2019 CSDMS meeting-073: Difference between revisions

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|CSDMS meeting abstract title=Modeled Postglacial Landscape Evolution at the Southern Margin of the Laurentide Ice Sheet: Hydrological Connection of Uplands Controls the Pace and Style of Fluvial Network Expansion
|CSDMS meeting abstract title=The impact of geothermal flux on patterns and rates of glacial erosion
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{{CSDMS meeting abstract template 2019
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|CSDMS meeting abstract=Landscapes of the US Central Lowland were repeatedly affected by the Laurentide Ice Sheet. Glacial processes diminished relief and disrupted drainage networks. Deep valleys carved by glacial meltwater were disconnected from the surrounding uplands. The upland area lacking surface water connection to the drainage network is referred to as non-contributing area (NCA). Decreasing fractions of NCA on older surfaces suggests that NCA becomes drained over time. We propose that the integration could occur via: 1) capture of NCA as channels propagate into the upland or, 2) subsurface or intermittent surface connection of NCA to external drainage networks providing increased discharge to promote channel incision. We refer the two cases as “disconnected” and “connected” since the crucial difference between them is the hydrological connection of the upland to external drainage. We investigate the differences in evolution and morphology of channel networks in low relief landscapes under disconnected and connected regimes using the LandLab landscape evolution modeling platform. We observe substantially faster rates of erosion and integration of the channel network in the connected case. The connected case also creates longer, more sinuous channels than the disconnected case. Sensitivity tests indicate that hillslope diffusivity has little influence on the evolution and morphology. The fluvial erosion coefficient has significant impact on the rate of evolution, and it influences the morphology to a lesser extent. Our results and a qualitative comparison with landscapes of the glaciated US Central Lowland suggest that connection of NCAs is a potential control on the evolution and morphology of post-glacial landscapes.
|CSDMS meeting abstract=Glacial erosion has shaped many high mountain belts during the cold periods of the Late Cenozoic. Theoretical models of glacial erosion generally link the pace of erosion to some subglacial properties including basal sliding, basal thermal regime, and effective water pressure. The energy balance of glaciers is a strong control on ice dynamics and therefore, has a potential impact on glacial erosion. Specifically, the geothermal heat from the bedrock can potentially control the patterns and rates of glacial erosion by changing the basal temperature and the supply of meltwater to the subglacial water system. Here, we investigate the impact of geothermal heat flow on glacial erosion using a coupled model of glacial erosion and ice dynamics. The rate of glacial erosion is modeled as a linear function of the basal sliding speed. The ice flow is modeled using the Parallel Ice Sheet Model (PISM). PISM solves the conservation of energy using an enthalpy-based scheme. The basal sliding is linked to subglacial hydrology through a pseudo-plastic basal resistance model. We model glacial erosion over a synthetic glacial landscape using various values of geothermal heat flux. Preliminary results demonstrate that higher geothermal heat flux can increase the total erosion significantly by accelerating the rate of basal sliding and expanding the area of sliding into higher elevations.
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Revision as of 16:43, 1 April 2019





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The impact of geothermal flux on patterns and rates of glacial erosion

Jingtao Lai, University of Illinois at Urbana-Champaign Urbana Illinois, United States. jlai11@illinois.edu
Alison Anders, University of Illinois at Urbana-Champaign Illinois, United States. amanders@illinois.edu


Glacial erosion has shaped many high mountain belts during the cold periods of the Late Cenozoic. Theoretical models of glacial erosion generally link the pace of erosion to some subglacial properties including basal sliding, basal thermal regime, and effective water pressure. The energy balance of glaciers is a strong control on ice dynamics and therefore, has a potential impact on glacial erosion. Specifically, the geothermal heat from the bedrock can potentially control the patterns and rates of glacial erosion by changing the basal temperature and the supply of meltwater to the subglacial water system. Here, we investigate the impact of geothermal heat flow on glacial erosion using a coupled model of glacial erosion and ice dynamics. The rate of glacial erosion is modeled as a linear function of the basal sliding speed. The ice flow is modeled using the Parallel Ice Sheet Model (PISM). PISM solves the conservation of energy using an enthalpy-based scheme. The basal sliding is linked to subglacial hydrology through a pseudo-plastic basal resistance model. We model glacial erosion over a synthetic glacial landscape using various values of geothermal heat flux. Preliminary results demonstrate that higher geothermal heat flux can increase the total erosion significantly by accelerating the rate of basal sliding and expanding the area of sliding into higher elevations.


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