Groundwater Flow Under the Margin of the Last Scandinavian Ice Sheet Around the EckernföRde Bay, Northwest Germany

Marczinek, Silke; Piotrowski, Jan A.

doi:10.1002/9780470750636.ch10

Cited by 6 publications

(7 citation statements)

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“…Connections between ice stream activity and subglacial hydrology are supported by the occurrence of geomorphic markers of meltwater drainage on ancient ice stream beds (e.g. meltwater channels, tunnel valleys, eskers) (Patterson, 1997;Margold et al, 2015;. Among these markers, tunnel valleys deserve specific attention because they have high discharge capacities and, as such, may be major contributors to the release of meltwater and sediment to the ocean and may promote ice sheet stability by reducing the lubricating effect of high basal water pressure.…”

Section: Introductionmentioning

confidence: 99%

Modelled subglacial floods and tunnel valleys control the life cycle of transitory ice streams

et al. 2018

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Abstract. Ice streams are corridors of fast-flowing ice that control mass transfers from continental ice sheets to oceans. Their flow speeds are known to accelerate and decelerate, their activity can switch on and off, and even their locations can shift entirely. Our analogue physical experiments reveal that a life cycle incorporating evolving subglacial meltwater routing and bed erosion can govern this complex transitory behaviour. The modelled ice streams switch on and accelerate when subglacial water pockets drain as marginal outburst floods (basal decoupling). Then they decelerate when the lubricating water drainage system spontaneously organizes itself into channels that create tunnel valleys (partial basal recoupling). The ice streams surge or jump in location when these water drainage systems maintain low discharge but they ultimately switch off when tunnel valleys have expanded to develop efficient drainage systems. Beyond reconciling previously disconnected observations of modern and ancient ice streams into a single life cycle, the modelling suggests that tunnel valley development may be crucial in stabilizing portions of ice sheets during periods of climate change.

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Section: Introductionmentioning

confidence: 99%

Modelled subglacial floods and tunnel valleys control the life cycle of transitory ice streams

et al. 2018

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“…subglacial tunnel valleys have also been hypothesized to exist on Mars [Kargel and Strom, 1992;Head and Pratt, 2001;Carr and Head, 2003;Guidat et al, 2015;Souček et al, 2015]. The development of tunnel valleys has strong glaciodynamic implications, as their formation may secure the stability of ice sheets by reducing water pressures at the ice/bed interface, thereby preventing catastrophic surges and ice sheet collapses [Marczinek and Piotrowski, 2006]. There is still no consensus, however, on the formation processes of tunnel valleys because the involved mechanisms are specific to the substratum configuration, the subglacial topography, the meltwater production rates, and the drainage characteristics [Boulton and Hindmarsh, 1987;Piotrowski, 1994Piotrowski, , 1997Shaw, 2002;Praeg, 2003;Janszen et al, 2012;Ravier et al, 2014Ravier et al, , 2015.…”

Section: Introductionmentioning

confidence: 99%

Experimental modeling of pressurized subglacial water flow: Implications for tunnel valley formation

et al. 2016

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Tunnel valleys are elongated hollows commonly found in formerly glaciated areas and interpreted as resulting from subglacial meltwater erosion beneath ice sheets. Over the past two decades, the number of studies of terrestrial tunnel valleys has continuously increased, and their existence has been hypothesized also on Mars, but their formation mechanisms remain poorly understood. We introduce here an innovative experimental approach to examine erosion by circulation of pressurized meltwater within the substratum and at the ice/substratum interface. We used a permeable substratum (sand) partially covered by a viscous, impermeable, and transparent cap (silicon putty), below which we applied a central injection of pure water. Low water pressures led to groundwater circulation in the substratum only, while water pressures exceeding a threshold that is larger than the sum of the glaciostatic and lithostatic pressures led to additional water circulation and formation of drainage landforms at the cap/substratum interface. The formation of these drainage landforms was monitored through time, and their shapes were analyzed from digital elevation models obtained by stereo-photogrammetry. The experimental landforms include valleys that are similar to natural tunnel valleys in their spatial organization and in a number of diagnostic morphological criteria, such as undulating longitudinal profiles and "tunnel" shapes. These results are consistent with the hypothesis that overpressurized subglacial water circulation controls the formation of tunnel valleys.Tunnel valleys are elongated and overdeepened hollows, up to hundreds of kilometers long, several kilometers wide and hundreds of meters deep, and their formation is generally attributed to subglacial meltwater erosion [Ó Cofaigh, 1996;Huuse and Lykke-Andersen, 2000]. They are generally exposed at the emplacement of former ice sheet margins

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“…Rattas and Piotrowski (2003) demonstrated how the hydrogeological properties of the bed can modulate ice streaming and formation of specific subglacial landforms. Piotrowski and Kraus (1997) and Marczinek and Piotrowski (2006) suggested that in northwestern Germany pore-water pressure in the bed was probably close to the glacier flotation level, which indicated insufficient capacity of the substratum to drain all the incoming meltwater. Under such conditions an efficient channelized drainage system would develop, giving rise to deep linear erosion and formation of tunnel valleys (Huuse and Lykke-Andersen, 2000;Jørgensen and Sandersen, 2006;Kristensen et al, 2007) to prevent widespread basal decoupling and ice sheet collapse.…”

Section: Introductionmentioning

confidence: 99%

Meltwater discharge through the subglacial bed and its land‐forming consequences from numerical experiments in the Polish lowland during the last glaciation

Piotrowski

Hermanowski

Piechota

2009

Earth Surf Processes Landf

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Numerical experiments suggest that the last glaciation severely affected the upper lithosphere groundwater system in NW Poland: primarily its flow pattern, velocities and fluxes. We have simulated subglacial groundwater flow in two and three spatial dimensions using finite difference codes for steady-state and transient conditions. The results show how profoundly the ice sheet modifies groundwater pressure heads beneath and some distance beyond the ice margin. All model runs show water discharge at the ice forefield driven by ice-sheet-thickness-modulated, down-ice-decreasing hydraulic heads. In relation to nonglacial times, the transient 3D model shows significant changes in the groundwater flow directions in a regionally extensive aquifer ca. 90 m below the ice-bed interface and up to 40 km in front of the glacier. Comparison with empirical data suggests that, depending on the model run, only between 5 and 24% of the meltwater formed at the ice sole drained through the bed as groundwater. This is consistent with field observations documenting abundant occurrence of tunnel valleys, indicating that the remaining portion of basal meltwater was evacuated through a channelized subglacial drainage system. Groundwater flow simulation suggests that in areas of very low hydraulic conductivity and adverse subglacial slopes water ponding at the ice sole was likely. In these areas the relief shows distinct palaeo-ice lobes, indicating fast ice flow, possibly triggered by the undrained water at the ice-bed interface. Owing to the abundance of low-permeability strata in the bed, the simulated groundwater flow depth is less than ca. 200 m.

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Groundwater Flow Under the Margin of the Last Scandinavian Ice Sheet Around the EckernföRde Bay, Northwest Germany

Cited by 6 publications

References 0 publications

Modelled subglacial floods and tunnel valleys control the life cycle of transitory ice streams

Modelled subglacial floods and tunnel valleys control the life cycle of transitory ice streams

Experimental modeling of pressurized subglacial water flow: Implications for tunnel valley formation

Meltwater discharge through the subglacial bed and its land‐forming consequences from numerical experiments in the Polish lowland during the last glaciation

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