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Dań Zhùr (Donjek) Glacier is a surge-type glacier that undergoes cyclical periods of rapid advance over ∼1–2 years, followed by retreat for ∼10 years. Since the 1990s, the advances have caused the formation of ice-dammed Dań Zhùr Lake, which has filled and drained in summers following a surge event. Here, we report how these drainages initially occur through a subglacial channel under the glacier terminus, which then typically closes the following winter, enabling another lake to form and drain the next summer. However, our remote sensing and field observations indicate that after several drainage events, a subaerial ice canyon is formed through the glacier terminus, which prevents another lake from forming until after the glacier surges again. We predict that the next surge of Dań Zhùr Glacier will occur around the mid-2020s, causing the formation of a larger Dań Zhùr Lake during the following quiescent phase because, despite periodic advances, a long-term trend of glacier recession is exposing a larger basin for the lake to form in. However, each subsequent surge is causing less terminus advance than the previous one, until ultimately the surges will be insufficient to dam Dań Zhùr Chù’ (Donjek River), and lakes will cease to form.

Glacier surges can create ice-dammed lakes when the advancing terminus blocks drainage. Such lakes are inherently unstable and can drain abruptly as glacial lake outburst floods (GLOFs), presenting a hazard to downstream populations and infrastructure in high mountain environments. We present satellite image analysis of the evolution of an ice-dammed lake formed by the 2018–20 surge of Shisper Glacier, western Karakoram. Our analysis identifies six phases of lake evolution. A large lake of up to 33.7 ± 9% million m3 formed in 2018–19, 2019–20, 2020–21 and 2021–22. In each case, the lake began to fill late in the year, reached a maximum size in May, and had completely drained between May and July, typically over 1–2 days. This analysis provides further evidence that GLOF hazards associated with lakes dammed by glacier surges can persist for several years after surge termination.

Lake-terminating glaciers have some peculiar behaviors compared to land-terminating glaciers, but in-depth observation is still limited regarding their formation, which is crucial for understanding the glacier–lake interaction. Here, the long-term evolutions of Tanymas Lake and the Fedchenko Glacier were investigated based on Landsat images, Google Earth imagery, KH-9 images, glacier surface elevation and velocity change datasets, and meteorological records. The results indicate that Tanymas Lake is both an ice-contact proglacial lake and an ice-dammed lake. It covered an area of 1.10 km2 in September 2022, and it is one of the largest glacial lakes in Pamir and even in HMA. The initial basin of Tanymas Lake is a moraine depression in Tanymas Pass, and the blocked dam is the Tanymas-5 Glacier and its terminal moraine. Tanymas Lake was in an embryonic stage before August 2005, in a formation and expansion stage from August 2005 to September 2018, and in a new expansion stage after September 2018. In this process, the Tanymas terminus of the Fedchenko Glacier also transformed from a land terminus to a partial lake terminus, and then to a complete lake terminus. The formation of Tanymas Lake is associated with the accumulation of glacial meltwater and the blockage of drainage, while the slow expansion of Tanymas Lake is related to the cold climate and slight glacier mass loss of Central Pamir. In the coming decades, with the accelerated mass loss of the Tanymas terminus of the Fedchenko Glacier, the area, depth, and water storage of Tanymas Lake will continue to increase, accompanied by the growing GLOF risk. [ABSTRACT FROM AUTHOR]

The Siljan region hosts Europe's largest impact structure. The high‐relief landscape, with a central granite dome bordered by lake basins, contains an array of glacial and shore‐level landforms. We investigated its deglaciation history by mapping and analysing landforms on high resolution LiDAR (light detection and ranging)‐based digital surface models coupled with well‐dated sediment successions from peat and lake sediment cores. The granite dome and bordering areas are characterized by streamlined terrain and ribbed moraine with a streamlined overprint. These suggest an ice‐flow direction from north‐northwest (NNW) with wet‐based thermal conditions prior to deglaciation. During its retreat, the ice sheet was split into thinner plateau ice and thicker basin ice. Sets of low‐gradient glaciofluvial erosion channels suggest intense ice‐lateral meltwater drainage across gradually ice‐freed slopes, while 'down‐the‐slope' erosion channels and eskers show meltwater drainage from stagnated plateau ice. Thick basin ice receded with a subaqueous margin across the deep Siljan–Orsasjön Basin c. 10,700–10,500 cal. bp. During ice recession the ingression of the Baltic Ancylus Lake led to diachronous formation of highest shoreline marks, from ~207 m in the south to ~220 m above sea level (a.s.l.) in the north. Differential uplift resulted in shallowing of the water body, which led to the isolation of the Siljan–Orsasjön Basin from the Baltic Basin at c. 9800 cal. bp. The post‐isolation water body – the 'Ancient Lake Siljan' – was drained through the ancient Åkerö Channel with a water level at 168–169 m a.s.l. during c. 1000 years. A later rerouting of the outlet to the present course was initiated at c. 8800 cal. bp, which led to a lake‐level lowering of 6–7 m to today's level of Lake Siljan (~162 m a.s.l.). This study shows the strength of an integrated methodological approach for deciphering the evolution of a complex landscape, combining highly resolved geomorphological analysis with well‐dated sediment successions. [ABSTRACT FROM AUTHOR]

A proglacial lake system formed during the Late Valdai (Weichselian) Ice Sheet recession on the East European Plain. Poor knowledge about chronology, levels and the drainage pathways of ice‐dammed lakes does not allow us to fully evaluate their palaeogeographic significance. This study focuses on the Izborsko‐Malskaya Valley where fingerprints of a glaciolacustrine environment were found. Based on litho‐, biostratigraphic and geochronological data, it is estimated that the proglacial lake in the Izborsko‐Malskaya Valley existed from ~14.3 ka cal. BP (the Vashinogorskaya Valley from ~14.9 ka (optically stimulated luminescence)) to 13.2 ka cal. BP. The maximum level was ~72 m a.s.l. (above sea level) and the minimum was ~53 m a.s.l. Sedimentation proceeded mostly in deepwater conditions. The ice‐dammed lake in the Izborsko‐Malskaya and nearest valleys could have been part of a huge lake on the Pskov lowland which formed after ~15.7 ka cal. BP. The lake level dropped rapidly when the proglacial Lake Pskovsko‐Chudskoe (Peipsi) connected with the Baltic Ice Lake. A lacustrine regime was preserved only in the southern portion of the Izborsko‐Malskaya Valley after drainage and still exists in the modern lakes. The presented approaches to the ice‐dammed lake reconstruction could be useful for the verification of other lakes which existed on the East European Plain. [ABSTRACT FROM AUTHOR]

Hydro‐acoustic and seismic data and 2‐ to 16‐m‐long sediment cores from the central area of Lake Taymyr (Taymyr Peninsula, central Russian Arctic) were investigated to reconstruct its sedimentation history. Granulometric, chronological, geochemical and biological data from the sediment cores reveal two lowstands and two highstands of the lake level, which is today located ca. 5 m above sea level during summer. Our study confirms the presence of an ice sheet blocking the drainage of Lake Taymyr during the latest Weichselian. Although chronological control of the sediment cores does not allow us to unambiguously constrain the time frame for each of the lake stages, the proposed timing of events is in good agreement with regional terrestrial archives as well as marine signals on the Kara Sea Shelf. Overall, the data show that the evolution of Lake Taymyr involved a complex interplay of regional climatic, glacial and sea‐level changes. [ABSTRACT FROM AUTHOR]

The existence of supraglacial lakes influences debris-covered glaciers in two ways. The absorption of solar radiation in the water leads to a higher ice ablation, and water draining through the glacier to its bed leads to a higher velocity. Rising air temperatures and changes in precipitation patterns provoke an increase in the supraglacial lakes in number and total area. However, the seasonal evolution of supraglacial lakes and thus their potential for influencing mass balance and ice dynamics have not yet been sufficiently analyzed. We present a summertime series of supraglacial lake evolution on Baltoro Glacier in the Karakoram from 2016 to 2020. The dense time series is enabled by a multi-sensor and multi-temporal approach based on optical (Sentinel-2 and PlanetScope) and Synthetic Aperture Radar (SAR; Sentinel-1 and TerraSAR-X) remote sensing data. The mapping of the seasonal lake evolution uses a semi-automatic approach, which includes a random forest classifier applied separately to each sensor. A combination of linear regression and the Hausdorff distance is used to harmonize between SAR- and optical-derived lake areas, producing consistent and internally robust time series dynamics. Seasonal variations in the lake area are linked with the Standardized Precipitation Index (SPI) and Standardized Temperature Index (STI) based on air temperature and precipitation data derived from the climate reanalysis dataset ERA5-Land. The largest aggregated lake area was found in 2018 with 5.783 km2, followed by 2019 with 4.703 km2, and 2020 with 4.606 km2. The years 2016 and 2017 showed the smallest areas with 3.606 and 3.653 km2, respectively. Our data suggest that warmer spring seasons (April–May) with higher precipitation rates lead to increased formation of supraglacial lakes. The time series decomposition shows a linear increase in the lake area of 11.12 ± 9.57% per year. Although the five-year observation period is too short to derive a significant trend, the tendency for a possible increase in the supraglacial lake area is in line with the pronounced positive anomalies of the SPI and STI during the observation period.

Shishper lake is an ice-dammed lake in northern Pakistan that has drained twice within one (1) year. The parameters evaluated in this paper are the lake's area, volume, peak discharge, and its outburst events using various satellite images from November 2018 to June 2020. Based on satellite imagery and empirical approaches, the lake formed in November 2018 and reached a maximum of 0.34 km2 till its first breach that occurred on 22 June 2019. Since June 2019, the lake drained till September 2019. After that, the flow was blocked again, and the lake expanded to an area of 0.27 km2 till its second outburst event that happened on May 29, 2020. Eight cross-sectional profiles of Hassanabad ravine are generated based on peak discharge in the lake's rapid outburst. The results indicate that, the peak discharge for both 2019 and 2020 was more than 4500 m3 s−1. Delineation of downstream Hassanabad ravine shows that more than 1000 buildings and 2000+ population is prone to flood. However, the lake drain twice steadily, but it has a high potential to cause severe damages if it bursts abruptly. [ABSTRACT FROM AUTHOR]

This study shows the occurrence of numerous iceberg imprints on the bottom of former ice-dammed lakes in Härjedalen, west-central Sweden. Discussion of the genesis of the so-called "impact crater" known as the Tor structure at Torbygget, which is located in this area, motivated an examination of the area using high-resolution digital elevation models. Previous investigations have suggested that this crater was created by a meteorite impact about 2000 years ago, forming a semi-round depression. The results of our investigation clearly indicate that the feature was formed by a grounding iceberg, scouring the bed of an ice-dammed lake during deglaciation about 11 000-10 000 cal. BP. Geomorphic evidence of an ice-dammed lake (multiple and abundant well-developed shorelines) are consistent with earlier mapping efforts in the area. Furthermore, an abundance of geomorphological traces of iceberg activity is found within the paleo-ice-dammed lake basins. Based on this we suggest that the depression at Torbygget is not an impact crater but formed by a grounded iceberg. [ABSTRACT FROM AUTHOR]

In the Middle Gauja Lowland, northeast Latvia, dunes are distributed over a vast glaciolacustrine plain that formed during the retreat of the Fennoscandian ice sheet. Such a direct contact between aeolian and glaciolacustrine sediments can be used to infer depositional settings and decipher to what extent these sediments bear an aeolian component. Our proxies, although preliminary, reveal a limited range of variation in grain-size parameters, a significant presence of quartz grains with silica precipitation and matt-surface grains of various rounding degrees and massive structure combined with horizontal lamination. These are indicative of periglacial-aeolian depositional conditions in the foreland of the Linkuva ice-marginal zone. Sedimentary characteristics do not match a single luminescence date of 9.2±0.6 ka, which significantly postdates the minimum age of the Linkuva ice-marginal zone with 10Be ages between 15.4 and 12.0 ka. Whether deposition started directly after drainage of the Middle Gauja ice-dammed lake or if there is a gap of 2.8–6.2 ka is a matter of debate; only future studies at higher OSL resolution could resolve this.

Recent reconstructions suggest that the British-Irish and Fennoscandian ice sheets coalesced and covered the central and northern North Sea from ca. 26 cal. ka BP and until ca. 19 cal. ka BP. At ca. 19 cal. ka BP the Norwegian Channel Ice Stream started to retreat and the ice sheets broke apart at ca. 18.7 cal. ka BP. This led to a drainage of an ice-dammed lake in the southern North Sea northwards via the Norwegian Channel into the SE Nordic Seas. In this paper we combine information from high resolution TOPAS profiles, bathymetric records and shallow borings to study the ice-dammed lake outburst, a common deglaciation process but which rarely has been evidenced in such a detail from the marine realm. A 12 m deep and 3 km wide incision at the northeastern part of the Dogger Bank is suggested to represent the point where the ice-dammed lake breached. The glacial lake outburst flood, which had an estimated peak discharge of 9.8 × 10 4 –2.9 × 10 5 m 3 /s and lasted for about 5–15 months, flowed between the withdrawing British-Irish and Fennoscandian ice sheets following the crest of the Ling Bank northwards. Along this path, about 300 km downstream of the break-through point, an up to 10 m thick sediment package with a prograding-aggrading sedimentation pattern, typical for ice-dammed lake outburst deposits, has been deposited. This sediment package was deposited in a high-energy environment, immediately following extensive erosion of the underlying till unit of Last Glacial Maximum age. An oxygen isotope anomaly and an associated ultra-rapidly deposited meltwater plume on the Norwegian continental margin, dated to ca. 18.7 cal. ka BP, also witness this lake outburst. The ice-dammed lake outburst flood occurred when evidence suggest a sea level at least 110 m lower than at present in the region. As the sea level rose, following the melting of the Last Glacial Maximum ice sheet, the Ling Bank Delta developed on top the outburst deposits. The delta, indicating a sea level close to 80 m below present, has an extent of 80 km and up to 12 m deep fluvial channels are associated with the topset beds. This fluvial environment may have lasted until the end of the Younger Dryas time period when the Ling Bank was submerged and attained its present water depth. [ABSTRACT FROM AUTHOR]

Combined geomorphic features, stratigraphic characteristics and sedimentologic interpretation, coupled with optically stimulated luminescence (OSL) dates, of a glacio-fluvio-lacustrine sequence (Linás de Broto, northern Spain) provide new information to understand the palaeoenvironmental significance of dynamics of glacier systems in the south-central Pyrenees during the Last Glacial Cycle (≈130 ka to 14 ka). The Linás de Broto depositional system consisted of a proglacial lake fed primarily by meltwater streams emanating from the small Sorrosal glacier and dammed by a lateral moraine of the Ara trunk glacier. The resulting glacio-fluvio-lacustrine sequence, around 55 m thick, is divided into five lithological units consisting of braided fluvial (gravel deposits), lake margin (gravel and sand deltaic deposits) and distal lake (silt and clay laminites) facies associations. Evolution of the depositional environment reflects three phases of progradation of a high-energy braided fluvial system separated by two phases of rapid expansion of the lake. Fluvial progradation occurred during short periods of ice melting. Lake expansion concurred with ice-dam growth of the trunk glacier. The first lake expansion occurred over a time range between 55 ± 9 ka and 49 ± 11 ka, and is consistent with the age of the Viu lateral moraine (49 ± 8 ka), which marks the maximum areal extent of the Ara glacier during the Last Glacial Cycle. These dates confirm that the maximum areal extent of the glacier occurred during Marine Isotope Stages 4 and 3 in the south-central Pyrenees, thus before the Last Glacial Maximum. The evolution of the Linás de Broto depositional system during this maximum glacier extent was modulated by climate oscillations in the northern Iberian Peninsula, probably related to latitudinal shifts of the atmospheric circulation in the southern North-Atlantic Ocean, and variations in summer insolation intensity. [ABSTRACT FROM AUTHOR]

An accumulation of glacial sediments is located near Písečná village in the depression between the Sokol Ridge and Zlaté Hory Highlands NNE of Jeseník town (Eastern Sudetes). The accumulation lies at the lateral side of the mountain valley of the Bělá River and fills a preglacial palaeovalley of this river. Research combining facies analysis of outcrops, ground penetrating radar survey, interpretation drilling survey, and modelling of the preglacial relief was undertaken at the site. According to the results obtained, the upper part of the sedimentary accumulation represents a coarse-grained terminoglacial glaciofluvial delta of the Gilbert type. The development of the accumulation has dominantly been driven by the preglacial morphology. Facies typical for foresets of coarse-grained deltas represented mainly by high-density flows, cohesionless debris flows, debris falls and less common low-density flows were found in the outcrops. The delta near Písečná prograded into a lake dammed by the ice-sheet front in the north. The lake was bounded by the slopes of Sokol Ridge, Zlaté Hory Highlands and Góry Parkowe on other sides. The lake level reached an altitude of up to 430 m a.s.l., as the coarse-grained delta plain base lies at this level. [ABSTRACT FROM AUTHOR]

The thinning and final decay of the Scandinavian Ice Sheet in the Gudbrandsdalen area in central southern Norway is described, based on (1) cosmogenic 10Be surface exposure dating of 25 glacially transported boulders, (2) radiocarbon dating of plant remains in the basal strata in four lakes and (3) mapping of large ice-dammed lakes that formed at different elevations and at different times during the last deglacation. We complement the new chronology with previously published 10Be-ages from the same region. The dated samples are spread from mountain summits 1800 m a.s.l. to the valley floor at 250 m a.s.l. Our results suggest that the ice sheet surface remained well above 1800 m a.s.l. in northern Gudbrandsdalen throughout the Younger Dryas. During the Early Holocene the ice sheet thinned rapidly, at rates estimated to 1.7–5.8 m yr−1. The final phase of deglaciation involved formation of large ice-dammed lakes, most notably the Store Dølasjø which was formed after 10.4 ka BP and finally drained around 10.0 ka BP. The ice-marginal landforms that characterize the mountain region of northern Gudbrandsdalen, i.e., moraine ridges, lateral meltwater channels, as well as deposits and shorelines from ice-dammed lakes, thus collectively originate from a period of rapid ice sheet downwasting over ca. 1600 years. • Three independent methods used to reconstruct deglaciation in southern Norway. • Ice-dammed lakes, 10Be-dating of boulders and radiocarbon dated lake records. • Thinning rates for the Scandinavian Ice Sheet based on empirical data. • New reconstruction and dating of the Store Dølasjø ice-dammed lake. • Important constraints for ice sheet models and eustatic sea level budgets. [ABSTRACT FROM AUTHOR]

A comprehensive palaeogeographic reconstruction of ice sheets and related proglacial lake systems for the older Saalian glaciation in northern central Europe is presented, which is based on the integration of palaeo-ice flow data, till provenance, facies analysis, geomorphology and new luminescence ages of ice-marginal deposits. Three major ice advances with different ice-advance directions and source areas are indicated by palaeo-ice flow directions and till provenance. The first ice advance was characterised by a southwards directed ice flow and a dominance of clasts derived from southern Sweden. The second ice advance was initially characterised by an ice flow towards the southwest. Clasts are mainly derived from southern and central Sweden. The latest stage in the study area (third ice advance) was characterised by ice streaming (Hondsrug ice stream) in the west and a re-advance in the east. Clasts of this stage are mainly derived from eastern Fennoscandia. Numerical ages for the first ice advance are sparse, but may indicate a correlation with MIS 8 or early MIS 6. New pIRIR 290 luminescence ages of ice-marginal deposits attributed to the second ice advance range from 175 ± 10 to 156 ± 24 ka and correlate with MIS 6. The ice sheets repeatedly blocked the main river-drainage pathways and led to the formation of extensive ice-dammed lakes. The formation of proglacial lakes was mainly controlled by ice-damming of river valleys and major bedrock spillways; therefore the lake levels and extends were very similar throughout the repeated ice advances. During deglaciation the lakes commonly increased in size and eventually drained successively towards the west and northwest into the Lower Rhine Embayment and the North Sea. Catastrophic lake-drainage events occurred when large overspill channels were suddenly opened. Ice-streaming at the end of the older Saalian glaciation was probably triggered by major lake-drainage events. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar (SAR) satellite imagery was used to reconstruct the change in limnological conditions adjacent to an Arctic ice shelf by examining the backscatter values of coastal ice in mid-winter scenes. High SAR backscatter values (>− 6 dB) suggest that an ice-dammed lake was present adjacent to the south coast of Petersen Bay from 1992 until 2005. Following a large calving event of the adjacent Petersen Ice Shelf (− 8.07 km 2 ) in August 2005, the lake drained through a region where the ice shelf had separated from the coastline. This loss of freshwater and replacement of lake ice with sea ice along the southern coast of Petersen Bay were confirmed from analyses of ice core samples and conductivity–temperature–depth (CTD) profiles. The exception to this pattern was one distinct area where terrestrial streams entered the edge of Petersen Bay and freshwater continued to collect from 2006 to 2008. However, this ephemeral area of freshwater has not reformed since 2009 due to the persistence of open water events in Petersen Bay (observed in optical satellite imagery), which likely facilitated mixing of freshwater with sea water. Based on the continued break-ups of Petersen Ice Shelf and the frequency of open water events, it is unlikely that this ice-dammed lake will reform. The results of this study underscore the utility of SAR for reconstructing past hydrographic conditions in the water column below. [ABSTRACT FROM AUTHOR]

We investigated drainage events from a glacier-dammed lake on Bear Glacier, Alaska, and associated outburst floods and hazards. The glacier-dammed lake, which we call Ice Lake, is 17.5km up-glacier from Bear Glacier's terminus at Bear Glacier Lake. We combine field observations and remote sensing to examine temporal changes in the size of Ice Lake, the frequency and timing of its drainage, and down-glacier propagation of its outburst floods. We found that in recent years, Ice Lake has likely drained every year or two, in late summer or fall (August-October), with outbursts generally following the damming of sufficient water to create a lake area of between 0.35 and 0.5km². Ice Lake has migrated downvalley to the south since the 1990s, likely as a result of thinning of the glacier that dams it. In situ measurements of a drainage event in October 2010 showed that Ice Lake drained over a period of days, which manifested at Bear Glacier Lake as a gradual, multiday increase and then decrease in water levels. Glacial lake outburst flooding at Bear Glacier creates risks for sea kayakers in Bear Glacier Lake and may be relevant to understanding the effects of climate warming on glacier-dammed and proglacial lakes. [ABSTRACT FROM AUTHOR]

During the last decades many studies were concentrated on the North Lithuanian ice marginal ridge of the Last Glaciation (Late Nemunas, Late Weichselian). The North Lithuanian ice marginal ridge or so-called Linkuva ridge was formed by Žiemgala Ice Lobe that advanced at the end of the glaciation through the Gulf of Riga. This ridge is considered as a boundary of glacier limit during the North Lithuanian recessional phase of the Late Nemunas Baltija stage. Linkuva ridge is stretching about 130 km as a bow-shaped ridge and is marking the boundary of an active ice lobe. The thickness of Quaternary deposits is 10-12 meters on the average but varies from 1.0 to 39.0 meters: the thinnest Quaternary cover is characteristic for river valleys, whereas the thickest one is related with the highest altitudes of the present topography or with rare palaeoincisions of the sub-Quaternary surface. Pleistocene strata are subdivided to three till complexes in some places separated by inter-till sediments. [ABSTRACT FROM AUTHOR]

Abstract: The freshwater budget of the Arctic Ocean is a key component governing the deep water formation in the North Atlantic and the global climate system. We analyzed the isotopic composition of neodymium (ε Nd) in authigenic phases of marine sediments on the Mendeleev Ridge in the western Arctic Ocean spanning an estimated time interval from present to about 75ka BP. This continuous record was used to reconstruct the ε Nd of the polar deep water (PDW) and changes in freshwater sources to the PDW through time. Three deviations in ε Nd from a long term average of −10.2 were identified at estimated 46–51, 35–39 and 13–21ka BP. The estimated 46–51ka BP event can be traced to bursting of ice-dammed lakes accompanying the collapse of the Barents–Kara Ice Sheet, which would have released radiogenic Nd to the eastern Arctic Ocean. The cyclonic surface circulation in the eastern Arctic Ocean must have been stronger than at present for the event to be recorded on the Mendeleev Ridge. For the 35–39 and 13–21ka BP events, it is likely that the Laurentide Ice Sheet (LIS) supplied the unradiogenic freshwater. The configuration of the anticyclonic circulation in the western Arctic was probably similar to today or expanded eastward. Our simple mass balance calculations suggest that large amounts of freshwater were released but due to significant deep water formation within the Arctic Ocean, the effect on the formation of NADW was probably minor. [Copyright &y& Elsevier]

Abstract: The pattern of Greenland Ice Sheet margin change during the 20th century is variable. Large-scale retreat of marine-outlet glaciers contrasts with the often-negligible retreat observed along land-terminating margins of the ice sheet. We reconstruct a chronology of ice-margin change for two land-terminating ice margins in western Greenland using radiocarbon and 10Be exposure dating. Our results indicate that two land-terminating lobes attained their maximum late Holocene position in the late 20th century. This contrasts with the nearby marine-terminating Jakobshavn Isbræ, which achieved a maximum late Holocene position during the Little Ice Age, and has since retreated ca 40 km. In addition, we survey ice-margin change across western Greenland, utilizing satellite imagery. We find that many land-terminating sectors of the ice sheet, in addition to our study area, may have attained their maximum late Holocene extent during the 20th century. This suggests a lagged ice-margin response to prior cooling, such as the Little Ice Age, which would imply significant retreat of land-terminating sections of the Greenland Ice Sheet in response to 20th and 21st century warming may be yet to come. [Copyright &y& Elsevier]

Abstract: A prominent lake formed when glaciers descending from the Kodar Range blocked the River Vitim in central Transbaikalia, Siberia. Glacial Lake Vitim, evidenced by palaeoshorelines and deltas, covered 23,500km2 and held a volume of ~3000km3. We infer that a large canyon in the area of the postulated ice dam served as a spillway during an outburst flood that drained through the rivers Vitim and Lena into the Arctic Ocean. The inferred outburst flood, of a magnitude comparable to the largest known floods on Earth, possibly explains a freshwater spike at ~13calka BP inferred from Arctic Ocean sediments. [Copyright &y& Elsevier]

The varved sediment record from glacially-fed Lake Tuborg, Ellesmere Island, Nunavut, shows that only three large jökulhlaups have occurred there in the last millennium: 2003, 1993, and 1960. Detailed analyses of sediment microstructure and particle size, combined with in-situ hydrometeorological and limnological process studies, allowed jökulhlaup facies identification and discrimination from deposits from other processes. Deposits from large jökulhlaups are anomalously thick, typically lack internal structure, have sharp bases, and fine upwards. The ice-dammed lake above Lake Tuborg (the source of the jökulhlaups) likely changed its drainage style in 1960, from ice-dam overtopping to ice-dam flotation and glacial tunnel enlargement by melt widening, which allowed the lake to drain completely and catastrophically. Complete drainage of ice-dammed lakes by ice-dam flotation is rare in the region is due to the pervasiveness of cold-based ice. Twentieth century warming is likely responsible for some combination of dam thinning, lake expansion and deepening, and changing the thermal regime at the base of the dam. Anomalously thick individual varves were periodically deposited beginning in the nineteenth century, and their thickness increased with time. This likely reflects a combination of increased ice dam overtopping, subaqueous slope failures, sediment availability and rising air temperature. The varve record presented here significantly correlates with a previous, shorter record from Lake Tuborg. However, generally weak correlations are found between the new varve time series, regional records of air temperature, and glacial melt from ice cores on the Agassiz Ice Cap. It is hypothesized that on short timescales, sedimentation at the coring location reflects a complex and varying integration of multiple hydroclimatic, geomorphic and limnologic influences. [ABSTRACT FROM AUTHOR]

Abstract: Sedimentary exposures in moraines in a Scottish Highland valley (Glen Chaorach), reveal stacked sequences of bedded and laminated silt, sand and gravel, interspersed or capped with diamicton units. In four examples, faults and folds indicate deformation by glaciotectonism and syndepositional loading. We propose that these sediments were laid down in an ice-dammed lake, close to the last ice margin to occupy this glen. Individual units within cross-valley De Geer moraine ridges are interpreted by comparison with examples from similar environments elsewhere: stratified diamictons containing laminated or bedded lenses are interpreted as subaqueous ice-marginal debris-flow deposits; massive fine-grained deposits as hyperconcentrated flow deposits, and massive gravel units as high-density debris-flow deposits. Using an allostratigraphic approach we argue that glaciotectonically deformed coarsening-upward sand and gravel sequences that culminate in deposition of subglacial diamicton represent glacier advances into the ice-marginal lake, whereas undisturbed cross-bedded sand and gravel reflects channel or fan deposits laid down during glacier retreat. A flat terrace of bedded sand and gravel at the northern end of Glen Chaorach is interpreted as subaerial glaciofluvial outwash. On the basis of these inferences we propose the following three stage deglacial event chronology for Glen Chaorach. During glacier recession, ice separation and intra-lobe ponding first led to subaquaeous deposition of sorted and unsorted facies. Subsequent glacier stabilisation and ice-marginal oscillation produced glaciotectonic structures in the ice-marginal sediment pile and formed De Geer moraines. Finally, drainage of the ice-dammed lake allowed a subaerial ice-marginal drainage system to become established. Throughout deglaciation, deposition within the lake was characterized by abrupt changes in grain size and in the architecture of individual sediment bodies, reflecting changing delivery paths and sediment supply, and by dynamic margin oscillations typical of water-terminating glaciers. [Copyright &y& Elsevier]

Jökulhlaups from lakes dammed by Tulsequah Glacier in northwestern British Columbia have occurred regularly since the early twentieth century. The floods commenced after decades of downwasting and retreat of the glacier from its Holocene maximum position, which it achieved in the nineteenth century. Hydrometric data and other records are used to reconstruct the times and peak discharges of floods from two glacier-dammed lakes. Tulsequah Lake formed in the early 1900s when a tributary glacier separated from Tulsequah Glacier, creating an ice-free embayment between the two. The lake grew rapidly in surface area and volume in the first half of the twentieth century, but later, with continued glacier retreat, it decreased in size. The first jökulhlaups from Tulsequah Lake were the largest. Peak and total discharges decreased as the lake became smaller. Today, Tulsequah Lake is small, and it will disappear completely if Tulsequah Glacier retreats any further. A second lake (Lake No Lake), however, has formed and grown in size as Tulsequah Lake has diminished. Lake No Lake developed from a subglacial water body in a tributary valley, 7 km upglacier from Tulsequah Lake. Like Tulsequah Lake, Lake No Lake rapidly grew in area and volume during its youth, and in the 1970s it began to generate its own jökulhlaups. Lake No Lake appears to be following the same evolutionary path as Tulsequah Lake – its volume is now decreasing due to downwasting of Tulsequah Glacier, and its jökulhlaups are beginning to diminish. As Tulsequah Glacier continues to shrink in response to climatic warming, additional glacier-dammed lakes may form, renewing the cycle of outburst flood activity. Such behaviour can be expected in other high mountains because most alpine glaciers are retreating in response to global warming. [ABSTRACT FROM AUTHOR]

Abstract: Over the past few years there has been an increase in understanding of glacier-impounded or ‘ice-dammed’ lake behaviour. The spectacular jö kulhlaup (catastrophic flood) from Gr'msvötn, Iceland in November 1996 has both raised the profile of such events and emphasized the need for awareness of the processes involved. This review summarizes the extent of current knowledge of ice-dammed lakes, highlighting key developments and outlining areas of study still subject to difficulties. Controls on ice-dammed lake formation and persistence are identified, and cycles of jökulhlaup activity are related to glacier fluctuations. Ice-dammed lake drainage trigger mechanisms are reviewed and recent progress in the understanding of such mechanisms is emphasized. Controls on jökulhlaup routing and the development and character of jökulhlaup conduits are discussed and recent advances in jökulhlaup prediction, hydrograph modelling and peak discharge estimation are assessed. A process-based schematic model, drawing on published research, links ice-dammed lake occurrence and drainage to jökulhlaup characteristics. It is demonstrated that ice-dammed lake and ice-dam characteristics ultimately control seven key jökulhlaup attributes which determine the potential impact of jökulhlaups on both landscape and human activity in glaciated regions. [ABSTRACT FROM AUTHOR]

Unlike glaciers in other parts of the world, Karakoram glaciers seem to be stable or gaining in mass in response to global climate change, a phenomenon known as 'the Karakoram anomaly'. Many of the glaciers experience irregular, frequent, and sudden advances (surges) that pose an increasing threat of ice dam lake formation and subsequent outburst flooding throughout the region. In this study, we document 179 glacial lake outburst floods (GLOFs) that occurred from 1533 to 2020 in five major valleys. Sixty-four of the events took place after 1970, and 37 of these had remote sensing imagery that covered the GLOF formation to breaching sequence. Thirty-six glaciers were associated with GLOFS due to ice-front advance building ice barriers in rivers. The Kayger and Khurdopin glaciers are the most hazardous examples, being responsible for 31.8% of major GLOFs in the entire Karakoram. Using a cross-correlation feature-tracking technique on remote sensing imagery, we analyzed ten surge glaciers and documented six surge events from 1990 to 2019. Results show periodic surge cycles for the Khurdopin, Kyager, Shishper, and Chilinji glaciers of c. 15–20 years, with a surge velocity in the mid-2010s higher than that of the late 1990s for all studied glaciers. The higher velocity of a glacier increases the risk of flooding downstream of the terminus because the transfer of a huge ice mass towards the terminus during the surge is a key factor for formation and reformation of series of ice-dammed lakes, thus determining the magnitude and frequency of outburst flood events. The response of Karakorum glaciers to global warming and climate forcing, comprising a continuum of glacier mass gain, ice thinning and ice advance, has resulted in lake formation and ice dam failures. We predict the frequency of GLOFs will increase in the future. These findings support the increasing anomalous behavior of glaciers in the Karakoram region. To synthesize the detailed observations, a conceptual model is presented of ice-dammed lake formation and GLOF initiation in response to glacier surging. [ABSTRACT FROM AUTHOR]

This study analysed the actively surging Shisper Glacier in the Karakoram region of Pakistan using earth observation data from Landsat 8 OLI and Planet images. Changes in the surface glacier velocity, supraglacial moraines and debris cover were assessed using Landsat 8 data at monthly time-steps from January 2018 to May 2019. High resolution data from Planet Labs was used to precisely detect the snout advance and ice-dammed lake expansion. Downstream cross-section profiles of the valley were generated using a moderate resolution digital elevation model to assess the inundation in the event of rapid ice-dammed lake drainage. Correlation Image Analysis Software working on the principle of normalized cross-correlation was used to generate time series monthly surface velocity profiles for Shisper Glacier. Manual digitization at 1:30000 scale was used to delineate supraglacial moraines and supraglacial debris cover. The glacier surface velocity profiles indicate that the ablation zone of the glacier continues to be in an active surge phase resulting in advance of the snout and expansion of the ice-dammed lake. Surface glacier velocities are as high as 48 m d−1. Between 18 December 2018 and 8 May 2019, the glacier snout advanced at ~6 m d−1 with a total overall advance of 860 m. The lake formed due to damming of an outflow stream from Mochowar Glacier expanded to its maximum area (29.69 ha) in May 2019 before drainage started on 23 June 2019. Our estimates indicate that the peak discharge in case of rapid drainage could vary between 5033 m3 s−1 and 6167 m3 s−1 and potentially affect infrastructure downstream. • Remote sensing methods reveal monthly changes in the velocity of Shisper Glacier. • Glacier surge impacted the distribution of supraglacial debris cover. • The snout of the glacier advanced by 1047 m (February 2018–September 2019). • Ice-dammed lake drained steadily damaging a part of Karakoram highway. [ABSTRACT FROM AUTHOR]

The very largest glacier outburst floods have been termed 'megafloods' given their volume and peak discharge. That definition might be revised because those floods have become understood due to their distinctive and pervasive landscape impacts. At least three floods in Iceland can be categorized as megafloods since they produced impressive bedrock canyons and giant fluvially-transported boulders. Glacier lake outburst floods (GLOFs) in Greenland might also have megaflood-type attributes given the enormous lake volumes drained. We therefore here present the first review of glacier outburst floods in Greenland: sites Isvand, Russell Glacier, Kuannersuit Glacier, Lake Tininnilik, two unnamed lakes near Amitsulooq Ice Cap, and Iluliallup Tasersua, Base Camp Lake, Lake Hullett, Qorlortorssup Tasia, Imaersartoq, Tordensø, North Midternæs and an outlet glacier of the A. P. Olsen Ice Cap. Overall, megaflood-type landscape impacts in Iceland tend to be best-preserved and most easily identified inland although there has also been extensive offshore sedimentation. There are very few reported impacts of glacier outburst floods in Greenland. In Greenland ice-dam failure causes frequent flooding compared to the volcanically-triggered floods in Iceland and this combined with the proximity of the Greenland glacier lakes to the coast means that most proglacial channels in Greenland are flood-hardened and most landscape impact is likely to be offshore in estuaries and fjords. Future floods with megaflood-type attributes will occur in Iceland induced by volcanic activity. In Greenland they will be induced by extreme weather and rapid ice melt. Any potential landscape impact of these future floods remains open to question. [ABSTRACT FROM AUTHOR]