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"Kargel, Jeffrey S"
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Review of the status and mass changes of Himalayan-Karakoram glaciers
by
VINCENT, CHRISTIAN
,
BERTHIER, ETIENNE
,
AZAM, MOHD FAROOQ
in
Albedo
,
Climate change
,
Cryosphere
2018
We present a comprehensive review of the status and changes in glacier length (since the 1850s), area and mass (since the 1960s) along the Himalayan-Karakoram (HK) region and their climate-change context. A quantitative reliability classification of the field-based mass-balance series is developed. Glaciological mass balances agree better with remotely sensed balances when we make an objective, systematic exclusion of likely flawed mass-balance series. The Himalayan mean glaciological mass budget was similar to the global average until 2000, and likely less negative after 2000. Mass wastage in the Himalaya resulted in increasing debris cover, the growth of glacial lakes and possibly decreasing ice velocities. Geodetic measurements indicate nearly balanced mass budgets for Karakoram glaciers since the 1970s, consistent with the unchanged extent of supraglacial debris-cover. Himalayan glaciers seem to be sensitive to precipitation partly through the albedo feedback on the short-wave radiation balance. Melt contributions from HK glaciers should increase until 2050 and then decrease, though a wide range of present-day area and volume estimates propagates large uncertainties in the future runoff. This review reflects an increasing understanding of HK glaciers and highlights the remaining challenges.
Journal Article
Massive collapse of two glaciers in western Tibet in 2016 after surge-like instability
by
Kääb, Andreas
,
Leinss, Silvan
,
Berthier, Etienne
in
Avalanches
,
Catastrophic collapse
,
Climate
2018
Surges and glacier avalanches are expressions of glacier instability, and among the most dramatic phenomena in the mountain cryosphere. Until now, the catastrophic collapse of a glacier, combining the large volume of surges and mobility of ice avalanches, has been reported only for the 2002 130 × 106 m3 detachment of Kolka Glacier (Caucasus Mountains), which has been considered a globally singular event. Here, we report on the similar detachment of the entire lower parts of two adjacent glaciers in western Tibet in July and September 2016, leading to an unprecedented pair of giant low-angle ice avalanches with volumes of 68 ± 2 × 106 m3 and 83 ± 2 × 106 m3. On the basis of satellite remote sensing, numerical modelling and field investigations, we find that the twin collapses were caused by climate- and weather-driven external forcing, acting on specific polythermal and soft-bed glacier properties. These factors converged to produce surge-like enhancement of driving stresses and massively reduced basal friction connected to subglacial water and fine-grained bed lithology, to eventually exceed collapse thresholds in resisting forces of the tongues frozen to their bed. Our findings show that large catastrophic instabilities of low-angle glaciers can happen under rare circumstances without historical precedent.
Journal Article
Transition of a small Himalayan glacier lake outburst flood to a giant transborder flood and debris flow
2022
Abstract
Glacial lake outburst floods (GLOFs) are a great concern for the Himalaya, as they can severely damage downstream populations and infrastructures. These floods originate at high altitudes and can flow down with enormous energy and change the terrain’s existing morphology. One such devastating event occurred on the night of 5 July 2016, from the inconspicuous Gongbatongsha Lake, located in the Poiqu basin, Eastern Himalaya. The Poiqu basin in the Tibetan Autonomous Region currently contains numerous big glacial lakes; however, this event originated from a small lake. The GLOF was triggered following heavy precipitation that led to a slope failure above the lake and deposition of debris into the lake, which breached the moraine dam and rapidly drained the entire lake. The flood damaged several downstream infrastructures, including the Arniko highway, the Upper Bhotekoshi hydropower plant, and several buildings as it made its way into the Bhotekoshi basin in Nepal. This study adopts a multi-model approach to reconstruct the GLOF trigger and the flood’s transformation into a severe debris flow. Proxies including flow discharge, flow velocity, runout distances were used to calibrate the model and validate the results. Results reveal that a debris flow of volume ranging between 3000 and 6000 m
3
from the headwall must have led to lake overfill, eventually leading to the GLOF event. The GLOF showed a significant increase in peak discharge from 618 to 4123 m
3
s
−1
at the Zhangzangbo-Bhotekoshi confluence. The average velocity of the flow is calculated to be ~ 5.5 m s
−1
. Reconstruction of the erosion and deposition dynamics show that maximum erosion occurred in the first 6.5 km, with maximum deposition occurring near the Upper Bhotekoshi hydropower station. The modeling indicates that the availability of the entrainable debris along the channel, likely from the previous landslides, amplified the event by three orders of magnitude-additional water ingested from the river. Overall, we demonstrate how the small-scale Gongbatongsha GLOF amplified downstream by incorporating pre-existing sediment in the valley and triggered damaging secondary landslides leading to an economic loss of > 70 million USD.
Journal Article
Sudden large-volume detachments of low-angle mountain glaciers – more frequent than thought?
2021
The detachment of large parts of low-angle mountain glaciers resulting in
massive ice–rock avalanches have so far been believed to be a unique type
of event, made known to the global scientific community first for the 2002
Kolka Glacier detachment, Caucasus Mountains, and then for the 2016
collapses of two glaciers in the Aru range, Tibet. Since 2016, several
so-far unrecognized low-angle glacier detachments have been recognized and
described, and new ones have occurred. In the current contribution, we
compile, compare, and discuss 20 actual or suspected large-volume detachments
of low-angle mountain glaciers at 10 different sites in the Caucasus, the
Pamirs, Tibet, Altai, the North American Cordillera, and the Southern Andes.
Many of the detachments reached volumes in the order of 10–100 million m3. The similarities and differences between the presented cases
indicate that glacier detachments often involve a coincidental combination
of factors related to the lowering of basal friction, high or increasing driving
stresses, concentration of shear stress, or low resistance to exceed
stability thresholds. Particularly soft glacier beds seem to be a common
condition among the observed events as they offer smooth contact areas
between the glacier and the underlying substrate and are prone to
till-strength weakening and eventually basal failure under high pore-water
pressure. Partially or fully thawed glacier bed conditions and the presence
of liquid water could thus play an important role in the detachments.
Surface slopes of the detached glaciers range between around 10∘
and 20∘. This may be low enough to enable the development of
thick and thus large-volume glaciers while also being steep enough to allow
critical driving stresses to build up. We construct a simple slab model to
estimate ranges of glacier slope and width above which a glacier may be able
to detach when extensively losing basal resistance. From this model we
estimate that all the detachments described in this study occurred due to a
basal shear stress reduction of more than 50 %. Most of the ice–rock
avalanches resulting from the detachments in this study have a particularly
low angle of reach, down to around 5∘, likely due to their high
ice content and connected liquefaction potential, the availability of soft
basal slurries, and large amounts of basal water, as well as the smooth
topographic setting typical for glacial valleys. Low-angle glacier
detachments combine elements and likely also physical processes of glacier
surges and ice break-offs from steep glaciers. The surge-like temporal
evolution ahead of several detachments and their geographic proximity to
other surge-type glaciers indicate the glacier detachments investigated can
be interpreted as endmembers of the continuum of surge-like glacier
instabilities. Though rare, glacier detachments appear to be more frequent
than commonly thought and disclose, despite local differences in conditions
and precursory evolutions, the fundamental and critical potential of
low-angle soft glacier beds to fail catastrophically.
Journal Article
Annual 30 m dataset for glacial lakes in High Mountain Asia from 2008 to 2017
by
Kargel, Jeffrey S
,
Watson, C. Scott
,
Chen, Fang
in
Altitude
,
Aquatic resources
,
Basin geometry
2021
Atmospheric warming is intensifying glacier melting and
glacial-lake development in High Mountain Asia (HMA), and this could
increase glacial-lake outburst flood (GLOF) hazards and impact water
resources and hydroelectric-power management. There is therefore a pressing
need to obtain comprehensive knowledge of the distribution and area of
glacial lakes and also to quantify the variability in their sizes and types
at high resolution in HMA. In this work, we developed an HMA glacial-lake
inventory (Hi-MAG) database to characterize the annual coverage of glacial
lakes from 2008 to 2017 at 30 m resolution using Landsat satellite imagery.
Our data show that glacial lakes exhibited a total area increase of
90.14 km2 in the period 2008–2017, a +6.90 % change relative to
2008 (1305.59±213.99 km2). The annual increases in the number
and area of lakes were 306 and 12 km2, respectively, and the greatest
increase in the number of lakes occurred at 5400 m elevation, which
increased by 249. Proglacial-lake-dominated areas, such as the
Nyainqêntanglha and central Himalaya, where more than half of the
glacial-lake area (summed over a 1∘ × 1∘
grid) consisted of proglacial lakes, showed obvious lake-area expansion.
Conversely, some regions of eastern Tibetan mountains and Hengduan Shan,
where unconnected glacial lakes occupied over half of the total lake area in
each grid, exhibited stability or a slight reduction in lake area. Our
results demonstrate that proglacial lakes are a main contributor to recent
lake evolution in HMA, accounting for 62.87 % (56.67 km2) of the
total area increase. Proglacial lakes in the Himalaya ranges alone accounted
for 36.27 % (32.70 km2) of the total area increase. Regional
geographic variability in debris cover, together with trends in warming and
precipitation over the past few decades, largely explains the current
distribution of supraglacial- and proglacial-lake area across HMA. The Hi-MAG
database is available at https://doi.org/10.5281/zenodo.4275164
(Chen et al., 2020), and it can be used for studies of the complex interactions between glaciers, climate and glacial lakes, studies of GLOFs, and water resources.
Journal Article
The cost of rapid and haphazard urbanization: lessons learned from the Freetown landslide disaster
2019
Urbanization has been linked to destructive geo-hazards that can cause loss of life, destruction of property, and environmental damage. On August 14, 2017, a devastating geo-hazard chain—a debris slide, debris flow, and sediment-laden flood—in Freetown, Sierra Leone resulted in at least 500 deaths and over 600 missing persons and the destruction of hundreds of houses. This study uses 10 years of high-resolution satellite images to conduct a remote sensing analysis of the disaster. Although rainfall was the trigger, rapid and haphazard urbanization acted to increase both hazard and vulnerability. Specifically, poor urban planning with inadequate consideration of risk led to housing construction in dangerous areas; clearance of hillside vegetation increased erosion potential; very low cost buildings using frail construction material and methods lacked resilience; and insufficient risk management led to weak emergency response.
Journal Article
Climate change and the global pattern of moraine-dammed glacial lake outburst floods
by
Kargel, Jeffrey S
,
Klimeš, Jan
,
Wiltshire, Andy
in
Anthropogenic factors
,
Climate change
,
Climate effects
2018
Despite recent research identifying a clear anthropogenic impact on glacier recession, the effect of recent climate change on glacier-related hazards is at present unclear. Here we present the first global spatio-temporal assessment of glacial lake outburst floods (GLOFs) focusing explicitly on lake drainage following moraine dam failure. These floods occur as mountain glaciers recede and downwaste. GLOFs can have an enormous impact on downstream communities and infrastructure. Our assessment of GLOFs associated with the rapid drainage of moraine-dammed lakes provides insights into the historical trends of GLOFs and their distributions under current and future global climate change. We observe a clear global increase in GLOF frequency and their regularity around 1930, which likely represents a lagged response to post-Little Ice Age warming. Notably, we also show that GLOF frequency and regularity – rather unexpectedly – have declined in recent decades even during a time of rapid glacier recession. Although previous studies have suggested that GLOFs will increase in response to climate warming and glacier recession, our global results demonstrate that this has not yet clearly happened. From an assessment of the timing of climate forcing, lag times in glacier recession, lake formation and moraine-dam failure, we predict increased GLOF frequencies during the next decades and into the 22nd century.
Journal Article
The hazardous 2017-2019 surge and river damming by Shispare Glacier, Karakoram
2020
In 2017-2019 a surge of Shispare Glacier, a former tributary of the once larger Hasanabad Glacier (Hunza region), dammed the proglacial river of Muchuhar Glacier, which formed an ice-dammed lake and generated a small Glacial Lake Outburst Flood (GLOF). Surge movement produced the highest recorded Karakoram glacier surface flow rate using feature tracking (~18 ± 0.5 m d
) and resulted in a glacier frontal advance of 1495 ± 47 m. The surge speed was less than reports of earlier Hasanabad advances during 1892/93 (9.3 km) and 1903 (9.7 km). Surges also occurred in 1973 and 2000-2001. Recent surges and lake evolution are examined using feature tracking in satellite images (1990-2019), DEM differencing (1973-2019), and thermal satellite data (2000-2019). The recent active phase of Shispare surge began in April 2018, showed two surface flow maxima in June 2018 and May 2019, and terminated following a GLOF on 22-23 June 2019. The surge likely had hydrological controls influenced in winter by compromised subglacial flow and low meltwater production. It terminated during summer probably because increased meltwater restored efficient channelized flow. We also identify considerable heterogeneity of movement, including spring/summer accelerations.
Journal Article
Evolution and Controls of Large Glacial Lakes in the Nepal Himalaya
2018
Glacier recession driven by climate change produces glacial lakes, some of which are hazardous. Our study assesses the evolution of three of the most hazardous moraine-dammed proglacial lakes in the Nepal Himalaya-Imja, Lower Barun, and Thulagi. Imja Lake (up to 150 m deep; 78.4 × 106 m3 volume; surveyed in October 2014) and Lower Barun Lake (205 m maximum observed depth; 112.3 × 106 m3 volume; surveyed in October 2015) are much deeper than previously measured, and their readily drainable volumes are slowly growing. Their surface areas have been increasing at an accelerating pace from a few small supraglacial lakes in the 1950s/1960s to 1.33 km2 and 1.79 km2 in 2017, respectively. In contrast, the surface area (0.89 km2) and volume of Thulagi lake (76 m maximum observed depth; 36.1 × 106 m3; surveyed in October 2017) has remained almost stable for about two decades. Analyses of changes in the moraine dams of the three lakes using digital elevation models (DEMs) quantifies the degradation of the dams due to the melting of their ice cores and hence their natural lowering rates as well as the potential for glacial lake outburst floods (GLOFs). We examined the likely future evolution of lake growth and hazard processes associated with lake instability, which suggests faster growth and increased hazard potential at Lower Barun lake.
Journal Article
Exploring the evidence of Middle Amazonian aquifer sedimentary outburst residues in a Martian chaotic terrain
2023
Abstract The quest for past Martian life hinges on locating surface formations linked to ancient habitability. While Mars' surface is considered to have become cryogenic ~3.7 Ga, stable subsurface aquifers persisted long after this transition. Their extensive collapse triggered megafloods ~3.4 Ga, and the resulting outflow channel excavation generated voluminous sediment eroded from the highlands. These materials are considered to have extensively covered the northern lowlands. Here, we show evidence that a lacustrine sedimentary residue within Hydraotes Chaos formed due to regional aquifer upwelling and ponding into an interior basin. Unlike the northern lowland counterparts, its sedimentary makeup likely consists of aquifer-expelled materials, offering a potential window into the nature of Mars' subsurface habitability. Furthermore, the lake’s residue’s estimated age is ~1.1 Ga (~3.2 Ga post-peak aquifer drainage during the Late Hesperian), enhancing the prospects for organic matter preservation. This deposit’s inferred fine-grained composition, coupled with the presence of coexisting mud volcanoes and diapirs, suggest that its source aquifer existed within abundant subsurface mudstones, water ice, and evaporites, forming part of the region’s extremely ancient (~ 4 Ga) highland stratigraphy. Our numerical models suggest that magmatically induced phase segregation within these materials generated enormous water-filled chambers. The meltwater, originating from varying thermally affected mudstone depths, could have potentially harbored diverse biosignatures, which could have become concentrated within the lake’s sedimentary residue. Thus, we propose that Hydraotes Chaos merits priority consideration in future missions aiming to detect Martian biosignatures.
Journal Article