Transience in cascading paraglacial systems

Knight, Jasper; Harrison, Stephan

doi:10.1002/ldr.2994

Cited by 47 publications

(34 citation statements)

References 111 publications

(146 reference statements)

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“…In Kongsfjorden, the reversal of the coastal evolution trend since 1990, illustrated by an increase of the erosion rate and a decrease of the progradation rate, highlight a drying up of the sediment input and announce the end of the transitional paraglacial period in the coastal dynamic of the Brøgger peninsula (Figure ). This study shows also the importance of transient properties of paraglacial systems (Knight & Harrison, ).…”

Section: Discussionsupporting

confidence: 60%

Paraglacial coasts responses to glacier retreat and associated shifts in river floodplains over decadal timescales (1966–2016), Kongsfjorden, Svalbard

et al. 2018

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The aim of this paper is to quantify and map the impact of the post-Little Ice Age climate change on the coastal evolution on three glacier catchments in the Kongsfjorden area in Svalbard. Climatic data at Ny-Ålesund indicate an increase in the annual mean air temperature of +4°C from 1969 to 2016 and an increase in precipitation. On the northern coast of the Brøgger Peninsula, the Austre Lovénbreen, Midtre Lovénbreen, and Vestre Lovénbreen glaciers have experienced a net retreat in response to changing meteorological conditions. Because of this retreat, the glaciers have disclosed a large area of 7 km 2 composed of terrigenous sediments. These sediments are transported by runoff and created coastal sandur deltas. Channel network behavior has been studied using the computation of the active floodplain width by photointerpretation, which decreased in average from 1966 to 2010. This demonstrated a contraction of the active braided belt and a decrease in the number of braided channels.A photointerpretation analysis combined with acquisition of dGPS data during field work shows a mean shoreline progradation of +0.16 m a −1 from 1966 to 2016, with a maximal advance of +82 m seaward. Since 1966, coastal progradation has decreased in time with higher mean values at the beginning of the studied period and an erosional trend from 1990. The sublittoral area was studied using analog side scan sonar in 2009, 2011, 2012, and 2017. Three prodeltas were identified and underwent a huge extension from 2009 to 2017. In the light of this knowledge, our main conclusion is that, by retreating, glaciers have an impact on the sediment availability and on the capacity of the fluvial system to effectively transport sediment to the shoreline. These two factors control the overall coastal evolution by regulating the sediment supply to the coastal area. The coastal zones that were fed with sediments by runoff have experienced a coastal progradation, and those that lost this supply have undergone a coastal recession. Due to the contraction of proglacial floodplains, current progradation concerns restricted coastal areas.

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Section: Discussionsupporting

confidence: 60%

Paraglacial coasts responses to glacier retreat and associated shifts in river floodplains over decadal timescales (1966–2016), Kongsfjorden, Svalbard

et al. 2018

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“…The sudden shift in regime from glacial to ‘paraglacial’, i.e. those processes, landforms and sediments conditioned by glaciation, has been hypothesized to result in elevated sediment yields from landscapes undergoing and following rapid deglaciation (Church and Ryder, 1972; Harbor and Warburton, 1993; Ballantyne, 2002; Knight and Harrison, 2014, 2018), and has been demonstrated to produce significantly higher yields than from denudation of landscapes with no history of glaciation (Church and Ryder, 1972; Church and Slaymaker, 1989; Hallet and others, 1996; Ballantyne, 2002; Koppes and Montgomery, 2009).…”

Section: Introductionmentioning

confidence: 99%

“…Sediment yields to the glacier forefield are presumed to decrease as the paraglacial period progresses, but intermittent, episodic pulses of sediment can temporarily increase sediment fluxes due to transient processes which increase sediment connectivity (Ballantyne, 2002; Meigs and others, 2006; Heckmann and others, 2012; Lane and others, 2017; Knight and Harrison, 2018). These pulses of sediment can be sourced from stochastic processes, such as the triggering of a landslide due to changes in internal stresses of bedrock and debuttressing of valley walls as ice thins and retreats (e.g.…”

Section: Introductionmentioning

confidence: 99%

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A comparison of glacial and paraglacial denudation responses to rapid glacial retreat

Williams

Koppes

2019

Ann. Glaciol.

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Glacier thinning and retreat drives initial acceleration of glacier sliding and erosion, de-buttressing of steep valley walls, and destabilization of ice-marginal deposits and bedrock, which can lead to massive rock avalanching and accelerated incision of tributary watersheds. A compelling example of these changes occurred in Taan Fjord in SE Alaska due to the rapid thinning and retreat of Tyndall Glacier over the past half century. Increased glacier sliding speeds led to both increased rates of subglacial erosion and the evacuation of subglacially stored sediments into the proglacial basins. The shrinking glacier also exposed proglacial tributary watersheds to rapid incision and denudation driven by >350 m of baselevel fall in a few decades. Moreover, in October 2015 a large tsunamigenic landslide occurred at the terminus of Tyndall Glacier, largely due to thinning exposing oversteepened, unstable slopes. Sediment yields from the glacier, the landslide and the tributary watersheds, measured from surveys of the sediments in the fjord collected in 1999 and 2016, are compared to ongoing changes in glacier and fjord geometry to investigate the magnitude of glacial and paraglacial denudation in Taan Fjord during retreat. In the last 50 years, sediment yields from the glacier and non-glacial tributaries kept pace with the rapid rate of retreat, and were on par with each other. Notably, basin-averaged erosion rates from the paraglacial landscape were twice that from the glacier, averaging 58 ± 9 and 26 ± 5 mm a−1, respectively. The sharp increases in sediment yields during retreat observed from both the glacier and the adjacent watersheds, including the landslide, highlight the rapid evolution of landscapes undergoing glacier shrinkage.

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“…Kellerer‐Pirklbauer and Kaufmann () examined small glaciated LIA cirques in the Austrian Alps highlighting the intensity of cryogenic processes during the transition between glacial and periglacial environments; similar to the Iberian Peninsula, they observed how buried glacier remnants generate permafrost aggradation on the debris deposits (i.e., active layer) covering and preserving these buried ice bodies, and being also affected by creep processes. Enhanced slope instability in the Alps as well as in other glaciated midlatitude mountain environments during the LIA is not only related to climate warming but also to intense paraglacial responses adjusting to the new geomorphological setting following glacier retreat (Knight & Harrison, ).…”

Section: The Iberian Post‐lia Paraglacial Landsystemsmentioning

confidence: 99%

Post‐little ice age paraglacial processes and landforms in the high Iberian mountains: A review

et al. 2018

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Three Iberian mountain ranges encompassed glaciers during the Little Ice Age (LIA):the Pyrenees, Cantabrian Mountains, and Sierra Nevada. The gradual warming trend initiated during the second half of the 19th century promoted the progressive shrinking of these glaciers, which completely melted during the first half of the 20th century in the Cantabrian mountains and Sierra Nevada and reduced by 80% of their LIA extent in the Pyrenees. In these formerly glaciated environments, the transition between glacial and periglacial conditions results in an accelerated paraglacial readjustment, with very active geomorphic processes. Cirque walls generate a large amount of sediments through rock-falls and slides. LIA moraines, devoid of vegetation and composed of highly unstable sediments, are being intensely mobilized by slope processes. Inside the moraines, the shrinking of LIA glaciers favoured the development of buried ice patches, with permafrost-related landforms, small periglacial features generated by solifluction, and cryoturbation processes and remarkable hydrological changes. Present-day morphodynamics is mostly related to seasonal frost, though patches of permafrost have formed in contact with the buried ice, undergoing a process of degradation because it is not balanced with present-day climate. This is reflected in the occurrence of multiple collapses and subsidence of the debris cover where the frozen bodies sit. Next to the small glaciated environments in the highest Pyrenean massifs, there is a permafrost belt undergoing also rapid geomorphic changes. Based on the observed processes, we discuss spatio-temporal patterns of paraglacial readjustment in Iberian mountains and compare it with other midlatitude mountain environments.

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Transience in cascading paraglacial systems

Cited by 47 publications

References 111 publications

Paraglacial coasts responses to glacier retreat and associated shifts in river floodplains over decadal timescales (1966–2016), Kongsfjorden, Svalbard

Paraglacial coasts responses to glacier retreat and associated shifts in river floodplains over decadal timescales (1966–2016), Kongsfjorden, Svalbard

A comparison of glacial and paraglacial denudation responses to rapid glacial retreat

Post‐little ice age paraglacial processes and landforms in the high Iberian mountains: A review

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