Ice-marginal Lake Research Articles

Altimetry-based ice-marginal lake water level changes in Greenland

Greenland holds over 3300 ice-marginal lakes, serving as natural reservoirs for outflow of meltwater to the ocean. A sudden release of water can largely influence ecosystems, landscape morphology, ice dynamics and cause flood hazards. While large-scale studies of glacial lake outburst floods (GLOFs) have been conducted in many glaciated regions, Greenland remains understudied. Here we use altimetry data to provide the first Greenland-wide inventory of ice-marginal lake water level changes, studying over 1100 lakes from 2003–2023, revealing a diverse range of lake behaviors. Around 60% of the lakes exhibit minimal fluctuations, while 326 lakes have drained, collectively contributing to 541 observed GLOFs from 2008–2022. These GLOFs vary substantially in magnitude and frequency, with the highest concentration observed in the North and Northeast regions. Our results show substantial annual differences in the number of GLOFs with a notable peak in 2019, coinciding with a year marked by extreme runoff. Our method detected a 1200% increase in the number of draining lakes compared to existing historical databases. This highlights a large underreporting of GLOF events and emphasizes the pressing need for a deeper understanding of the mechanisms behind and the consequences of these dramatic events.

Palaeolake Jeinimeni and ice-marginal geomorphology of the central Patagonian Lago General Carrera/Buenos Aires ice-lobe (46.5°S)

Robust geomorphological interpretations of ice-marginal glacial, meltwater and palaeolake landforms are needed to constrain models of landform evolution that can be used to underpin high-resolution geochronologies of deglaciation. The Lago General Carrera/Bueno Aires (LGCBA) ice lobe of the former Patagonian Ice Sheet is one of the most researched in Patagonia, yet there remain contrasting landform evolution models partly because the spatiotemporal relationships between landforms in the LGCBA basin and tributary valleys have not been fully investigated. To this end we present a detailed, high-resolution glacial geomorphological map of the Los Antiguos sector of the LGCBA basin, and the tributary Río Jeinimeni valley, alongside sediment-landform assemblages from a broad suite of ice-marginal, subglacial, glaciolacustrine, glaciofluvial and paraglacial landforms. We introduce evidence for a previously unmapped ice-dammed lake within the Jeinimeni valley, which may have existed during the Last Glacial Maximum. Multiple isolated, ice-marginal proglacial lakes, which formed during the recession of the LGCBA ice lobe, were also mapped. The landform evidence is synthesised into a refined landscape evolution model for the LGCBA basin and Jeinimeni valley during the Last Glacial Interglacial Transition. The data presented demonstrate that previously reconstructed high LGCBA lake-level stands above 500 m asl were likely glaciolacustrine landforms created by ice-marginal lakes dammed by the LGCBA ice lobe. The mapping in the Jeinimeni valley highlights the potential for renewed dating investigations of landforms in tributary valleys to provide maximum limiting ages for the retreat of their associated glaciers. Furthermore, the identification of glaciolacustrine varved sediments associated with palaeolake Jeinimeni and the Los Antiguos sector of the LGCBA palaeolake, highlights the potential of these annually-resolved archives to infer spatiotemporal dynamics of main ice-lobe/tributary glaciers to improve palaeoenvironmental and palaeoclimatic reconstructions in the region.

Terminus thinning drives recent acceleration of a Greenlandic lake-terminating outlet glacier

Abstract Ice-contact proglacial lakes affect ice dynamics and the transition of glacier termini from land- to lake-terminating has been shown to cause ice flow acceleration. In recent decades, the number and size of Greenlandic ice-marginal lakes has increased, highlighting the need to further understand these lake-terminating ice-margins as their influence on ice sheet mass balance increases. Here, time series of satellite-derived observations of ice velocity, surface elevation, and terminus position were generated at a lake-terminating outlet glacier, Isortuarsuup Sermia, and the nearby land-terminating Kangaasarsuup Sermia in south-west Greenland. At Isortuarsuup Sermia, annual surface velocity at the terminus increased by a factor of 2.5 to 214 ± 4 m yr−1 (2013–2021), with the magnitude of this acceleration declining with distance up-glacier. Meanwhile, near-terminus surface elevation changed at a rate of −2.3 ± 1.1 m yr−1 (2012–2021). Conversely, velocity change at Kangaasarsuup Sermia was minimal, while surface elevation change was approximately half at comparable elevations (−1.2 ± 0.3 m yr−1). We attribute these dynamic differences to thinning at Isortuarsuup Sermia and subsequent retreat from a stabilising sublacustrine moraine, and emphasise the potential of proglacial lakes to enhance future rates of mass loss from the Greenland Ice Sheet.

Outbursts from an ice-marginal lake in Antarctica in 1969–1971 and 2017, revealed by aerial photographs and satellite data

The liquid water around the Antarctic Ice Sheet plays a key role in modulating both the vulnerability of ice shelves to hydrofracturing and ice discharge from outlet glaciers. Therefore, it needs to be adequately constrained for precise future projections of ice-mass loss and global sea-level rise. Although glacial lake outburst floods (GLOFs) pose one of the greatest risks in glacierized mountainous regions, any long-term monitoring of Antarctic ice-marginal lakes and their associated potential for GLOFs has been neglected until recently owing to the limited number of such events reported in Antarctica. Here we present direct evidence of repeated GLOFs from Lake Kaminotani-Ike, an ice-sheet-dammed lake in East Antarctica, via an analysis of historical aerial photographs and recent satellite data. Two GLOFs occurred in 1969–1971 and 2017, with discharge volumes of (8.6 ± 1.5) × 107 and (7.1 ± 0.4) × 107 m3, respectively, making them two of the largest GLOFs in Antarctica. A southerly oceanward pathway beneath the ice sheet is the most likely drainage route of these GLOF events based on the available surface- and bed-elevation datasets. Furthermore, the 2017 event occurred during the austral winter, thereby implying the possibility of year-round active subglacial networks in Antarctica. Our results highlight that studies on Antarctic ice-marginal lakes provide an opportunity to better understand Antarctic hydrological processes and emphasize the need for both detailed monitoring of ice-marginal lakes and detailed surveying of the subglacial environments of the Antarctic Ice Sheet.

A window into development of a complex ice-marginal lake prior to the Late Glacial Maximum (LGM) in Austria

Abstract Although the retreat process of glaciers from the Late Glacial Maximum (LGM) is well documented, high-resolution insight into conditions prior to the maximum is lacking in the eastern European Alps, resulting in a gap in our understanding about the processes associated with this important climatic tipping point. We describe an outstanding sand and gravel outcrop at Gröbming in the Enns Valley (Ennstal), Austria, that represents the development of a delta complex that debouched into a large body of water that we name paleo-Lake Gröbming, fed by a major valley glacier. The succession consists of sands bearing climbing ripples, parallel laminations, and supercritical bed forms (bottomsets) overlain by meter-scale gravelly foresets. Topsets comprise gravels. We argue that sustained accumulation of supercritical bed forms required a jet efflux feeder mechanism best explained by a direct glacial meltwater source. Complex vertical and lateral repetition of this tripartite succession is observed, with sequence stratigraphic analysis permitting us to argue that stratal complexity is attributable to base-level changes in paleo-Lake Gröbming resulting from dam breaches of the lake. Thus, application of well-established sequence stratigraphic approaches to Quaternary ice-marginal successions in the Alps has significant potential to yield unprecedented insights into conditions prior to the LGM.

Characterizing 4 decades of accelerated glacial mass loss in the west Nyainqentanglha Range of the Tibetan Plateau

Abstract. Glacier retreat is altering the water regime of the Tibetan Plateau (TP) as the region's climate changes, but there remain substantial gaps in our knowledge of recent glacier loss in this region due to the difficulty of making direct high-mountain observations, and this limits our ability to predict the future of this important water resource. Here, we assessed 44 years of glacier area and volume changes in the major west Nyainqentanglha Range (WNR) that supplies meltwater to the densely populated Lhasa River basin and Nam Co, the second largest endorheic lake on the TP. Between the two periods 1976–2000 and 2000–2020, we found that the glacier areal retreat rate more than doubled (from -0.54±0.21 % a−1 to -1.17±0.30 % a−1), and surface lowering also accelerated (from -0.26±0.09 to -0.37±0.15 m w.e a−1) with particularly intense melting after 2014. This acceleration is similar in both timing and magnitude to that observed for Himalayan glaciers farther south. Besides, the areal retreat rate and mass loss rate of most glaciers in the WNR were not synchronized. To understand the sensitivity of WNR glaciers to climate forcing, we examined the effects of topography, debris cover and the presence of proglacial lakes on our observed changes. We found consistently faster areal retreat but slower thinning rates on steeper slopes and an inconsistent relationship with aspect. We concluded that our observed spatial and temporal patterns of glacier change were dominated by observed local variations in temperature and precipitation, the melt-reducing role of supraglacial debris, and the increasing influence of ice-marginal lakes on glacier ablation.

Glacier retreat analysis in the context of climate change impact over the Satopanth (SPG) and Bhagirathi-Kharak (BKG) glaciers in the Mana basin of the Central Himalaya, India: A geospatial approach

• Glacier retreat footprints over the Mana Basin. • Spatio-temporal changes in the snout/glacier over the period of 50 years. • Estimation of ice velocity using the SAR technique. • Negative trend in snow cover area and increase of temperature. This study explores the dynamics of the Satopanth (SPG) and Bhagirathi-Kharak (BKG) glaciers of the Mana basin in the Central Himalayan region of India under the scenario of climate change. The spatio-temporal changes in the glacier area, volume, and shift in snout positions during the period from 1968 to 2017 were assessed based on the CORONA photograph and satellite data . The study also intended to identify the common drifts in glacier areas for observing temporal and seasonal (during the winter-spring-summer transition) changes in the glacial landscapes and ably evaluate glacier velocity and ice-marginal lake stage. The ice velocity was found to vary from 0.117 md −1 to 0.165 md −1 for January to October months. It was found to have increased during the winter-spring-summer transition periods used to estimate the ice flow intensity and its phase information regular basis. Besides this, the linear trends of the MOD11A2 land surface temperature product were obtained and temperature variability has been analyzed from 2001 to 2020. The results show significant warming over the basin along with a significant negative trend in snow cover area during different seasons. The derived information is quite useful in analyzing the climate change footprints such as snowline movement, snow volume changes, and glacier mass balance-related studies.

Coincident evolution of glaciers and ice-marginal proglacial lakes across the Southern Alps, New Zealand: Past, present and future

Global glacier mass loss is causing expansion of proglacial landscapes and producing meltwater that can become impounded as lakes within natural topographic depressions or ‘overdeepenings’. It is important to understand the evolution of these proglacial landscapes for water resources, natural hazards and ecosystem services. In this study we (i) overview contemporary loss of glacier ice across the Southern Alps of New Zealand, (ii) analyse ice-marginal lake development since the 1980s, (iii) utilise modelled glacier ice thickness to suggest the position and size of future lakes, and (iv) employ a large-scale glacier evolution model to suggest the timing of future lake formation and future lake expansion rate. In recent decades, hundreds of Southern Alps glaciers have been lost and those remaining have fragmented both by separation of tributaries and by detachment of ablation zones. Glaciers with ice-contact margins in proglacial lakes (n > 0.1 km2 = 20 in 2020) have experienced the greatest terminus retreat and typically twice as negative mass balance compared to similar-sized land-terminating glaciers. Our analysis indicates a positive relationship between mean glacier mass balance and rate of lake growth (R2 = 0.34) and also with length of an ice-contact lake boundary (R2 = 0.44). We project sustained and relatively homogenous glacier volume loss for east-draining basins but in contrast a heterogeneous pattern of volume loss for west-draining basins. Our model results show that ice-marginal lakes will increase in combined size by ~150% towards 2050 and then decrease to 2100 as glaciers disconnect from them. Overall, our findings should inform (i) glacier evolution models into which ice-marginal lake effects need incorporating, (ii) studies of rapid landscape evolution and especially of meltwater and sediment delivery, and (iii) considerations of future meltwater supply and water quality.

An inventory of Norway's glaciers and ice-marginal lakes from 2018–19 Sentinel-2 data

AbstractWe used Sentinel-2 satellite imagery at 10 m resolution to map the extent of Norway's glaciers and ice-marginal lakes over 2018–19. We applied a standardized semi-automated band ratio method to derive glacier outlines and ice-marginal lakes. To optimise the results, we manually edited the ice-lake interfaces, debris, snow and parts of the glaciers situated under shadow. We compared our Sentinel-2 derived outlines with very high-resolution aerial orthophotos and Pléiades satellite orthoimages. Glaciers larger than 0.3 km2have area differences within 7%, whereas values are larger for smaller glaciers. The orthophotos and orthoimages provide more details and a higher mapping accuracy for individual glaciers, but require manual digitisation, have smaller spatial and temporal coverage and can have adverse snow conditions. We found a total glacier area of 2328 ± 70 km2of which the ten largest glaciers accounted for 52%. The glacier area decreased 15% since the previous inventory (Landsat data from 1999 to 2006), the reduction being largest in northern Norway (22%) compared to southern Norway (10%). We detected more than 2000 previously undetected smaller glaciers and ice patches (covering 37 km2) and 360 new ice-marginal lakes.

Dam type and lake location characterize ice-marginal lake area change in Alaska and NW Canada between 1984 and 2019

Abstract. Ice-marginal lakes impact glacier mass balance, water resources, and ecosystem dynamics and can produce catastrophic glacial lake outburst floods (GLOFs) via sudden drainage. Multitemporal inventories of ice-marginal lakes are a critical first step in understanding the drivers of historic change, predicting future lake evolution, and assessing GLOF hazards. Here, we use Landsat-era satellite imagery and supervised classification to semi-automatically delineate lake outlines for four ∼5-year time periods between 1984 and 2019 in Alaska and northwest Canada. Overall, ice-marginal lakes in the region have grown in total number (+183 lakes, 38 % increase) and area (+483 km2, 59 % increase) between the time periods of 1984–1988 and 2016–2019. However, changes in lake numbers and area were notably unsteady and nonuniform. We demonstrate that lake area changes are connected to dam type (moraine, bedrock, ice, or supraglacial) and topological position (proglacial, detached, unconnected, ice, or supraglacial), with important differences in lake behavior between the sub-groups. In strong contrast to all other dam types, ice-dammed lakes decreased in number (six fewer, 9 % decrease) and area (−51 km2, 40 % decrease), while moraine-dammed lakes increased (56 more, 26 % and +479 km2, 87 % increase for number and area, respectively) at a faster rate than the average when considering all dam types together. Proglacial lakes experienced the largest area changes and rate of change out of any lake position throughout the period of study and moraine-dammed lakes which experienced the largest increases are associated with clean-ice glaciers (<19 % debris cover). By tracking individual lakes through time and categorizing lakes by dam type, subregion, and topological position, we are able to parse trends that would otherwise be aliased if these characteristics were not considered. This work highlights the importance of such lake characterization when performing ice-marginal lake inventories and provides insight into the physical processes driving recent ice-marginal lake evolution.

Short-Term Variability in Alaska Ice-Marginal Lake Area: Implications for Long-Term Studies

Lakes in direct contact with glaciers (ice-marginal lakes) are found across alpine and polar landscapes. Many studies characterize ice-marginal lake behavior over multi-decadal timescales using either episodic ~annual images or multi-year mosaics. However, ice-marginal lakes are dynamic features that experience short-term (i.e., day to year) variations in area and volume superimposed on longer-term trends. Through aliasing, this short-term variability could result in erroneous long-term estimates of lake change. We develop and implement an automated workflow in Google Earth Engine to quantify monthly behavior of ice-marginal lakes between 2013 and 2019 across south-central Alaska using Landsat 8 imagery. We employ a supervised Mahalanobis minimum-distance land cover classifier incorporating three datasets found to maximize classifier performance: shortwave infrared imagery, the normalized difference vegetation index (NDVI), and spatially filtered panchromatic reflectance. We observe physically-meaningful ice-marginal lake area variance on sub-annual timescales, with the median area fluctuation of an ice-marginal lake found to be 10.8% of its average area. The median signal (slow lake growth) to noise (physically-meaningful short-term area variability) ratio is 1.5:1, indicating that short-term variability is responsible for ~33% of observed area change in the median ice-marginal lake. The magnitude of short-term area variability is similar for ice-marginal and nonglacial lakes, suggesting that the cause of observed variations is not of glacial origin. These data provide a new context for interpreting behaviors observed in multi-decadal studies and encourage attention to sub-annual behavior of ice-marginal lakes even in long-term studies.

Gulf of Alaska ice-marginal lake area change over the Landsat record and potential physical controls

Abstract. Lakes in contact with glacier margins can impact glacier evolution as well as the downstream biophysical systems, flood hazard, and water resources. Recent work suggests positive feedbacks between glacier wastage and ice-marginal lake evolution, although precise physical controls are not well understood. Here, we quantify ice-marginal lake area change in understudied northwestern North America from 1984–2018 and investigate climatic, topographic, and glaciological influences on lake area change. We delineate time series of sampled lake perimeters (n=107 lakes) and find that regional lake area has increased 58 % in aggregate, with individual proglacial lakes growing by 1.28 km2 (125 %) and ice-dammed lakes shrinking by 0.04 km2 (−15 %) on average. A statistical investigation of climate reanalysis data suggests that changes in summer temperature and winter precipitation exert minimal direct influence on lake area change. Utilizing existing datasets of observed and modeled glacial characteristics, we find that large, wide glaciers with thick lake-adjacent ice are associated with the fastest rate of lake area change, particularly where they have been undergoing rapid mass loss in recent times. We observe a dichotomy in which large, low-elevation coastal proglacial lakes have changed most in absolute terms, while small, interior lakes at high elevation have changed most in relative terms. Generally, the fastest-changing lakes have not experienced the most dramatic temperature or precipitation change, nor are they associated with the highest rates of glacier mass loss. Our work suggests that, while climatic and glaciological factors must play some role in determining lake area change, the influence of a lake's specific geometry and topographic setting overrides these external controls.

Ice-marginal lakes associated with enhanced recession of the Greenland Ice Sheet

There has been a progressive increase in the number and area of ice-marginal lakes situated along the south-western margin of the Greenland Ice Sheet (GrIS) since the 1980s. The increased prevalence of ice-marginal lakes is notable because of their capacity to enhance mass loss and ice-margin recession through a number of thermo-mechanical controls. Although such effects have been extensively documented at alpine glaciers, an understanding of how ice-marginal lakes impact the dynamics of the GrIS has been limited by a sparsity of observational records. This study employs the Landsat archive to conduct a multi-decadal, regional-scale statistical analysis of ice-margin advance and recession along a ~ 5000 km length of the south-western margin of the GrIS, incorporating its terrestrial, lacustrine and marine ice-margins. We reveal an extended and accelerating phase of ice-margin recession in south-west Greenland from 1992 onwards, irrespective of margin type, but also observe considerable heterogeneity in the behaviour of the different ice-marginal environments. Marine ice-margins exhibited the greatest magnitude and variability in ice-margin change, however lacustrine termini were notable for a progressive increase in ice-margin recession rates from 1987 to 2015, which increasingly outpaced those measured at terrestrial ice-margins. Furthermore, significant correlations were identified between lake parameters and rates of lacustrine ice-margin recession, including lake area, latitude, altitude and the length of the lake – ice-margin interface. These results suggest that ice-marginal lakes have become increasingly important drivers of ice-margin recession and thus mass loss at the GrIS, however further research is needed to better parameterise the causal connections between ice-marginal lake evolution and enhanced ice-margin recession. More widely, a detailed understanding of the impacts of ice-marginal lakes on ice-margin dynamics across Greenland is increasingly necessary to accurately forecast the response of the ice sheet to enhanced ice-marginal lake prevalence and thus refine projections of recession, mass loss and sea level rise.

Greenland-wide inventory of ice marginal lakes using a multi-method approach

Ice marginal lakes are a dynamic component of terrestrial meltwater storage at the margin of the Greenland Ice Sheet. Despite their significance to the sea level budget, local flood hazards and bigeochemical fluxes, there is a lack of Greenland-wide research into ice marginal lakes. Here, a detailed multi-sensor inventory of Greenland’s ice marginal lakes is presented based on three well-established detection methods to form a unified remote sensing approach. The inventory consists of 3347 (pm 8%) ice marginal lakes (>0.05,{{text{ km }}^{2}}) detected for the year 2017. The greatest proportion of lakes lie around Greenland’s ice caps and mountain glaciers, and the southwest margin of the ice sheet. Through comparison to previous studies, a sim 75% increase in lake frequency is evident over the west margin of the ice sheet since 1985. This suggests it is becoming increasingly important to include ice marginal lakes in future sea level projections, where these lakes will form a dynamic storage of meltwater that can influence outlet glacier dynamics. Comparison to existing global glacial lake inventories demonstrate that up to 56% of ice marginal lakes could be unaccounted for in global estimates of ice marginal lake change, likely due to the reliance on a single lake detection method.

Comparing the Applicability of Sentinel-1 and Sentinel-2 for Mapping the Evolution of Ice-marginal Lakes in Southeast Iceland

Monitoring ice-marginal lakes is important for glaciological and geomorphological studies, as well as hazard and risk assessment. Sentinel-1 synthetic aperture radar (SAR) and Sentinel-2 optical data opened a new era for multi-temporal analysis and studying geomorphological changes. The purpose of this study is to compare the applicability of Sentinel-1 and Sentinel-2 data for mapping the changes in ice-marginal lake areas at the southern margin of the Vatnajökull ice cap, southeast Iceland, between 2016 and 2020. We semi-automatically mapped the ice-marginal lakes with object-based image analysis (OBIA) and based on image time series using 1) the polarization products derived from Sentinel-1 data, and 2) the spectral information of Sentinel-2 data, and compared the results. Our results show that Sentinel-1 performed better regarding the detection of the number of ice-marginal lakes, whereas Sentinel-2 performed better regarding lake delineation. Moreover, we discuss the applicability of optical and SAR data for mapping and monitoring the evolution of ice-marginal lakes.

Toward Numerical Modeling of Interactions Between Ice-Marginal Proglacial Lakes and Glaciers

Global climate change is evidently manifest in disappearing mountain glaciers and receding and thinning ice sheet margins. Concern about contemporaneous proglacial lake development has spurred an emerging area of research seeking to quantitatively understand lake - glacier interactions. This perspectives article identifies spatio-temporal disparity between the coverage of field data, remote sensing observations and numerical modeling efforts. Throughout, an overview of the physical effects of lakes on glaciers and on ice sheet margins is provided, drawing evidence together from very recent and high-impact studies of both modern glaciology and of the Quaternary record. We identify and discuss six challenges for numerical modeling of lake - glacier interactions, namely that there are meltwater exchanges between glaciers and ice-marginal lakes, lake bathymetry and glacier bed topography are often unknown, lake - glacier interactions affect the longitudinal stress regime of glaciers, lake water temperature affects glacier melting but is very poorly constrained, the interactions persist with considerable spatio-temporal variability and with boundary migration, and data for model parameterization and validation is extremely scarce. Overall, we contend that numerical modeling is a key frontier in the cryospheric sciences to deliver process understanding of lake - glacier interactions.

Ice-marginal lake hydrology and the seasonal dynamical evolution of Kennicott Glacier, Alaska

AbstractGlacier basal motion is responsible for the majority of ice flux on fast-flowing glaciers, enables rapid changes in glacier motion and provides the means by which glaciers shape alpine landscapes. In an effort to enhance our understanding of basal motion, we investigate the evolution of glacier velocity and ice-marginal lake stage on Kennicott Glacier, Alaska, during the spring–summer transition, a time when subglacial drainage is undergoing rapid change. A complicated record of > 50 m fill-and-drain sequences on a hydraulically-connected ice-marginal lake likely reflects the punctuated establishment of efficient subglacial drainage as the melt season begins. The rate of change of lake stage generally correlates with diurnal velocity maxima, both in timing and magnitude. At the seasonal scale, the up-glacier progression of enhanced summer basal motion promotes uniformity of daily glacier velocity fluctuations throughout the 10 km study reach, and results in diurnal velocity patterns suggesting increasingly efficient meltwater delivery to and drainage from the subglacial channel system. Our findings suggest the potential of using an ice-marginal lake as a proxy for subglacial water pressure, and show how widespread basal motion affects bulk glacier behavior.

A stationary impulse-radar system for autonomous deployment in cold and temperate environments

AbstractStationary ice-penetrating radar (sIPR) systems can be used to monitor temporal changes in electromagnetically sensitive properties of glaciers and ice sheets. We describe a system intended for autonomous operation in remote glacial environments, and document its performance during deployments in cold and temperate settings. The design is patterned after an existing impulse radar system, with the addition of a fibre-optic link and timing module to control transmitter pulses, a micro-UPS (uninterruptable power supply) to prevent uncontrolled system shutdown and a customized satellite telemetry scheme. Various implementations of the sIPR were deployed on the Kaskawulsh Glacier near an ice-marginal lake in Yukon, Canada, for 44–77 days in summers 2014, 2015 and 2017. Pronounced perturbations to englacial radiostratigraphy were observed commensurate with lake filling and drainage, and are interpreted as changes in englacial water storage. Another sIPR was deployed in 2015–2016 on ice island PII-A-1-f, which originated from the Petermann Glacier in northwest Greenland. This system operated autonomously for almost a year during which changes in thickness of the ice column were clearly detected.

Glaciohydraulic seismic tremors on an Alpine glacier

Abstract. Hydraulic processes impact viscous and brittle ice deformation. Water-driven fracturing as well as turbulent water flow within and beneath glaciers radiate seismic waves which provide insights into otherwise hard-to-access englacial and subglacial environments. In this study, we analyze glaciohydraulic tremors recorded by four seismic arrays installed in different parts of Glacier de la Plaine Morte, Switzerland. Data were recorded during the 2016 melt season including the sudden subglacial drainage of an ice-marginal lake. Together with our seismic data, discharge, lake level, and ice flow measurements provide constraints on glacier hydraulics. We find that the tremors are generated by subglacial water flow, in moulins, and by icequake bursts. The dominating process can vary on sub-kilometer and sub-daily scales. Consistent with field observations, continuous source tracking via matched-field processing suggests a gradual up-glacier progression of an efficient drainage system as the melt season progresses. The ice-marginal lake likely connects to this drainage system via hydrofracturing, which is indicated by sustained icequake signals emitted from the proximity of the lake basin and starting roughly 24 h prior to the lake drainage. To estimate the hydraulics associated with the drainage, we use tremor–discharge scaling relationships. Our analysis suggests a pressurization of the subglacial environment at the drainage onset, followed by an increase in the hydraulic radii of the conduits and a subsequent decrease in the subglacial water pressure as the capacity of the drainage system increases. The pressurization is in phase with the drop in the lake level, and its retrieved maximum coincides with ice uplift measured via GPS. Our results highlight the use of cryo-seismology for monitoring glacier hydraulics.

Terminus lakes on the south side of Vatnajökull ice cap, SE-Iceland

Many ice-marginal lakes have formed in front of glacier termini in Iceland in recent decades due to climate warming, particularly at the southern margin of Vatnajökull ice cap where several such lakes grow year-by-year at present. At the same time, most glacier-dammed lakes at the lateral ice margins have shrunk or disappeared because of glacier thinning, and jökulhlaups released from them have become smaller. This paper describes changes in glacial lakes in SE-Iceland, from Skeiðarárjökull west of Öræfi to Hoffellsjökull in Hornafjörður. Lakes started to form in front of several glaciers in this area in the 1930s but most did not grow much until the 1990s, except for Jökulsárlón by Breiðamerkurjökull, which has grown steadily since before the middle of the last century. Currently, there are growing terminus lakes by all the main south-flowing outlet glaciers of Vatnajökull, with a combined area of ~60 km². The subglacial landscape upstream of the termini indicates that the lakes will continue to grow in the coming decades as a consequence of glacier downwasting if the climate warms as projected. These lakes affect the ice flow and the mass and energy balance of the respective glaciers because of their effect on the force balance of the terminus region, the calving of ice into the lakes, and the absorption of heat spent for melting of calved ice fragments and the terminus ice front. The lakes can cause hazard to settlements and travellers in the adjacent area, as landslides on the glaciers that propagate into the lakes can create tsunami waves with a high run-up and sudden, very dangerous flash floods in the glacier forelands.