Advances in understanding subglacial meltwater drainage from past ice sheets

Simkins, Lauren M.; Greenwood, Sarah L.; Winsborrow, Monica; Bjarnadóttir, Lilja Rún; Lepp, Allison

doi:10.31223/x5ss8h

Cited by 2 publications

(1 citation statement)

References 53 publications

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“…Meltwater landforms preserved in glaciated landscapes allow the properties of subglacial meltwater drainage to be reconstructed, typically over decadal to millennial time‐scales and spatially over hundreds of kilometres (Burke et al, 2012a; Jennings et al, 2006; Ravier et al, 2022; Storrar et al, 2014). Such landforms therefore have enormous potential for informing our understanding of present‐day subglacial hydrological configurations and processes (Davison et al, 2019; Greenwood et al, 2016; Simkins et al, 2023). With the advent of high‐resolution digital elevation models (DEMs), one of the most obvious geomorphological expressions of former subglacial drainage systems is subglacial meltwater corridors (SMCs).…”

Section: Introductionmentioning

confidence: 99%

Conceptual model for the formation of bedforms along subglacial meltwater corridors (SMCs) by variable ice‐water‐bed interactions

Vérité,

Livingstone,

Ravier

et al. 2023

Earth Surf Processes Landf

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Subglacial meltwater landforms found on palaeo‐ice sheet beds allow the properties of meltwater drainage to be reconstructed, informing our understanding of modern‐day subglacial hydrological processes. In northern Canada and Fennoscandia, subglacial meltwater landforms are largely organized into continental‐scale networks of subglacial meltwater corridors (SMCs), interpreted as the relics of subglacial drainage systems undergoing variations in meltwater input, effective pressure and drainage efficiency. We review the current state of knowledge of bedforms (hummocks, ridges, murtoos, ribbed bedforms) and associated landforms (channels, eskers) described along SMCs and use selected high‐resolution DEMs in Canada and Fennoscandia to complete the bedform catalogue and categorize their characteristics, patterning and spatial distributions. We synthesize the diversity of bedform and formation processes occurring along subglacial drainage routes in a conceptual model invoking spatiotemporal changes in hydraulic connectivity, basal meltwater pressure and ice‐bed coupling, which influences the evolution of subglacial processes (bed deformation, erosion, deposition) along subglacial drainage systems. When the hydraulic capacity of the subglacial drainage system is overwhelmed glaciofluvial erosion and deposition will dominate in the SMC, resulting in tracts of hummocks and ridges arising from both fragmentation of underlying pre‐existing bedforms and downstream deposition of sediments in basal cavities and crevasses. Re‐coupling of ice with the bed, when meltwater supply decreases, facilitates deformation, transforming existing and producing new bedforms concomitant with the wider subglacial bedform imprint. We finally establish a range of future research perspectives to improve understanding of subglacial hydrology, geomorphic processes and bedform diversity along SMCs. These perspectives include the new acquisition of remote‐sensing and field‐based sedimentological and geomorphological data, a better connection between the interpreted subglacial drainage configurations down corridors and the mathematical treatments studying their stability, and the quantification of the scaling, distribution and evolution of the hydraulically connected drainage system beneath present‐day ice masses to test our bedform‐related conceptual model.

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Section: Introductionmentioning

confidence: 99%

Conceptual model for the formation of bedforms along subglacial meltwater corridors (SMCs) by variable ice‐water‐bed interactions

Vérité,

Livingstone,

Ravier

et al. 2023

Earth Surf Processes Landf

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Insights into glacial processes from micromorphology of silt-sized sediment

Lepp,

Miller,

Anderson

et al. 2024

The Cryosphere

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Abstract. Silt-rich meltwater plume deposits (MPDs) analyzed from marine sediment cores have elucidated relationships that are clearly connected, yet difficult to constrain, between subglacial hydrology, ice-marginal landforms, and grounding-zone retreat patterns for several glacial catchments. Few attempts have been made to infer details of subglacial hydrology, such as flow regime, geometry of drainage pathways, and mode(s) of sediment transport through time, from grain-scale characteristics of MPDs. Using sediment samples from MPD, till, and grounding-zone proximal diamicton collected offshore of six modern and relict glacial catchments in both hemispheres, we examine grain shape distributions and microtextures (collectively, grain micromorphology) of the silt fraction to explore whether grains are measurably altered from their subglacial sources via meltwater action. We find that 75 % of all imaged grains (n = 9400) can be described by 25 % of the full range of measured shape morphometrics, indicating grain shape homogenization through widespread and efficient abrasive processes in subglacial environments. Although silt grains from MPDs exhibit edge rounding more often than silt grains from tills, grain surface textures indicative of fluvial transport (e.g., v-shaped percussions) occur in only a modest number of grains. Furthermore, MPD grain surfaces retain several textures consistent with transport beneath glacial ice (e.g., straight or arcuate steps, (sub)linear fractures) in comparable abundances to till grains. Significant grain shape alteration in MPDs compared to their till sources is observed in sediments from glacial regions where (1) high-magnitude, potentially catastrophic meltwater drainage events are inferred from marine sediment records and (2) submarine landforms suggest supraglacial melt contributed to the subglacial hydrological budget. This implies that quantifiable grain shape alteration in MPDs could reflect a combination of high-energy flow of subglacial meltwater, persistent sediment entrainment, and/or long sediment transport distances through subglacial drainage pathways. Integrating grain micromorphology into analysis of MPDs in site-specific studies could therefore aid in distinguishing periods of persistent, well-connected subglacial discharge from periods of sluggish or disorganized drainage. In the wider context of deglacial marine sedimentary and bathymetric records, a grain micromorphological approach may bolster our ability to characterize ice response to subglacial meltwater transmission through time. This work additionally demonstrates that glacial and fluvial surface textures are retained on silt-sized quartz grains in adequate amounts for microtexture analysis, which has heretofore been conducted exclusively on the sand fraction. Therefore, grain microtextures can be examined on silt-rich glaciogenic deposits that contain little to no sand as a means to evaluate sediment transport processes.

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Advances in understanding subglacial meltwater drainage from past ice sheets

Cited by 2 publications

References 53 publications

Conceptual model for the formation of bedforms along subglacial meltwater corridors (SMCs) by variable ice‐water‐bed interactions

Conceptual model for the formation of bedforms along subglacial meltwater corridors (SMCs) by variable ice‐water‐bed interactions

Insights into glacial processes from micromorphology of silt-sized sediment

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