Regional and Annual Variability in Subglacial Sediment Transport by Water for Two Glaciers in the Swiss Alps

Delaney, Ian; Bauder, Andreas; Werder, Mauro; Farinotti, Daniel

doi:10.3389/feart.2018.00175

Cited by 37 publications

(86 citation statements)

References 67 publications

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“…At Gornergletscher, by contrast, processes captured by the till model, including sediment connectivity and bedrock erosion, are of primary importance compared to the water's sediment transport capacity, largely controlled by Δ t . Similar to subglacial sediment dynamics (Delaney, Bauder, Werder, et al, ), the relative importance of tuning parameters can vary substantially from glacier to glacier (Table and Figure , orange squares). High variability can particularly be noted for f sl , suggesting that differences in bedrock erosion are a primary factor for the variability in subglacial sediments transport.…”

Section: Resultsmentioning

confidence: 93%

“…The model results support the observation that till is quickly evacuated after its creation when sufficient melt is present (Herman et al, ; Riihimaki et al, ) and, thus, that a high sediment connectivity persists (e.g., Bracken et al, ; Mao et al, ). Additionally, it is observed that coincident variations in sediment and water discharge are limited to periods during which till storage is not exhausted (Delaney, Bauder, Werder, et al, ).…”

Section: Model Response In Idealized Test Casesmentioning

confidence: 99%

“…To put the model performance into context, the results were compared to the empirical relationship between sediment and water discharge proposed by Delaney, Bauder, Werder, et al (). The relation is of the form

\overset{Q_{s}^{0}}{true} = false(a + b t false) {((), \overset{Q_{w}^{0}}{true})}^{c} \overset{Q_{w}^{0}}{true} ρ_{normals}^{- 1},

where a , b , and c are empirical coefficients determined by minimizing ERR k (equation ) and t is time since 10 May of the considered year.…”

Section: Comparison With Real‐world Observationsmentioning

confidence: 99%

“…The relation is of the form

\overset{Q_{s}^{0}}{true} = false(a + b t false) {((), \overset{Q_{w}^{0}}{true})}^{c} \overset{Q_{w}^{0}}{true} ρ_{normals}^{- 1},

where a , b , and c are empirical coefficients determined by minimizing ERR k (equation ) and t is time since 10 May of the considered year. The term

false(a + b t false) {((), \overset{Q_{w}^{0}}{true})}^{c}

captures sediment concentration, where a and b describe how sediment connectivity evolves through the season, and c describes the sensitivity of the till mobilization to water discharge Delaney, Bauder, Werder, et al (). Values of c both above and below 1 have been found by Delaney, Bauder, Werder, et al (), suggesting that Q w can have either an amplified or muted effect on sediment discharge.…”

Section: Comparison With Real‐world Observationsmentioning

confidence: 99%

“…The term

false(a + b t false) {((), \overset{Q_{w}^{0}}{true})}^{c}

Section: Comparison With Real‐world Observationsmentioning

confidence: 99%

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A Numerical Model for Fluvial Transport of Subglacial Sediment

2019

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Sediment discharge from glaciers impacts downstream aquatic habitats, hydropower operations, and river infrastructure. Since discharge of subglacial sediment will evolve in response to glacier retreat, estimating future subglacial sediment dynamics is of great relevance. To develop tools and methods to better constrain the responsible processes, we present a till dynamics model that accounts for limited sediment access coupled to a subglacial hydrology model to describe the evolution of a subglacial till layer over a glacier's longitudinal profile in one dimension. Synthetic simulations examining the effects of changing hydrology highlight the importance of properly constraining both the erosion of underlying bedrock and the subglacial sediment connectivity. This is because changes in hydrology alter the timing of peak sediment discharge but only marginally affect total sediment discharge once the subglacial sediment reservoir is exhausted. Model simulations for real‐world glaciers yield insights into the distribution of sediment along the glacier bed, including locations where sediments are deposited or exhausted. Comparison between model results and field data shows that total and peak sediment discharge, as well as interannual variability, can be captured with acceptable skill for periods ranging from hours to decades. The results from this model show that modeling subglacial sediment transport on decadal to subdaily scales is possible but requires processes such as bedrock erosion and sediment connectivity to be considered.

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Section: Resultsmentioning

confidence: 93%

Section: Model Response In Idealized Test Casesmentioning

confidence: 99%

\overset{Q_{s}^{0}}{true} = false(a + b t false) {((), \overset{Q_{w}^{0}}{true})}^{c} \overset{Q_{w}^{0}}{true} ρ_{normals}^{- 1},

where a , b , and c are empirical coefficients determined by minimizing ERR k (equation ) and t is time since 10 May of the considered year.…”

Section: Comparison With Real‐world Observationsmentioning

confidence: 99%

“…The relation is of the form

\overset{Q_{s}^{0}}{true} = false(a + b t false) {((), \overset{Q_{w}^{0}}{true})}^{c} \overset{Q_{w}^{0}}{true} ρ_{normals}^{- 1},

where a , b , and c are empirical coefficients determined by minimizing ERR k (equation ) and t is time since 10 May of the considered year. The term

false(a + b t false) {((), \overset{Q_{w}^{0}}{true})}^{c}

Section: Comparison With Real‐world Observationsmentioning

confidence: 99%

“…The term

false(a + b t false) {((), \overset{Q_{w}^{0}}{true})}^{c}

Section: Comparison With Real‐world Observationsmentioning

confidence: 99%

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A Numerical Model for Fluvial Transport of Subglacial Sediment

2019

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The hydrology of glacier‐bed overdeepenings: Sediment transport mechanics, drainage system morphology, and geomorphological implications

Swift

Tallentire

Farinotti

et al. 2021

Earth Surf Processes Landf

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Evacuation of basal sediment by subglacial drainage is an important mediator of rates of glacial erosion and glacier flow. Glacial erosion patterns can produce closed basins (i.e., overdeepenings) in glacier beds, thereby introducing adverse bed gradients that are hypothesized to reduce drainage system efficiency and thus favour basal sediment accumulation. To establish how the presence of a terminal overdeepening might mediate seasonal drainage system evolution and glacial sediment export, we measured suspended sediment transport from Findelengletscher, Switzerland during late August and early September 2016. Analyses of these data demonstrate poor hydraulic efficiency of drainage pathways in the terminus region but high sediment availability. Specifically, the rate of increase of sediment concentration with discharge was found to be significantly lower than that anticipated if channelized flow paths were present. Sediment availability to these flow paths was also higher than would be anticipated for discrete bedrock-floored subglacial channels. Our findings indicate that subglacial drainage in the terminal region of Findelengletscher is dominated by distributed flow where entrainment capacity increases only marginally with discharge, but flow has extensive access to an abundant sediment store. This high availability maintains sediment connectivity between the glacial and proglacial realm and means daily sediment yield is unusually high relative to yields exhibited by similar Alpine glaciers. We present a conceptual model illustrating the potential influence of ice-bed morphology on subglacial drainage evolution and sediment evacuation mechanics, patterns and yields, and recommend that bed morphology should be an explicit consideration when monitoring and evaluating glaciated basin sediment export rates.

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Fluvial suspended sediment transfer and lacustrine sedimentation of recent flood turbidites in proglacial Eklutna Lake, western Chugach Mountains, Alaska

Schiefer

Geck

Ostman

et al. 2021

Hydrological Processes

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Suspended sediment delivery and deposition in proglacial lakes is generally sensitive to a wide range of hydrometeorologic and geomorphic controls. High discharge conditions are of particular importance in many glaciolacustrine records, with individual floods potentially recorded as distinctive turbidites. We used an extensive network of surface sediment cores and hydroclimatic monitoring data to analyse recent flood turbidites and associated sediment transfer controls over instrumental periods at Eklutna Lake, western Chugach Mountains, Alaska. Close to a decade of fluvial data from primary catchment tributaries show a dominating influence of discharge on sediment delivery, with various interconnections with other related hydroclimatic controls. Multivariate fluvial models highlight and help quantify some complexities in sediment transfer, including intra-annual variations, meteorological controls, and the influence of subcatchment glacierization. Sediments deposited in Eklutna Lake during the last half century are discontinuously varved and contain multiple distinctive turbidites. Over a 30-year period of stratigraphic calibration, we correlate the four thickest flood turbidites (1989, 1995, 2006, and 2012) to specific regional storms. The studied turbidites correlate with late-summer and early-autumn rainstorms with a magnitude of relatively instantaneous sedimentation 3-15 times greater than annual background accumulation. Our network of sediment core data captured the broad extent and sediment variability among the study turbidites and background sediment yield. Within-lake spatial modelling of deposition quantifies variable rates of downlake thinning and sediment focusing effects, and highlights especially large differences between the thickest flood turbidites and background sedimentation. This we primarily relate to strongly contrasting dispersion processes controlled by inflow current strength and turbidity. Sediment delivery is of interest for this catchment because of reservoir and water supply operations. Furthermore, although smaller floods may not be consistently represented, the lake likely contains a valuable proxy record of regional flooding proximal to major population centers of south-central Alaska including Anchorage.

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Regional and Annual Variability in Subglacial Sediment Transport by Water for Two Glaciers in the Swiss Alps

Cited by 37 publications

References 67 publications

A Numerical Model for Fluvial Transport of Subglacial Sediment

A Numerical Model for Fluvial Transport of Subglacial Sediment

The hydrology of glacier‐bed overdeepenings: Sediment transport mechanics, drainage system morphology, and geomorphological implications

Fluvial suspended sediment transfer and lacustrine sedimentation of recent flood turbidites in proglacial Eklutna Lake, western Chugach Mountains, Alaska

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