scholarly journals Topographic controls on channelized meltwater in the subglacial environment

2021 ◽  
Author(s):  
L. M. Simkins ◽  
S. L. Greenwood ◽  
S. Munevar Garcia ◽  
E. A. Eareckson ◽  
J. B. Anderson ◽  
...  
Keyword(s):  
Subglacial Environment ◽  
Topographic Controls

scholarly journals Modeling Antarctic subglacial lake filling and drainage cycles

2016 ◽  
Vol 10 (4) ◽  
pp. 1381-1393 ◽  
Author(s):  
Christine F. Dow ◽  
Mauro A. Werder ◽  
Sophie Nowicki ◽  
Ryan T. Walker
Keyword(s):  
Internal Controls ◽  
Water Volume ◽  
Lake Basin ◽  
Subglacial Lake ◽  
Subglacial Environment ◽  
Ice Surface ◽  
Ice Stream ◽  
Slow Moving ◽  
Lake Drainage ◽  
Subglacial Lakes

Abstract. The growth and drainage of active subglacial lakes in Antarctica has previously been inferred from analysis of ice surface altimetry data. We use a subglacial hydrology model applied to a synthetic Antarctic ice stream to examine internal controls on the filling and drainage of subglacial lakes. Our model outputs suggest that the highly constricted subglacial environment of our idealized ice stream, combined with relatively high rates of water flow funneled from a large catchment, can combine to create a system exhibiting slow-moving pressure waves. Over a period of years, the accumulation of water in the ice stream onset region results in a buildup of pressure creating temporary channels, which then evacuate the excess water. This increased flux of water beneath the ice stream drives lake growth. As the water body builds up, it steepens the hydraulic gradient out of the overdeepened lake basin and allows greater flux. Eventually this flux is large enough to melt channels that cause the lake to drain. Lake drainage also depends on the internal hydrological development in the wider system and therefore does not directly correspond to a particular water volume or depth. This creates a highly temporally and spatially variable system, which is of interest for assessing the importance of subglacial lakes in ice stream hydrology and dynamics.

scholarly journals Efficacy of bedrock erosion by subglacial water flow

2015 ◽  
Vol 3 (3) ◽  
pp. 849-908 ◽  
Author(s):  
F. Beaud ◽  
G. E. Flowers ◽  
J. G. Venditti
Keyword(s):  
Water Flow ◽  
Water Pressure ◽  
Water Discharge ◽  
Sediment Supply ◽  
Fluvial Systems ◽  
Glacial Meltwater ◽  
Erosion Rates ◽  
Subglacial Environment ◽  
Basin Scale ◽  
Bedrock Erosion

Abstract. Bedrock erosion by sediment-bearing subglacial water remains little-studied, however the process is thought to contribute to bedrock erosion rates in glaciated landscapes and is implicated in the excavation of tunnel valleys and the incision of inner gorges. We adapt physics-based models of fluvial abrasion to the subglacial environment, assembling the first model designed to quantify bedrock erosion caused by transient subglacial water flow. The subglacial drainage model consists of a one-dimensional network of cavities dynamically coupled to one or several Röthlisberger channels (R-channels). The bedrock erosion model is based on the tools and cover effect, whereby particles entrained by the flow impact exposed bedrock. We explore the dependency of glacial meltwater erosion on the structure and magnitude of water input to the system, the ice geometry and the sediment supply. We find that erosion is not a function of water discharge alone, but also depends on channel size, water pressure and on sediment supply, as in fluvial systems. Modelled glacial meltwater erosion rates are one to two orders of magnitude lower than the expected rates of total glacial erosion required to produce the sediment supply rates we impose, suggesting that glacial meltwater erosion is negligible at the basin scale. Nevertheless, due to the extreme localization of glacial meltwater erosion (at the base of R-channels), this process can carve bedrock (Nye) channels. In fact, our simulations suggest that the incision of bedrock channels several centimetres deep and a few meters wide can occur in a single year. Modelled incision rates indicate that subglacial water flow can gradually carve a tunnel valley and enhance the relief or even initiate the carving of an inner gorge.

Topographic controls on gravity currents in porous media

2013 ◽  
Vol 734 ◽  
pp. 317-337 ◽  
Author(s):  
Samuel S. Pegler ◽  
Herbert E. Huppert ◽  
Jerome A. Neufeld
Keyword(s):  
Porous Media ◽  
Axisymmetric Flow ◽  
Early Time ◽  
Gravity Currents ◽  
Late Time ◽  
Horizontal Distance ◽  
Topographic Controls ◽  
Time Regime ◽  
Flow Transitions ◽  
Theoretical Results

AbstractWe present a theoretical and experimental study of the propagation of gravity currents in porous media with variations in the topography over which they flow, motivated in part by the sequestration of carbon dioxide in saline aquifers. We consider cases where the height of the topography slopes upwards in the direction of the flow and is proportional to the $n\text{th} $ power of the horizontal distance from a line or point source of a constant volumetric flux. In two-dimensional cases with $n\gt 1/ 2$, the current evolves from a self-similar form at early times, when the effects of variations in topography are negligible, towards a late-time regime that has an approximately horizontal upper surface and whose evolution is dictated entirely by the geometry of the topography. For $n\lt 1/ 2$, the transition between these flow regimes is reversed. We compare our theoretical results in the case $n= 1$ with data from a series of laboratory experiments in which viscous glycerine is injected into an inclined Hele-Shaw cell, obtaining good agreement between the theoretical results and the experimental data. In the case of axisymmetric topography, all topographic exponents $n\gt 0$ result in a transition from an early-time similarity solution towards a topographically controlled regime that has an approximately horizontal free surface. We also analyse the evolution over topography that can vary with different curvatures and topographic exponents between the two horizontal dimensions, finding that the flow transitions towards a horizontally topped regime at a rate which depends strongly on the ratio of the curvatures along the principle axes. Finally, we apply our mathematical solutions to the geophysical setting at the Sleipner field, concluding that topographic influence is unlikely to explain the observed non-axisymmetric flow.

scholarly journals Quantifying supraglacial meltwater pathways in the Paakitsoq region, West Greenland

2017 ◽  
Vol 63 (239) ◽  
pp. 464-476 ◽  
Author(s):  
CONRAD KOZIOL ◽  
NEIL ARNOLD ◽  
ALLEN POPE ◽  
WILLIAM COLGAN
Keyword(s):  
Spatial Patterns ◽  
Surface Runoff ◽  
Significant Proportion ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Average Intensity ◽  
West Greenland ◽  
Surface Drainage ◽  
Subglacial Environment ◽  
Hydrology Model

ABSTRACTIncreased summer ice velocities on the Greenland ice sheet are driven by meltwater input to the subglacial environment. However, spatial patterns of surface input and partitioning of meltwater between different pathways to the base remain poorly understood. To further our understanding of surface drainage, we apply a supraglacial hydrology model to the Paakitsoq region, West Greenland for three contrasting melt seasons. During an average melt season, crevasses drain ~47% of surface runoff, lake hydrofracture drains ~3% during the hydrofracturing events themselves, while the subsequent surface-to-bed connections drain ~21% and moulins outside of lake basins drain ~15%. Lake hydrofracture forms the primary drainage pathway at higher elevations (above ~850 m) while crevasses drain a significant proportion of meltwater at lower elevations. During the two higher intensity melt seasons, model results show an increase (~5 and ~6% of total surface runoff) in the proportion of runoff drained above ~1300 m relative to the melt season of average intensity. The potential for interannual changes in meltwater partitioning could have implications for how the dynamics of the ice sheet respond to ongoing changes in meltwater production.

Topographic controls on glacier sediment–landform associations around the temperate North Patagonian Icefield

2009 ◽  
Vol 28 (25-26) ◽  
pp. 2817-2832 ◽  
Author(s):  
Neil F. Glasser ◽  
Stephan Harrison ◽  
Krister N. Jansson
Keyword(s):  
Topographic Controls

scholarly journals Topographic controls on the surging behaviour of Sabche Glacier, Nepal (1967 to 2017)

2018 ◽  
Vol 210 ◽  
pp. 434-443 ◽  
Author(s):  
Arminel M. Lovell ◽  
J. Rachel Carr ◽  
Chris R. Stokes
Keyword(s):  
Topographic Controls

scholarly journals Geomorphic transience moderates topographic controls on tropical canopy foliar traits

2020 ◽  
Vol 23 (8) ◽  
pp. 1276-1286 ◽  
Author(s):  
K. Dana Chadwick ◽  
Gregory P. Asner
Keyword(s):  
Topographic Controls ◽  
Foliar Traits

Topographic controls on the variability of soil respiration in a humid subtropical forest

2019 ◽  
Vol 145 (1-2) ◽  
pp. 177-192 ◽  
Author(s):  
Qiuxiang Tian ◽  
Dongya Wang ◽  
Yanan Tang ◽  
Yi Li ◽  
Min Wang ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Subtropical Forest ◽  
Topographic Controls

scholarly journals Topographic Controls On the Development of Contemporaneous but Contrasting Basin-Floor Depositional Architectures

2018 ◽  
Vol 88 (10) ◽  
pp. 1166-1189 ◽  
Author(s):  
Daniel Bell ◽  
Christopher J. Stevenson ◽  
Ian A. Kane ◽  
David M. Hodgson ◽  
Miquel Poyatos-Moré
Keyword(s):  
Topographic Controls ◽  
Basin Floor
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