Proglacial erosion rates and processes in a glacierized catchment in the Swiss Alps

Abstract

In the Swiss Alps, climatic changes have not only caused glacier retreat, but also likely increased sedimentation downstream of glaciers. This material either originates from below the glacier or from periglacial environments, which are exposed as glaciers retreat, and often consist of easily erodible sediment. Griesgletscher's catchment in the Swiss Alps was examined to quantify erosion in the proglacial area, possible hydrological drivers and contributions of the sub-and periglacial sources. Digital elevation models, created from annual aerial photographs, were subtracted to determine annual volume changes in the proglacial area from 1986 to 2014. These data show a strong increase in proglacial erosion in the decade prior to 2012, coincident with increasing proglacial area size. However, examination of the gradient between discharge and sediment evacuation, and modeled sediment transport, could suggest that the proglacial area began to stabilize and sediment supply is limited. The large influx of sediment into the proglacial reservoir, which is roughly 2.5 times greater than the amount of sediment eroded from the proglacial area, demonstrates the importance of subglacial erosion to the catchment's sediment budget. Although far more sediment originates subglacially, erosion rates in the proglacial area are over 50 times greater than the rest of the catchment. In turn, both sub-and periglacial processes, in addition to constraining sediment supply, must be considered for assessing future sediment dynamics as glacier area shrinks and proglacial areas grow.

Proglacial sediment dynamics from daily to seasonal scales in a glaciated Alpine catchment (Bossons glacier, Mont Blanc massif, France)

“…Comparing proximal and distal sediment concentrations within the Glacier Noir catchment (Massif des Ecrins, France), Stott and Mount (2007) demonstrated an 87% short-term deposit of the total load within the sandur. Using photogrammetric and bathymetric data, Delaney et al (2017) inferred that at least 72% of the sediment deposited in a dammed lake downstream from Griesgletscher (Switzerland) transited through its subglacial drainage system. Using photogrammetric and bathymetric data, Delaney et al (2017) inferred that at least 72% of the sediment deposited in a dammed lake downstream from Griesgletscher (Switzerland) transited through its subglacial drainage system.…”

“…An open research question seems now to quantify the connections between sediment buffers in sandurs (e.g., this study) or on slopes (e.g., Lane et al, 2017), connectivity (e.g., Micheletti et al, 2015), detailed sediment budgets at seasonal (e.g., Leggat et al, 2015) or pluriannual scales (e.g., Delaney et al, 2017), and detailed driver analyses in terms of meteorological conditions (e.g., Mao and Carrillo, 2016). Unravelling such connections should quantify processes controlling sediment buffer mechanisms in proglacial areas from the daily to decennial scales, the latter being relevant for extreme events.…”

“…According to the paraglacial concept, present-day proglacial areas could generate high sediment exports as sediments stored beneath glaciers or within moraines are transferred downstream (e.g., Gurnell et al, 2000). Proglacial zones are already known to react very dynamically to transient events as well as to variations in meltwater runoff, glacial terminus position and sediment supply (e.g., Staines et al, 2014;Micheletti et al, 2015;Delaney et al, 2017). Consequently, quantifying the change in sediment export from proglacial areas provides useful insights for understanding climate change implications for mass transfer from uplands to lowlands (e.g., Knight and Harrison, 2014;Heckmann et al, 2015) and for modelling changes in relief over geological time (e.g., Herman and Braun, 2008).…”

A Numerical Model for Fluvial Transport of Subglacial Sediment

“…These sediments can affect hydropower operations through turbine abrasion and reservoir infill (e.g., Anselmetti et al, 2007;Ehrbar et al, 2018;Thapa et al, 2005), as well as downstream ecosystems (e.g., Brown et al, 2007;Sigler et al, 2002) and infrastructure (e.g., Lancaster et al, 2012). Glacial sediments originate from either the subglacial or the periglacial environment (Delaney, Bauder, Huss, et al, 2018;Guillon et al, 2015). Periglacial environments often comprise loose, unconsolidated material exposed by glacier retreat (e.g., Church & Ryder, 1972;Warburton, 1990), but these environments can stabilize relatively quickly (Ballantyne, 2002;Lane et al, 2017).…”

“…Periglacial environments often comprise loose, unconsolidated material exposed by glacier retreat (e.g., Church & Ryder, 1972;Warburton, 1990), but these environments can stabilize relatively quickly (Ballantyne, 2002;Lane et al, 2017). Larger amounts of sediment, instead, typically originate subglacially, especially in highly glacierized catchments (e.g., Guillon et al, 2015;Delaney, Bauder, Huss, et al, 2018).…”