season by using remote sensing data and includes the statistical correlation between those variables. In addition, a reconstruction of the front fluctuation between 1979 and 2016 through CORONA and LANDSAT images is included. Finally, the displacement modes dominating the Viedma glacier are suggested. Our results showed that the mean surface flow speed during the study period was of around 1.2 ± 0.3 md −1 and reached maximum values of 5.5 ± 0.3 md −1 and 3 ± 0.3 md −1 at middle basin and terminus respectively. Thermal data revealed minimum values of −2 °C in the uppermost section of the study area, whilst the glacier's terminus showed supraglacial melt (values above pressure melting point). Front fluctuation analysis revealed the largest front retraction of the last 40 years between 2010 and 2016: around 281 my −1 . Statistical correlation analysis and glaciological data suggested that the middle and lower basins of the Viedma glacier are widely dominated by basal sliding. [ABSTRACT FROM AUTHOR]

Glacier melt water is an important water resource in arid regions of central Asia during the dry seasons, and it is very susceptible to climate disturbances. In this paper, based on the glacier datasets of the first and second Chinese Glacier Inventories, the glacier change in the Chinese Tien Shan from 1960s to 2010 was quantify by assessing the Annual Percentages of Area Changes ( APAC ), Annual Percentages of Volume Changes ( APVC ), and Equilibrium Line Altitude ( ELA ). The results indicated that the mean glacier area and mean glacier volume decreased by 0.7% ± 0.6% per year and 0.83% ± 0.73% per year in the Chinese Tien Shan during the period of 1960–2010, respectively. The mean ELA increased by 24.87 ± 126.84 m during the study period. In addition, we also found that the glacier retreat in the Bogda Mountains was the fastest, mainly due to the sensitivity of small glaciers to climate change, with an APAC of −0.86% ± 0.49% per year and APVC of −1.04% ± 0.55% per year, and the mean ELA increased by 44.35 ± 55.07 m. Moreover, increases in both air temperature (in terms of Thawing Degree-Day (TDD) and Freezing Degree-Day (FDD)) and precipitation were found over the study area during the past five decades. However, such increases in precipitation did not result in any significant changes in the ratio of annual snowfall to total precipitation (S/P) across the Chinese Tien Shan Mountains. Hence, the glacier shrinkage mainly resulted from the significant increase in TDD and FDD in the study region. [ABSTRACT FROM AUTHOR]

Highlights • Threats to symbolic landscapes can also constitute threats to identity and cultural continuity. • Natural hazards are conceptualised in a hierarchy of risk types, including socio-cultural threats. • Attachment to place can influence the ways risk is socially and culturally constructed. • Cultural factors can both enable and constrain the capacities necessary for responding to risk. Abstract Mountain peoples are increasingly impacted by environmental changes, including the rapid retreat of glaciers and the growth of dangerous glacial lakes that can breach their natural dams and flood downstream communities. Despite considerable research assessing glacial lake hazards, there have been relatively few attempts to explore the socio-cultural and psychological dimensions of this type of risk. Further, environmental changes become intermeshed with other types of broad-scale changes that have local scale implications in the lived experience of rural mountain communities. This paper examines risk through the lens of those who are directly impacted by such processes. Ethnographic techniques were used, including interviews with community members from the case study in a sacred valley of Nepal that lies downstream from a large and potentially dangerous glacial lake, Tsho Rolpa. The Rolwaling Sherpa community's enduring attachment to their valley and their desire for cultural continuity amidst social, economic, and environmental changes have influenced their interpretations of risk and shaped their responses in complex ways. Findings indicate that threats to their landscape also constitute threats to their self-understanding and their subjective notions of well-being, which are bound up in the meaning of their place. This case study demonstrates the additional insight that can come from contextualizing disaster risk in a way that acknowledges local people's subjective interpretations, priorities, and values. This is expected to be especially critical in cases where sacred or culturally significant landscapes are threatened by global environmental changes. [ABSTRACT FROM AUTHOR]

Mega-scale glacial lineations (MSGLs) are ridge-groove corrugations aligned in the direction of the former ice flow, tens of kilometers long and up to a few hundred meters wide. They are the most striking subglacial features on the beds of former ice streams and play an important role in modulating ice flow through their influence on bed roughness and subglacial hydrology. Despite the importance of MSGLs, their formation remains enigmatic. Most studies have tended to focus on assemblages of MSGLs and their relationship to other landforms up-ice (e.g. drumlins or bedrock features in ice stream onset zones) but fewer studies have examined their characteristics and transition to other landforms towards ice stream grounding lines. In this paper we investigate the relationship between an assemblage of MSGLs and ploughmarks on the bed of the former Bjørnøyrenna Ice Stream in the SW Barents Sea, which occurs in the central part of the ice stream bed. A sample of MSGLs is used to test their potential origin, based on their metrics (width, length) and diagnostic characteristics predicted by formation theories. Results show a down-flow depth decrease of the MSGL grooves, and a shallowing tendency once they transition into ploughmarks. Their width shows an increasing tendency, which we link mostly to the strong divergence of the trough (and ice flow) downstream. The prominent continuity from linear to curvilinear features demonstrates that the grooves associated with MSGLs transition into iceberg ploughmarks. This observation is consistent with the hypothesis that the MSGLs have formed through a mechanism of “groove-ploughing”, at least in part. The continuity from MSGLs to iceberg ploughmarks resulted from detachment of large icebergs from the grounded ice wall or grounded ice shelf and their ploughing away from the ice margin. [ABSTRACT FROM AUTHOR]

Fast-flowing ice streams and outlet glaciers exert a major control on glacial discharge from contemporary and past ice sheets. Improving our understanding of the extent and dynamic behaviour of palaeo-ice streams is crucial for predictions of how the cryosphere will respond to climate warming and the associated implications for global sea level. This paper presents results from two 3D-seismic surveys located on the continental shelf adjoining the Disko Bay Trough Mouth Fan (TMF), one of the largest glacial outlet systems in Greenland. Located at the seaward terminus of the c. 370 km long cross-shelf Disko Trough, the Disko Bay TMF was generated by highly efficient subglacial sediment delivery onto the continental slope during repeated ice stream advances. A variety of submarine glacial landform assemblages are recognised on the seabed reflecting past ice stream activity. The 3D-seismic study covers the shallow banks located north and south of the Disko Trough and sheds focus on the seabed and the uppermost stratigraphic interval associated with the late Pleistocene development. The buried section (probably of Saalian age) contains a prominent grounding-zone wedge (GZW) in the northern and low-angle progradational packages in the southern area, indicating a period of major glacial advances to the shelf margin. Subsequently, the outer margin was influenced by glacimarine sedimentation, localized shelf-edge ice advances and sediment transport by contour currents that possibly began in the last interglacial period (Eemian). During the last (de)glaciation, the northern bank appears to have been covered by passive ice leaving a field of dead-ice deposits. In contrast, multiple sets of terminal moraine ridges observed on the southern bank suggest a slow retreat of active, grounded ice from the Last Glacial Maximum (LGM) position on the outer shelf. Isostatic and tectonic influences on relative sea level may have played a role in generating the divergent glacial configurations of the northern and southern bank areas. [ABSTRACT FROM AUTHOR]

Glaciers covered by debris are widespread in the Himalayas. Debris layer makes the melting process of glaciers complicated, and the correlation between the spatial melt differences of glacier and its surface features is still not clear. The aim of this study was to identify possible causes of thickness changes for Himalayan debris-covered glaciers. Firstly, three high resolution Digital Elevation Model (DEM) datasets including SRTM DEM, AW3D and TanDEM-X DEM were used to estimate glacier thickness changes from 2000 to 2013. By checking and removing geometric displacements, systematic deviations and elevation-related bias, as well as correction of radar wave penetration depth in the clean glacier areas, reliable thickness change information in this complex glaciated region were provided. Then debris thicknesses on the glaciers were estimated. The surface lowering caused by ice cliffs or supraglacial ponds significantly reduces debris thickness. Finally, some surface features including debris thicknesses, spatial patterns of supraglacial ponds and ice cliffs extracted from high-resolution satellite images in different times, were comprehensively used to evaluate the main drivers of glacier melting differences. Results demonstrate that spatial variability of glacier melting in Himalayas is caused by the combined effects of debris thicknesses, ice cliffs and supraglacial lakes, with different dominant factors for different regions. The thickened glacier region, which mostly appears above 5300 m a.s.l., with minimal debris cover, displayed large patches of thickening and partial serious thinning in the debris-free areas. Although the thick debris layer (> 0.20 m) would slow down the glacier melting at the low-elevations, it leads to the heavy glacier thinning for the regions located 5000–5300 m a.s.l., where there are dense ice cliffs. In some areas with >1 m of average debris thickness, glaciers have thinned slowly because of erosion from the ice cliffs or large supraglacial ponds. Area and number of cliffs have proven to be key factors in controlling regional ablation for debris-covered glaciers, and supraglacial lakes serve as assistance. • This paper offers clues for the explanation of debris cover anomaly. • The thickness changes of debris-covered glaciers are highly heterogeneous. • The dominant factors of thickness change are different for different zones. • Ice cliff is the key to glacier ablation, and ponds serve as assistance. [ABSTRACT FROM AUTHOR]

• Recent geochronological findings are not engaged, leading to a different conclusion. • Alluviation during ca. 26–11 ka is not supported by radiocarbon dates. • Interpretation of some sediments and processes should be reconsidered. In a study where one of the objectives was to assess the impact of climate change on evolution of an alluvial fan, the authors determined some geochronological data that enabled them to discuss paleoenvironmental conditions of the Czarny Dunajec River system. They conclude that the gravelly material stored in the fan was deposited probably between c. 27 and 14 ka BP, MIS 2, and link this period of deposition with the glacier development in the Tatra Mountains. The geochronological data presented in their paper, however, does not support largely this statement, also the discussion does not take into account the newest findings in the region, which disprove the presumed connection between alluvium deposition and glacial stages. Additionally, some data on river terraces and alluvial sediments requires clarification, i.e. number of terraces and their heights, straths and the composition of terrace deposits, and the processes from which sediments and the fan originate. [ABSTRACT FROM AUTHOR]

Understanding the geomorphology left by waxing and waning of former glaciers and ice sheets during the late Quaternary has been the focus of much research. This has been hampered by the difficulty in dating such features. Luminescence has the potential to be applied to glacial sediments but requires signal resetting prior to burial in order to provide accurate ages. This paper explores the possibility that, rather than relying on light to reset the luminescence signal, glacial processes underneath ice might cause resetting. Experiments were conducted on a ring-shear machine set up to replicate subglacial conditions and simulate the shearing that can occur within subglacial sediments. Luminescence measurement at the single grain level indicates that a number (albeit small) of zero-dosed grains were produced and that these increased in abundance with distance travelled within the shearing zone. Observed changes in grain shape characteristics with increasing shear distance indicate the presence of localised high pressure grain-to-grain stresses caused by grain bridges. This appears to explain why some grains became zeroed whilst others retained their palaeodose. Based on the observed experimental trend, it is thought that localised grain stress is a viable luminescence resetting mechanism. As such relatively short shearing distances might be sufficient to reset a small proportion of the luminescence signal within subglacial sediments. Dating of previously avoided subglacial sediments may therefore be possible. [ABSTRACT FROM AUTHOR]

Supraglacial debris complicates the melting state of debris-covered glaciers, and whether debris increases or decreases the rate of glacier melt is ambiguous according to different observations. In this paper, we aim to determine the potential factors that influence changes in thickness of debris-covered glaciers. First, we present the thickness changes of a large debris-covered glacier in the Tienshan Mountain using high-resolution Digital Elevation Model (DEM) data from three periods in 2000, 2009 and 2013. It is shown that the thickness changes differ greatly over the debris-covered portions of the glacier. These debris-covered regions can be divided into three parts along the glacier axis according to the rate of thickness change. Specifically, these parts include the zone of minimal change, the zone of heavy thinning, and the zone of slight thinning. Detailed information on the closely related factors, including the debris thickness, which was measured across the whole glacier during our field work, and the presence of ice cliffs and supraglacial lakes detected on high-resolution satellite images, are combined to determine the reasons for the differences in melting state among the three zones. The results show that the thickness changes of the debris-covered glacier are jointly influenced by debris thickness and the presence of ice cliffs and supraglacial lakes; moreover, the dominant factor differs among the different zones. The critical debris thickness, which mostly appears in the minimal change zone and accelerates glacier melting, as confirmed through field observations, is not associated with glacier thinning because its location is close to the accumulation zone. The regions where the rates of thinning are greatest coincide with the regions where the ice cliffs are densest. Where the debris is thicker than 1 m on average, the glacier is still thinning slightly due to the presence of ice cliffs and lakes. It is proven that the quantity and area of the ice cliffs and supraglacial lakes is the key to understanding the melting rate of debris covered glacier. [ABSTRACT FROM AUTHOR]

This paper presents a Glacier Termini Tracking (GTT) toolbox for the two-dimensional analysis of glacier-terminus position changes. The input consists of a vector layer with several termini lines relating to the same glacier at different times. The output layers allow analyses to be conducted of glacier-terminus retreats, changes in retreats over time and along the ice face, and glacier-terminus fluctuations over time. The application of three tools from the toolbox is demonstrated via the analysis of eight glacier-terminus retreats and fluctuations at the Hornsund fjord in south Svalbard. It is proposed that this toolbox may also be useful in the study of other line features that change over time, like coastlines and rivers. The toolbox has been coded in Python and runs via ArcGIS. [ABSTRACT FROM AUTHOR]

On 17 October 2015, a landslide of roughly 60 × 10 6 m 3 occurred at the terminus of Tyndall Glacier in Taan Fiord, southeastern Alaska. It caused a tsunami that inundated an area over 20 km 2 , whereas the landslide debris itself deposited within a much smaller area of approximately 2 km 2 . It is a unique event in that the landslide debris was deposited into three very different environments: on the glacier surface, on land, and in the marine waters of the fjord. Part of the debris traversed the width of the fjord and re-emerged onto land, depositing coherent hummocks with preserved source stratigraphy on an alluvial fan and adjacent moraines on the far side of the fjord. Imagery from before the landslide shows that the catastrophic slope failure was preceded by deformation and sliding for at least the two decades since the glacier retreated to its current terminus location, exposing steep and extensively faulted slopes. A small volume of the total slide mass remains within the source area and is topped by striated blocks (> 10 m across) and standing trees that were transported down the slope in intact positions during the landslide. Field work was carried out in the summer of 2016, and by the time this paper was written, almost all of the supraglacial debris was advected into the fjord and half the subaerial hummocks were buried by glacial advance; this rapid change illustrates how highly active sedimentary processes in high-altitude glacial settings can skew any landslide-frequency analyses, and emphasizes the need for timely field investigations of these natural hazards. [ABSTRACT FROM AUTHOR]

This paper presents detailed elevation and volume analysis of 16 individual glaciers, grouped at four locations, spread across the Antarctic Peninsula (AP). The study makes use of newly available WorldView-2 satellite stereo imagery to exploit the previously untapped value of archival stereo aerial photography. High resolution photogrammetric digital elevation models (DEMs) are derived to determine three-dimensional glacier change over an unprecedented time span of six decades with an unparalleled mean areal coverage of 82% per glacier. The use of an in-house robust surface matching algorithm ensured rigorous alignment of the DEMs to overcome inherent problems associated with processing archival photography, most notably the identification and correction of scale error in some datasets. The analysis provides insight into one of the most challenging and data-scarce areas on the planet by expanding the spatial extent north of the AP to include previously un-studied glaciers located in the South Shetland Islands. 81% of glaciers studied showed considerable loss of volume over the period of record. The mean annual mass loss for all glaciers yielded 0.24 ± 0.08 m.w.e. per year, with a maximum mass loss of up to 62 m.w.e. and frontal retreat exceeding 2.2 km for Stadium Glacier, located furthest north on Elephant Island. Observed volumetric loss was broadly, though not always, correlated with frontal retreat. The combined mass balance of all 16 glaciers yielded − 1.862 ± 0.006 Gt, which corresponds to − 0.005 mm sea level equivalent (SLE) over the 57 year observation period. [ABSTRACT FROM AUTHOR]

Rias are the drowned mouths of unglaciated valleys, usually bordered by steep slopes rising to mountains, hills, or plateaux. They are formed on rocky coasts. This paper examines many of the features of rias and ria coastlines, discussing their definition, their distribution (which is greater than previously thought), their morphologies, and some of the potential controls on their distribution, including tectonic history and tidal range. Notable clusters occur in Australia, south east Asia, East Asia, Oceania, eastern Africa, Oman, parts of South America (Argentina, Colombia, Brazil and Venezuela), Crimea, and the Mediterranean and Black Sea basins. The finest examples occur in areas with high tidal ranges. [ABSTRACT FROM AUTHOR]

This paper presents data from 42 new samples yielding Late Pleistocene cosmogenic 10 Be and 36 Cl exposure ages of moraine boulders across a series of glaciated valleys in the Toubkal Massif (4167 m a.s.l.), High Atlas, Morocco. This represents the first comprehensive Pleistocene glacial chronology in North Africa and one of the largest datasets from the Mediterranean region. The timing of these glacier advances has major implications for understanding the influence of Atlantic depressions on moisture supply to North Africa and the Mediterranean basin during the Pleistocene. The oldest and lowest moraines which span elevations from ∼1900 to 2400 m a.s.l. indicate that the maximum glacier advance occurred from MIS 5 to 3 with a combined mean 10 Be and 36 Cl age of 50.2 ± 19.5 ka (1 SD; n = 12, 7 outliers). The next moraine units up-valley at higher elevations (∼2200–2600 m a.s.l.) yielded exposure ages close to the global Last Glacial Maximum (LGM) with a combined mean 10 Be and 36 Cl age of 22.0 ± 4.9 ka (1 SD; n = 9, 7 outliers). The youngest exposure ages are from moraines that were emplaced during the Younger Dryas with a combined mean 10 Be and 36 Cl age of 12.3 ± 0.9 ka (1 SD; n = 7, no outliers) and are found in cirques at the highest elevations ranging from ∼2900 to 3300 m a.s.l. From moraines predating the Younger Dryas, a large number of young outliers are spread evenly between 6 and 13 ka suggesting a continuing process of exhumation or repositioning of boulders during the early to mid-Holocene. This attests to active seismic processes and possibly intense erosion during this period. [ABSTRACT FROM AUTHOR]

Debris-covered glaciers are glaciers with the largest part of the ablation zone covered by a debris layer. Recent papers showed that debris-covered glaciers are able to support plant and arthropod life, advancing the hypothesis that such landforms could act as warm-stage refugia for cold-adapted species due to their microclimate features and thermal inertia. However, integrated research comparing debris-covered glaciers with surrounding landforms to outline their ecological peculiarities are currently lacking. We analyze some abiotic (glacier surface velocity, ice melting rate and supraglacial debris thickness; ground temperature and humidity; substrate physical and chemical parameters) and biotic features (vascular plant and arthropod communities) of an Alpine debris-covered glacier (Belvedere, Western Alps, Italy), and compare them with those of the surrounding iceless landforms as reference sites (stable slope and iceless moraine). Our data show remarkable differences between stable slopes and unstable landforms as a whole (iceless moraine and supraglacial debris). The iceless moraine and the supraglacial debris show similar substrate features, but different ground temperature (lower on supraglacial debris) and different occurrence of cold-adapted species (more frequent/abundant on supraglacial debris). Such differences could be attributed to the thermal effect of underlying ice. Our data support the hypothesis advanced by previous studies: the thermal contrast with the surrounding landforms and the ability to descend below the climatic treeline give debris-covered glaciers the ecological requirements to be considered potential warm-stage refugia for cold-adapted species. However, our data highlighted that biotic colonization of such landforms could be prevented by some glaciological features, like the mechanical disturbance due to the ordinary ice dynamics (e.g. high glacier surface velocity) and time since the last extraordinary ice dynamic (e.g. surge-type movements). The combined effect of such features is currently preventing colonization by low-dispersal taxa as some cold-adapted ground beetles. [ABSTRACT FROM AUTHOR]

The importance of glaciers for providing runoff is reflected in the extensive glacier measurement record for China. In this paper, we summarized the mass-balance and front-variation data of glaciers in China that have long-term records. Mass balance has been measured for 22 glaciers; length (or front-position) records exist for 96 glaciers. We found that the mean rate of glacial mass balance decreased by −0.015 m w.e. (water equivalent) per year during the period 1959–2015, which was lower than that for glaciers globally (−0.013 m w.e. per year). It was indicated that the rate of glacial melting (mass loss) increased in China, which was higher than that in glaciers worldwide. However, glacial frontal positions varied among mountains in time and space. Glaciers in the Karakoram Mountains mean advanced 379 m during the 1968–2000 period, while glaciers in the Pamir Mountains remained relatively stable from the 1960s through the 2000s, i.e., retreated 28 m. Glaciers in Hengduan Mountains retreated farthest (1250 m maximum) from 1930 to 2005. [ABSTRACT FROM AUTHOR]

Mass balance of a glacier is an accepted measure of how much mass a glacier gains or loses. In theory, it is typically computed by integral functional and empirically, it is approximated by arithmetic mean. However, the variability of such an approach was not studied satisfactory yet. In this paper we provide a dynamical system of mass balance measurements under the constrains of 2nd order model with exponentially decreasing covariance. We also provide locations of optimal measurements, so called designs. We study Ornstein–Uhlenbeck (OU) processes and sheets with linear drifts and introduce K optimal designs in the correlated processes setup. We provide a thorough comparison of equidistant, Latin Hypercube Samples (LHS), and factorial designs for D- and K-optimality as well as the variance. We show differences between these criteria and discuss the role of equidistant designs for the correlated process. In particular, applications to estimation of mass balance of Olivares Alfa and Beta glaciers in Chile is investigated showing that simple application of full raster design and kriging based on inter- and extrapolation of points can lead to increased variance. We also show how the removal of certain measurement points may increase the quality of the melting assessment while decreasing costs. Blow-ups of solutions of dynamical systems underline the empirically observed fact that in a homogenous glaciers around 11 well-positioned stakes suffices for mass balance measurement. [ABSTRACT FROM AUTHOR]

Understanding the role of fjords in modulating the long-term interaction between ice sheets and glaciers with the surrounding ocean requires the investigation of glacigenic landform and sediment archives. In Svalbard, there is a wealth of data from fjords in west Spitsbergen that constrains the glacial history of this sector of the Svalbard-Barents Sea Ice Sheet (SBIS) since the Last Glacial Maximum (LGM), and the nature and timing of subsequent ice retreat. In contrast, however, very little is known about the glacial history of fjords in east Spitsbergen. This paper combines multibeam swath-bathymetry, sub-bottom profiles, lithological data and radiocarbon dates from Lomfjorden, Svalbard, to provide the first insights into the dynamics of tidewater glaciers and associated glacimarine sedimentary processes in a northeast Spitsbergen fjord. At the LGM, a fast-flowing ice stream drained the SBIS through Lomfjorden, serving as a tributary to a south-north flowing ice stream in Hinlopenstretet. Ice advance is recorded by streamlined bedrock, glacial lineations and drumlins. A radiocarbon date of ∼9.7 ka BP from the outer fjord provides a minimum date for retreat of this ice stream, and suggests that Lomfjorden was ice-free earlier than fjords in west Spitsbergen. Ice retreat occurred in a slow and step-wise manner, indicated by the presence of recessional moraines and De Geer moraines. By 4.5 ka BP the local tidewater glaciers had probably retreated inland of their present positions. The limited extent of glacigenic landform assemblages in front of these glaciers implies that any Holocene re-advances were probably restricted. The principal sedimentary processes during deglaciation were suspension settling from meltwater, causing deposition of weakly stratified, bioturbated mud in ice-distal settings at rates of 0.02–0.08 cm a −1 , and gravitational mass flows forming sandy turbidites in ice-proximal areas. Iceberg ploughmarks and ice-rafted debris provide evidence for the presence of large icebergs during deglaciation. Our data suggest an early and extensive deglaciation in east Spitsbergen fjords and show that previous reconstructions of the extent of the SBIS need to be revised as new data emerges from east Spitsbergen. The data confirm that tidewater glaciers from different regions of Spitsbergen behaved differently since the LGM, and that variations in landform-sediment assemblages occur even within geographically adjacent fjords. [ABSTRACT FROM AUTHOR]

Climate models and ongoing monitoring studies predict the remaining glaciers in Africa are predicted to disappear by the middle of the 21st Century. These will likely be the only glaciers present on the continent for some tens of thousands of years, until the next global ice age. This paper considers the implications of the shrinking cryosphere in Africa for the surrounding environment and local communities. Glacier retreat will give rise to significant and irreversible downstream effects on East African mountain landscapes in future decades, including impacts on water resources; slope stability and geohazards; ecosystems and ecosystem services; and human socioeconomic and cultural activities and heritage. This foresight study is the first to discuss future environmental impacts of deglacierization in East Africa, and this is framed around understanding the interconnections that exist between physical and human landscape elements in mountainous regions. A key outcome is the identification of elements of mountain systems that are most sensitive to environmental disturbance as a result of global warming, such as long-term water availability and processes that give rise to geohazards, and highlighting the need for management and mitigation of these varied impacts. • Glaciers in East African mountains are rapidly melting. • These will be the only glaciers present in Africa until the next global ice age. • Glacier retreat will result in significant and irreversible downstream environmental effects. • Most affected will be regional water resources, geohazards, and ecosystem services. • Change in mountain landscapes will impact on socioeconomic and cultural activities. [ABSTRACT FROM AUTHOR]

Patagonia features the most extensive glaciers of the Southern Hemisphere, excluding Antarctica, and a vast inventory of glacial landforms, so it is thought to have played a key role in (paleo)glacier studies since the late 19th century. However, no systematic attempts to characterize the specific research trends and the scientific community focused on Patagonian cryosphere have been conducted so far. To fill this gap, we analyzed the metadata associated to 305 articles compiled from the Web of Science database following a bibliometric approach covering the period between 1976 and 2020. Our results point to an irregular but net increase on the number of contributions on Patagonian (paleo)glaciers. Mass balance analyses based on satellite data of present-day glaciers and the reconstruction of past glacier activity by dating glacial landforms formed during the Last Glacial Termination, were the most addressed topics during the analyzed period. Patagonian (paleo)glacier studies are mostly published in generic Earth Sciences publications, followed by Quaternary and glaciological journals. Most of the studies were led by scientists from the United Kingdom, followed by Chile, Argentina and United States. In terms of collaborations, these studies can be divided into two main clusters, one composed by researchers from United States, Chile and Argentina institutions, and another mostly composed by British researchers. So far, the most prolific authors are nearly equally distributed in nationality, yet gender inclusion and international collaborations are still caveats that must be solved. Even though our query on the Web of Science missed highly influential (so-called) grey literature, such as local scientific journals and technical reports, the reviewed scientific literature unambiguously indicates that Patagonia is a privileged location for (paleo)glaciers studies worldwide and that it will continue offering vast opportunities to tackle critical questions related to global cryosphere and past-to-present climate changes. • Patagonia is a privilege site for studying present and past glacier dynamics and the evolution of climate changes at hemispheric and global scale. • Glacier dynamics during the 20th century and and the Last Glacial Termination are the most common topics addressed in past decades in the WOS. • Patagonian (paleo)glacier studies has contributed to the development or improvement of diverse analytical techniques. • United Kingdom, United States, Chile and Argentina produced the largest number of WOS-listed papers on (paleo)glaciers in past decades. • The related scientific community is fairly heterogeneous. Although, inclusion and international collaboration issues still need to improve. [ABSTRACT FROM AUTHOR]

Much research, especially within the framework of the Fluvial Archives Group, has focused on river response to climate change in mid-latitude non-glaciated areas, but research into the relationships between Quaternary glacial and fluvial dynamics remains sparse. Understanding glacial–fluvial interactions is important because glaciers are able to influence river behaviour significantly, especially during glacial and deglacial periods: (1) when they are located downstream of a pre-existing fluvial system and disrupt its activity, leading to hydrographical, hydrosedimentary and isostatic adjustments, and (2) when they are located upstream, which is a common scenario in mid-latitude mountains that were glaciated during Pleistocene cold periods. In these instances, glaciers are major water and sediment sources. Their role is particularly significant during deglaciation, when meltwater transfer towards the fluvial system is greatly increased while downstream sediment evacuation is influenced by changes to glacial–fluvial connectivity and basin-wide sediment storage. This means that discharge and sediment flux do not always respond simultaneously, which can lead to complex fluvial behaviour involving proglacial erosion and sedimentation and longer-term paraglacial reworking. These processes may vary spatially and temporally according to the position relative to the ice margin (ice-proximal versus ice-distal). With a focus on the catchments of Europe, this paper aims to review our understanding of glacial impacts on riversystem behaviour. We examine the methods used to unravel fluvial response to 'glacial forcing', and propose a synthesis of the behaviour of glacially-fed rivers, opening perspectives for further research. [ABSTRACT FROM AUTHOR]

On Spitsbergen, which is 60% glaciated, talus slopes have frequently developed in interaction with glaciers, which had an influence on the evolution of the internal structure of slopes. This paper presents the results of geophysical surveys (electrical resistivity tomography – ERT and ground-penetrating radar – GPR) of the talus slopes near the Hans Glacier (SW Spitsbergen). The aim of investigations was to compare the talus slopes under the influence of glaciers in two different parts of the area in order to reveal differences in their internal structure. We assumed that different locations of talus slopes can have an influence on the slope structure, showing different stages of evolution of the talus slopes. The maximum thickness of studied slopes ranges from 20 m in a marginal zone of the glacier, to up to 35 m without contact with the glacier. Permafrost begins at a depth of 2–3 m and can develop until bedrock is reached. The internal structure of these talus slopes contains glacial ice, which is covered by a layer of slope material with a thickness from a few to up to 10 m. The buried glacial ice is slowly melting simultaneously with the deglaciation of the area but can remain in the structure of the talus slopes for much longer. Morphogenetic processes, such as avalanches, rockfalls, and debris flows are most visible until the glacial ice is completely melted within the internal structure of the slope. Based on the geophysical and geomorphological data, general models were proposed for the early stages of evolution of talus slopes in valleys under deglaciation. [ABSTRACT FROM AUTHOR]

We report on the AMADEE-15 mission, a 12-day Mars analog field test at the Kaunertal Glacier in Austria. Eleven experiments were conducted by a field crew at the test site under simulated martian surface exploration conditions and coordinated by a Mission Support Center in Innsbruck, Austria. The experiments’ research fields encompassed geology, human factors, astrobiology, robotics, tele-science, exploration, and operations research. A Remote Science Support team analyzed field data in near real time, providing planning input for a flight control team to manage a complex system of field assets in a realistic work flow, including: two advanced space suit simulators; and four robotic and aerial vehicles. Field operations were supported by a dedicated flight planning group, an external control center tele-operating the PULI-rover, and a medical team. A 10-min satellite communication delay and other limitations pertinent to human planetary surface activities were introduced. This paper provides an overview of the geological context and environmental conditions of the test site and the mission architecture, with a focus on the mission's communication infrastructure. We report on the operational workflows and the experiments conducted, as well as a novel approach of measuring mission success through the introduction of general analog mission transferrable performance indicators. [ABSTRACT FROM AUTHOR]

In this paper, satellite image transformations (SIT) for detection and monitoring of the continuous snow covers and glaciers (SCG) were evaluated using Landsat 5 TM (30 m), Landsat 8 OLI (30 m) and RASAT (7.5 m) satellite images at a regional scale. The study was performed in two stages. Firstly, four potential SCG detection indices were produced from the 23rd of August 2013 Landsat 8 image as a Normalized Difference Snow Index (NDSI), a Normalized Difference Snow-Ice Index (NDSII), a Normalized Difference Principle Component Snow Index (NDPCSI) and Tasseled Cap Wetness transformation (WET) as indicators of the SCG. Continuous SCG amount was obtained classifying the August 2013 RASAT satellite image using an object based classification technique as ground truth data. Kappa accuracy co-efficiency of the NDSI, NDSII, NDPCSI and WET were calculated to be 0.74, 0.76, 0.4 and 0.77 respectively. In the second stage, WET SCG maps were produced from August 1984, 2000 and 2015 Landsat images. Changes in the two time periods (1984–2000 and 2000–2015) showed that total SCG loss was 247 ha from August 1984 to August 2015. Almost 47% of the SCG loss recorded in the region in 31 years. The highest loss was observed in the 1st period (198 ha). However, only 49 ha SCG loss was detected in the 2nd period although the 5 year mean temperature changes were found to be similar both in the 1st and 2nd period. Because the most sensitive SCG areas (regions that are located at a lower slope and thus receive more sunlight) had melted in the 1st period. Finally, physical variables were more significant than temperature in the 2nd period for the stability of SCG in the study area. [ABSTRACT FROM AUTHOR]

Glacier reconstructions are widely used in palaeoclimatic studies and this paper presents a new semi-automated method for generating glacier reconstructions: GlaRe, is a toolbox coded in Python and operating in ArcGIS. This toolbox provides tools to generate the ice thickness from the bed topography along a palaeoglacier flowline applying the standard flow law for ice, and generates the 3D surface of the palaeoglacier using multiple interpolation methods. The toolbox performance has been evaluated using two extant glaciers, an icefield and a cirque/valley glacier from which the subglacial topography is known, using the basic reconstruction routine in GlaRe. Results in terms of ice surface, ice extent and equilibrium line altitude show excellent agreement that confirms the robustness of this procedure in the reconstruction of palaeoglaciers from glacial landforms such as frontal moraines. [ABSTRACT FROM AUTHOR]