Effects of rock avalanches on glacier behaviour and moraine formation

Reznichenko, Natalya; Davies, Tim; Alexander, David

doi:10.1016/j.geomorph.2011.05.019

Cited by 92 publications

(78 citation statements)

References 62 publications

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“…The effect of temporal and spatial changes in debris deposition must be addressed through both empirical and theoretical approaches. Isolated, large landslides have been shown to suppress melt rates, change glacier surface slopes and perturb glacier surface velocity fields (Gardner and Hewitt, 1990;Reznichenko et al, 2011;Shugar et al, 2012). If debris inputs are allowed to vary in space and time, a complex glacier length history will likely result even with a steady climate.…”

Section: Potential Model Improvements and Future Researchmentioning

confidence: 99%

Modeling debris-covered glaciers: response to steady debris deposition

2016

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Abstract. Debris-covered glaciers are common in rapidly eroding alpine landscapes. When thicker than a few centimeters, surface debris suppresses melt rates. If continuous debris cover is present, ablation rates can be significantly reduced leading to increases in glacier length. In order to quantify feedbacks in the debris-glacier-climate system, we developed a 2-D long-valley numerical glacier model that includes englacial and supraglacial debris advection. We ran 120 simulations on a linear bed profile in which a hypothetical steady state debris-free glacier responds to a step increase of surface debris deposition. Simulated glaciers advance to steady states in which ice accumulation equals ice ablation, and debris input equals debris loss from the glacier terminus. Our model and parameter selections can produce 2-fold increases in glacier length. Debris flux onto the glacier and the relationship between debris thickness and melt rate strongly control glacier length. Debris deposited near the equilibriumline altitude, where ice discharge is high, results in the greatest glacier extension when other debris-related variables are held constant. Debris deposited near the equilibrium-line altitude re-emerges high in the ablation zone and therefore impacts melt rate over a greater fraction of the glacier surface. Continuous debris cover reduces ice discharge gradients, ice thickness gradients, and velocity gradients relative to initial debris-free glaciers. Debris-forced glacier extension decreases the ratio of accumulation zone to total glacier area (AAR). Our simulations reproduce the "general trends" between debris cover, AARs, and glacier surface velocity patterns from modern debris-covered glaciers. We provide a quantitative, theoretical foundation to interpret the effect of debris cover on the moraine record, and to assess the effects of climate change on debris-covered glaciers.

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Section: Potential Model Improvements and Future Researchmentioning

confidence: 99%

Modeling debris-covered glaciers: response to steady debris deposition

2016

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“…In combination with a coupled glacier-outwash system (Benn et al, 2003), this efficient debris throughput is unlikely to lead to the development of large areas of debris-covered, stagnant ice or substantial RSF-related latero-frontal moraine arcs (cf. Reznichenko, Davies, & Alexander, 2011, 2012a, 2012b around the margins of a receding active temperate valley glacier.…”

Section: Morsárjökull and Its Historical Activitymentioning

confidence: 99%

The glaciated valley landsystem of Morsárjökull, southeast Iceland

2017

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“…This accumulating debris serves as a source of material for moraine construction (Reznichenko et al, 2011(Reznichenko et al, , 2012 but can also insulate a glacier and dampen its response to climate (Kirkbride and Warren, 1999;Anderson, 2000;Scherler et al, 2011) and can even trigger phases of glacier advance (see Tovar et al, 2008;Hewitt, 2009). Where steep slopes overlook a glacier's surface, debris accumulation can be considerable, and glaciers can persist far below the regional climatic ELA (Scherler et al, 2011) -with a direct impact on where moraines are deposited.…”

Section: Accumulation Area Topography and Controls On Debris Supplymentioning

confidence: 99%

A review of topographic controls on moraine distribution

2014

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Ice-marginal moraines are often used to reconstruct the dimensions of former ice masses, which are then used as proxies for palaeoclimate. This approach relies on the assumption that the distribution of moraines in the modern landscape is an accurate reflection of former ice margin positions during climatically controlled periods of ice margin stability. However, the validity of this assumption is open to question, as a number of additional, nonclimatic factors are known to influence moraine distribution. This review considers the role played by topography in this process, with specific focus on moraine formation, preservation, and ease of identification (topoclimatic controls are not considered). Published literature indicates that the importance of topography in regulating moraine distribution varies spatially, temporally, and as a function of the ice mass type responsible for moraine deposition. In particular, in the case of ice sheets and ice caps ( > 1000 km 2 ), one potentially important topographic control on where in a landscape moraines are deposited is erosional feedback, whereby subglacial erosion causes ice masses to become less extensive over successive glacial cycles. For the marine-terminating outlets of such ice masses, fjord geometry also exerts a strong control on where moraines are deposited, promoting their deposition in proximity to valley narrowings, bends, bifurcations, where basins are shallow, and/or in the vicinity of topographic bumps. Moraines formed at the margins of ice sheets and ice caps are likely to be large and readily identifiable in the modern landscape. In the case of icefields and valley glaciers (10-1000 km 2 ), erosional feedback may well play some role in regulating where moraines are deposited, but other factors, including variations in accumulation area topography and the propensity for moraines to form at topographic pinning points, are also likely to be important. This is particularly relevant where land-terminating glaciers extend into piedmont zones (unconfined plains, adjacent to mountain ranges) where large and readily identifiable moraines can be deposited. In the case of cirque glaciers (< 10 km 2 ), erosional feedback is less important, but factors such as topographic controls on the accumulation of redistributed snow and ice and the availability of surface debris, regulate glacier dimensions and thereby determine where moraines are deposited. In such cases, moraines are likely to be small and particularly susceptible to post-depositional modification, sometimes making them difficult to identify in the modern landscape. Based on this review, we suggest that, despite often being difficult to identify, quantify, and mitigate, topographic controls on moraine distribution should be explicitly considered when reconstructing the dimensions of palaeoglaciers and that moraines should be judiciously chosen before being used as indirect proxies for palaeoclimate (i.e., palaeoclimatic inferences should only be drawn from moraines when topographic controls on mora...

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Effects of rock avalanches on glacier behaviour and moraine formation

Cited by 92 publications

References 62 publications

Modeling debris-covered glaciers: response to steady debris deposition

Modeling debris-covered glaciers: response to steady debris deposition

The glaciated valley landsystem of Morsárjökull, southeast Iceland

A review of topographic controls on moraine distribution

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