What drives large-scale glacier detachments? Insights from Flat Creek glacier, St. Elias Mountains, Alaska

Jacquemart, Mylène; Loso, Michael G.; Leopold, Matthias; Welty, Ethan; Berthier, Étienne; Hansen, J. S.; Sykes, John; Tiampo, K. F.

doi:10.1130/g47211.1

Cited by 41 publications

(32 citation statements)

References 25 publications

(32 reference statements)

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“…From a hazards and risk perspective, the question of how warming temperatures and changing patterns of precipitation as a result of climate change will impact rock avalanche frequency (recurrence intervals) and magnitude is important to consider because rock avalanches often entrain material and grow volumetrically as they travel downslope (e.g., Bessette-Kirton et al, 2018), travel long (>5 km) distances (Post, 1967;McSaveney, 1978;Evans and Clague, 1999;McSaveney, 2002;Huggel et al, , 2007Huggel et al, , 2010Evans et al, 2009;Geertsema, 2012;Guthrie et al, 2012;Jacquemart et al, 2020), and can create cascading hazards (e.g., outburst floods or tsunamis) when they impact mountain lakes or fiords (Miller, 1960;Bessette-Kirton et al, 2017;Haeberli et al, 2017;Higman et al, 2018). These characteristics make rock avalanches a risk to humans in areas well downstream from locations where they initiate (e.g., Evans et al, 2009;Duhart et al, 2019;Mergili et al, 2020;Walter et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

A 36-Year Record of Rock Avalanches in the Saint Elias Mountains of Alaska, With Implications for Future Hazards

Bessette-Kirton

Coe

2020

Front. Earth Sci.

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Glacial retreat and mountain-permafrost degradation resulting from rising global temperatures have the potential to impact the frequency and magnitude of landslides in glaciated environments. Several recent events, including the 2015 Taan Fiord rock avalanche, which triggered a tsunami with one of the highest wave runups ever recorded, have called attention to the hazards posed by landslides in regions like southern Alaska. In the Saint Elias Mountains, the presence of weak sedimentary and metamorphic rocks and active uplift resulting from the collision of the Yakutat and North American tectonic plates create landslide-prone conditions. To differentiate between the typical frequency of landsliding resulting from the geologic and tectonic setting of this region, and landslide processes that may be accelerated due to changes in climate, we used Landsat imagery to create an inventory of rock avalanches in a 3700 km 2 area of the Saint Elias Mountains. During the period from 1984 to 2019, we identified 220 rock avalanches with a mean recurrence interval of 60 days. We compared our landslide inventory with a catalog of M ≥ 4 earthquakes to identify potential coseismic events, but only found three possible earthquake-triggered rock avalanches. We observed a distinct temporal cluster of 41 rock avalanches from 2013 through 2016 that correlated with above average air temperatures (including the three warmest years on record in Alaska, 2014-2016); this cluster was similar to a temporal cluster of recent rock avalanches in nearby Glacier Bay National Park and Preserve. The majority of rock avalanches initiated from bedrock ridges in probable permafrost zones, suggesting that ice loss due to permafrost degradation, as opposed to glacial thinning, could be a dominant factor contributing to rock-slope failures in the high elevation areas of the Saint Elias Mountains. Although earthquake-triggered landslides have episodically occurred in southern Alaska, evidence from our study suggests that area-normalized rates of non-coseismic rock avalanches were greater during the period from 1964 to 2019, and that the frequency of these events will continue to increase as the climate continues to warm. These findings highlight the need for hazard assessments in Alaska that address changes in landslide patterns related to climate change.

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Section: Introductionmentioning

confidence: 99%

A 36-Year Record of Rock Avalanches in the Saint Elias Mountains of Alaska, With Implications for Future Hazards

Bessette-Kirton

Coe

2020

Front. Earth Sci.

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“…These factors include soft sediments, polythermal ice conditions, abnormal geothermal heat flux, high water input and basal water pressure, glacier surging, or significant steepening in surface slope. As it has been shown that also thermal conditions can play a role in the detachments of glaciers (Gilbert et al, 2018;Jacquemart et al, 2020), we also try to evaluate permafrost conditions for each event.…”

Section: Glacier Detachment Eventsmentioning

confidence: 99%

“…This region in Alaska is home to many surging glaciers (e.g., Harrison et al, 2015; On 5 August 2013, the lower 500 m of the glacier detached, releasing 6.8-11.2 10 6 m 3 of ice and lithic material. On 31 July 530 2015, most of the remaining glacier ice (up to the drainage divide) detached, evacuating an additional 17.6-20.1 10 6 m 3 (Jacquemart et al, 2020). Both events produced runouts of over 11 km (angle of reach 6-7°), deposited vast amounts of lithic https://doi.org/10.5194/tc-2020-243 Preprint.…”

Section: Zelunglung Glacier Surge-like Instabilitiesmentioning

confidence: 99%

“…Indeed, several detachments similar to the Aru events, though smaller in magnitude, have been detected since (Falaschi et. al., 2019;Paul 2019;Jacquemart et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

“…Located in the rain shadow of the St. Elias range, the area receives on average about 350 mm of precipitation annually 526(2008 -2018). A mean annual air temperature of -14°C at the former terminus of Flat Creek glacier, ground temperature measurements, and electrical resistivity tomography surveys strongly suggest that the headwall is underlain by continuous 528 permafrost(Jacquemart et al, 2020).…”

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Sudden large-volume detachments of low-angle mountain glaciers – more frequent than thought

Kaeaeb¹,

Jacquemart²,

Gilbert³

et al. 2020

Preprint

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Abstract. 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 unknown glacier detachments have been discovered and described, and new ones occurred. In the current contribution, we compile, compare and discuss 19 actual or possible large-volume detachments of low-angle mountain glaciers at nine different sites in the Caucasus, the Pamirs, Tibet, Alaska’s St. Elias mountains, and the Southern Andes. Many of the detachments reached volumes in the order of 10–100 million m3. Commonalities and differences between the cases investigated suggest that a set of different conditions drives a transient combination of factors related to low basal friction, high driving stress, concentration of shear stress, and low resistance to exceed stability thresholds. Particularly, soft bedrocks below the detached glaciers seem to be a common condition among the observed events, as they offer smooth contact areas between the glacier and its substratum while being prone to till-strength weakening and eventually basal failure under high pore-water pressure. Surface slopes of the detached glaciers range between around 10° and 20°, possibly on the one hand low enough to enable development of thick and thus large-volume glaciers, and on the other hand steep enough to allow critical basal stresses to build up. Most of the ice-rock avalanches resulting from the detachments in this study have a particularly low angle of reach, down to around 0.1 (apparent friction angle), likely due to their high ice content and connected liquefaction potential, the ready availability of soft basal slurries and large amounts of basal water, and 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 or their geographic proximity to other surge-type glaciers suggests the glacier detachments investigated can be interpreted as end-members of the continuum of surge-like glacier instabilities. Though rare, glacier detachments appear more frequent than previously 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.

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Topographic controls on ice flow and recession for Juneau Icefield (Alaska/British Columbia)

Davies

Bendle

Carrivick

et al. 2022

Earth Surf Processes Landf

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Globally, mountain glaciers and ice caps are losing dramatic volumes of ice. The resultant sea‐level rise is dominated by contributions from Alaska. Plateau icefields may be especially sensitive to climate change due to the non‐linear controls their topography imparts on their response to climate change. However, Alaskan plateau icefields have been subject to little structural glaciological or regional geomorphological assessment, which makes the controls on their present and former mass balance difficult to ascertain. We inventoried 1050 glaciers and 368 lakes in the Juneau Icefield region for the year 2019. We found that 63 glaciers had disappeared since the 2005 inventory, with a reduction in glacier area of 422 km2 (10.0%). We also present the first structural glaciological and geomorphological map for an entire icefield in Alaska. Glaciological mapping of >20 800 features included crevasses, debris cover, foliation, ogives, medial moraines and, importantly, areas of glacier fragmentation, where glaciers either separated from tributaries via lateral recession (n = 59), or disconnected within areas of former icefalls (n = 281). Geomorphological mapping of >10 200 landforms included glacial moraines, glacial lakes, trimlines, flutes and cirques. These landforms were generated by a temperate icefield during the Little Ice Age (LIA) neoglaciation. These data demonstrate that the present‐day outlet glaciers, which have a similar thermal and ice‐flow regime, have undergone largely continuous recession since the LIA. Importantly, disconnections occurring within glaciers can separate accumulation and ablation zones, increasing rates of glacier mass loss. We show that glacier disconnections are widespread across the icefield and should be critically taken into consideration when icefield vulnerability to climate change is considered.

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What drives large-scale glacier detachments? Insights from Flat Creek glacier, St. Elias Mountains, Alaska

Cited by 41 publications

References 25 publications

A 36-Year Record of Rock Avalanches in the Saint Elias Mountains of Alaska, With Implications for Future Hazards

A 36-Year Record of Rock Avalanches in the Saint Elias Mountains of Alaska, With Implications for Future Hazards

Sudden large-volume detachments of low-angle mountain glaciers – more frequent than thought

Topographic controls on ice flow and recession for Juneau Icefield (Alaska/British Columbia)

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