Geothermal Heat Flux in East Antarctica from HCA numerical modeling between 60-180°E Longitude

2020 ◽  
Author(s):  
Francesco Salvini ◽  
Paola Cianfarra ◽  
Giovanni Capponi ◽  
Laura Crispini ◽  
Laura Federico ◽  
...  
Keyword(s):  
Heat Flux ◽  
Spatial Distribution ◽  
Ice Sheet ◽  
East Antarctica ◽  
Heat Diffusion ◽  
Physical Parameters ◽  
Geothermal Heat ◽  
Ice Dynamics ◽  
Rock Interaction ◽  
Subglacial Lakes

<p>Estimation of subglacial Geothermal Heat Flux (GHF) is of paramount importance to better understand the dynamics  of cryosphere and ice flow of the East Antarctica Ice Sheet (EAIS). Unfortunately, the GHF of East Antarctica is still poorly known and constrained, and direct measurements are still challenging. The EIAS is underlain by major subglacial mountain ranges and basins resulting from distinct geodynamic domains. These include Northern Victoria Land-Ross Sea, the Transantarctic Mountains, the Wilkes Subglacial Basin, the Gamburtsev Subglacial Mountains, the East Antarctic System and a major transpressional fault zone in between (e.g. Cianfarra & Maggi, 2017), which hosts clusters of subglacial lakes. The distribution of sedimentary basins and tectonic structures may affect the GHF in that it exhibits strong regional variations as testified by the presence of subglacial lakes at bedrock topographic elevation/depth with a range exceeding 1500 m, from deep subglacial basins to the flanking highlands. In the framework of the G-IDEA (Geo Ice Dynamics of East Antarctica) project, heat flow from the basement is quantified in key areas of East Antarctica between 60°E and 180°E, by an innovative application of the HCA (Hybrid Cellular Automata) method: the description of stationary conditions of the temperature field is used to replicate the observed distribution of wet vs dry ice-rock contacts in an ice-flowing environment. Evaluation of the geothermal flux is performed in key areas based on the numeric modeling of the ice-rock interaction, which can replicate the spatial distribution of wet contacts and subglacial lakes and is related to local dynamics of the ice sheet and its interaction with the atmosphere. The model takes into account the spatial distribution of the Curie temperature depth as derived from literature. The heat flux is estimated by modeling the stationary state of the ice-rock system with the HCA numerical method, and by its discretization into a large number of cells. Each cell is characterized by physical parameters such as density, enthalpy, thermal capacity and conductivity. By their interaction it is possible to compute their temperature evolution and to replicate the heat diffusion by conduction and convection (the ice movement) in the interfaces ice-rock and ice-atmosphere. The final resolution of the model is about 100 m. The presence of possible anomalous heath flow in the bedrock are identified by a stochastic approach that allow the estimation of the error in the computed heath flow values.</p>

scholarly journals Forty-seven new subglacial lakes in the 0–110° E sector of East Antarctica

2007 ◽  
Vol 53 (181) ◽  
pp. 289-297 ◽  
Author(s):  
Sergey V. Popov ◽  
Valery N. Masolov
Keyword(s):  
Heat Flux ◽  
Scientific Work ◽  
East Antarctica ◽  
Lake Area ◽  
Geothermal Heat ◽  
Subglacial Lake ◽  
Deep Faults ◽  
Radio Echo Sounding ◽  
Subglacial Lakes ◽  
Echo Sounding

AbstractDuring the summer field seasons of 1987–91, studies of central East Antarctica by airborne radio-echo sounding commenced. This scientific work continued in the 1990s in the Vostok Subglacial Lake area and along the traverse route from Mirny, and led to the discovery of 16 new subglacial water cavities in the areas of Domes Fuji and Argus and the Prince Charles Mountains. Twenty-nine subglacial water cavities were revealed in the area near Vostok, along with a feature we believe to be a subglacial river. Two subglacial lakes were discovered along the Mirny–Vostok traverse route. These are located 50 km north of Komsomolskaya station and under Pionerskaya station. We find high geothermal heat flux in the vicinity of the largest of the subglacial lakes, and suggest this may be due to their location over deep faults where additional mantle heat is available.

scholarly journals Polythermal modelling of steady states of the Antarctic ice sheet in comparison with the real world

1996 ◽  
Vol 23 ◽  
pp. 382-387 ◽  
Author(s):  
I. Hansen ◽  
R. Greve
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Ice Sheet ◽  
Physical Parameters ◽  
Water Mixture ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
The Real ◽  
Thermomechanical Behaviour ◽  
The Antarctic

An approach to simulate the present Antarctic ice sheet with reaped to its thermomechanical behaviour and the resulting features is made with the three-dimensional polythermal ice-sheet model designed by Greve and Hutter. It treats zones of cold and temperate ice as different materials with their own properties and dynamics. This is important because an underlying layer of temperate ice can influence the ice sheet as a whole, e.g. the cold ice may slide upon the less viscous binary ice water mixture. Measurements indicate that the geothermal heat flux below the Antarctic ice sheet appears to be remarkably higher than the standard value of 42 m W m−2 that is usually applied for Precambrian shields in ice-sheet modelling. Since the extent of temperate ice at the base is highly dependent on this heat input from the lithosphere, an adequate choice is crucial for realistic simulations. We shall present a series of steady-state results with varied geothermal heat flux and demonstrate that the real ice-sheet topography can be reproduced fairly well with a value in the range 50–60 m W m−2. Thus, the physical parameters of ice (especially the enhancement factor in Glen’s flow law) as used by Greve (1995) for polythermal Greenland ice-sheet simulations can be adopted without any change. The remaining disagreements may he explained by the neglected influence of the ice shelves, the rather coarse horizontal resolution (100 km), the steady-state assumption and possible shortcomings in the parameterization of the surface mass balance.

scholarly journals Spatial variations in heat at the base of the Antarctic ice sheet from analysis of the thermal regime above subglacial lakes

1996 ◽  
Vol 42 (142) ◽  
pp. 501-509 ◽  
Author(s):  
Martin J. Siegert ◽  
Julian A. Dowdeswell
Keyword(s):  
Heat Flux ◽  
Melting Point ◽  
Thermal Model ◽  
Large Scale ◽  
Ice Sheet ◽  
Geothermal Heat ◽  
Vertical Advection ◽  
Basal Sliding ◽  
Pressure Melting ◽  
Subglacial Lakes

AbstractAntarctic subglacial lakes provide аn important boundary condition for thermal analysis of the ice sheet in that the basal ice temperature over lakes may be assumed to be at the pressure-melting point. We have used a one-dimensional vertical heat-transfer equation to determine theoretical temperature values for the ice-sheet base above 77 subglacial lakes identified from airborne radio-echo-sounding data covering 50% of Antarctica. Variations in our temperature results to below the pressure-melting temperature over lakes are due to either our estimate of the geothermal heat flux or a neglect of heat derived from (a) internal ice deformation and (b) basal sliding, in the thermal model. Our results indicate that, when the geothermal heat flux is set at 54 m W m−2, the ice-sheet base above 70% of the known Antarctic subglacial lakes is calculated to be at the pressure-melting value. These lakes are located mainly around Dome C, Ridge B and Vostok station. For the ice sheet above subglacial lakes located hundreds of kilometres from the ice divide, using the same thermal model, loss of heat due to vertical advection is calculated to be relatively high. In such regions, if the ice-sheet base is at the pressure-melting point, heat lost due to vertical advection must be supplemented by heat from other sources. For the three lakes beneath Terre Adélie and George V Land, for instance, the basal thermal gradient calculated to produce pressure melting at the ice-sheet base is equivalent to 1.5–2 times the value obtained when 54 m W m−2of geothermal heat is used as the sole basal thermal component. We suggest that, as distance from the ice divide increases, so too does the amount of heat due to internal ice deformation and basal sliding. Moreover, by considering the ice-sheet basal thermal characteristics above subglacial lakes which lie on the same ice flowline, we demonstrate empirically that the heat due to these horizontal ice-motion terms varies pseudo-exponentially with distance from the ice divide. The location along a flowline where a rapid increase in the basal heat gradient is calculated may correspond to the onset of large-scale basal sliding.

scholarly journals Inversion of Geothermal Heat Flux under the Ice Sheet of Princess Elizabeth Land, East Antarctica

2021 ◽  
Vol 13 (14) ◽  
pp. 2760
Author(s):  
Lin Li ◽  
Xueyuan Tang ◽  
Jingxue Guo ◽  
Xiangbin Cui ◽  
Enzhao Xiao ◽  
...  
Keyword(s):  
Heat Flux ◽  
Ice Sheet ◽  
Water System ◽  
East Antarctica ◽  
Dynamics Simulation ◽  
Geothermal Heat ◽  
Curie Depth ◽  
Ice Sheet Dynamics ◽  
Steady State Heat ◽  
The One

Antarctic geothermal heat flux is a basic input variable for ice sheet dynamics simulation. It greatly affects the temperature and mechanical properties at the bottom of the ice sheet, influencing sliding, melting, and internal deformation. Due to the fact that the Antarctica is covered by a thick ice sheet, direct measurements of heat flux are very limited. This study was carried out to estimate the regional heat flux in the Antarctic continent through geophysical inversion. Princess Elizabeth Land, East Antarctica is one of the areas in which we have a weak understanding of geothermal heat flux. Through the latest airborne geomagnetic data, we inverted the Curie depth, obtaining the heat flux of bedrock based on the one-dimensional steady-state heat conduction equation. The results indicated that the Curie depth of the Princess Elizabeth Land is shallower than previously estimated, and the heat flux is consequently higher. Thus, the contribution of subglacial heat flux to the melting at the bottom of the ice sheet is likely greater than previously expected in this region. It further provides research clues for the formation of the developed subglacial water system in Princess Elizabeth Land.

scholarly journals Polythermal modelling of steady states of the Antarctic ice sheet in comparison with the real world

1996 ◽  
Vol 23 ◽  
pp. 382-387 ◽  
Author(s):  
I. Hansen ◽  
R. Greve
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Ice Sheet ◽  
Physical Parameters ◽  
Water Mixture ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
The Real ◽  
Thermomechanical Behaviour ◽  
The Antarctic

An approach to simulate the present Antarctic ice sheet with reaped to its thermomechanical behaviour and the resulting features is made with the three-dimensional polythermal ice-sheet model designed by Greve and Hutter. It treats zones of cold and temperate ice as different materials with their own properties and dynamics. This is important because an underlying layer of temperate ice can influence the ice sheet as a whole, e.g. the cold ice may slide upon the less viscous binary ice water mixture.Measurements indicate that the geothermal heat flux below the Antarctic ice sheet appears to be remarkably higher than the standard value of 42 m W m−2 that is usually applied for Precambrian shields in ice-sheet modelling. Since the extent of temperate ice at the base is highly dependent on this heat input from the lithosphere, an adequate choice is crucial for realistic simulations. We shall present a series of steady-state results with varied geothermal heat flux and demonstrate that the real ice-sheet topography can be reproduced fairly well with a value in the range 50–60 m W m−2. Thus, the physical parameters of ice (especially the enhancement factor in Glen’s flow law) as used by Greve (1995) for polythermal Greenland ice-sheet simulations can be adopted without any change. The remaining disagreements may he explained by the neglected influence of the ice shelves, the rather coarse horizontal resolution (100 km), the steady-state assumption and possible shortcomings in the parameterization of the surface mass balance.

scholarly journals Exceptionally high heat flux needed to sustain the Northeast Greenland Ice Stream

2020 ◽  
Vol 14 (3) ◽  
pp. 841-854 ◽  
Author(s):  
Silje Smith-Johnsen ◽  
Basile de Fleurian ◽  
Nicole Schlegel ◽  
Helene Seroussi ◽  
Kerim Nisancioglu
Keyword(s):  
Heat Flux ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
High Heat ◽  
High Heat Flux ◽  
Good Representation ◽  
Geothermal Heat ◽  
Ice Dynamics ◽  
Ice Stream

Abstract. The Northeast Greenland Ice Stream (NEGIS) currently drains more than 10 % of the Greenland Ice Sheet area and has recently undergone significant dynamic changes. It is therefore critical to accurately represent this feature when assessing the future contribution of Greenland to sea level rise. At present, NEGIS is reproduced in ice sheet models by inferring basal conditions using observed surface velocities. This approach helps estimate conditions at the base of the ice sheet but cannot be used to estimate the evolution of basal drag in time, so it is not a good representation of the evolution of the ice sheet in future climate warming scenarios. NEGIS is suggested to be initiated by a geothermal heat flux anomaly close to the ice divide, left behind by the movement of Greenland over the Icelandic plume. However, the heat flux underneath the ice sheet is largely unknown, except for a few direct measurements from deep ice core drill sites. Using the Ice Sheet System Model (ISSM), with ice dynamics coupled to a subglacial hydrology model, we investigate the possibility of initiating NEGIS by inserting heat flux anomalies with various locations and intensities. In our model experiment, a minimum heat flux value of 970 mW m−2 located close to the East Greenland Ice-core Project (EGRIP) is required locally to reproduce the observed NEGIS velocities, giving basal melt rates consistent with previous estimates. The value cannot be attributed to geothermal heat flux alone and we suggest hydrothermal circulation as a potential explanation for the high local heat flux. By including high heat flux and the effect of water on sliding, we successfully reproduce the main characteristics of NEGIS in an ice sheet model without using data assimilation.

scholarly journals Spatial variations in heat at the base of the Antarctic ice sheet from analysis of the thermal regime above subglacial lakes

1996 ◽  
Vol 42 (142) ◽  
pp. 501-509 ◽  
Author(s):  
Martin J. Siegert ◽  
Julian A. Dowdeswell
Keyword(s):  
Heat Flux ◽  
Melting Point ◽  
Thermal Model ◽  
Large Scale ◽  
Ice Sheet ◽  
Geothermal Heat ◽  
Vertical Advection ◽  
Basal Sliding ◽  
Pressure Melting ◽  
Subglacial Lakes

AbstractAntarctic subglacial lakes provide аn important boundary condition for thermal analysis of the ice sheet in that the basal ice temperature over lakes may be assumed to be at the pressure-melting point. We have used a one-dimensional vertical heat-transfer equation to determine theoretical temperature values for the ice-sheet base above 77 subglacial lakes identified from airborne radio-echo-sounding data covering 50% of Antarctica. Variations in our temperature results to below the pressure-melting temperature over lakes are due to either our estimate of the geothermal heat flux or a neglect of heat derived from (a) internal ice deformation and (b) basal sliding, in the thermal model. Our results indicate that, when the geothermal heat flux is set at 54 m W m−2, the ice-sheet base above 70% of the known Antarctic subglacial lakes is calculated to be at the pressure-melting value. These lakes are located mainly around Dome C, Ridge B and Vostok station. For the ice sheet above subglacial lakes located hundreds of kilometres from the ice divide, using the same thermal model, loss of heat due to vertical advection is calculated to be relatively high. In such regions, if the ice-sheet base is at the pressure-melting point, heat lost due to vertical advection must be supplemented by heat from other sources. For the three lakes beneath Terre Adélie and George V Land, for instance, the basal thermal gradient calculated to produce pressure melting at the ice-sheet base is equivalent to 1.5–2 times the value obtained when 54 m W m−2 of geothermal heat is used as the sole basal thermal component. We suggest that, as distance from the ice divide increases, so too does the amount of heat due to internal ice deformation and basal sliding. Moreover, by considering the ice-sheet basal thermal characteristics above subglacial lakes which lie on the same ice flowline, we demonstrate empirically that the heat due to these horizontal ice-motion terms varies pseudo-exponentially with distance from the ice divide. The location along a flowline where a rapid increase in the basal heat gradient is calculated may correspond to the onset of large-scale basal sliding.

scholarly journals Exceptionally High Geothermal Heat Flux Needed to Sustain the Northeast Greenland Ice Stream

2019 ◽  
Author(s):  
Silje Smith-Johnsen ◽  
Basile de Fleurian ◽  
Nicole Schlegel ◽  
Helene Seroussi ◽  
Kerim Nisanciolgu
Keyword(s):  
Heat Flux ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Good Representation ◽  
Geothermal Heat ◽  
Ice Dynamics ◽  
Left Behind ◽  
Ice Stream ◽  
Using Data

Abstract. The Northeast Greenland Ice Stream (NEGIS) currently drains more than 10 % of the Greenland Ice Sheet area, and has recently undergone significant dynamic changes. It is therefore critical to accurately represent this feature when assessing the future contribution of Greenland to sea level rise. At present, NEGIS is reproduced in ice sheet models by inferring basal conditions using observed surface velocities. This approach helps estimate conditions at the base of the ice sheet, but cannot be used to estimate the evolution of basal drag in time, so it is not a good representation of the evolution of the ice sheet in future climate warming scenarios. NEGIS is suggested to be initiated by a geothermal heat flux anomaly close to the ice divide, left behind by the movement of Greenland over the Icelandic plume. However, the heat flux underneath the ice sheet is largely unknown, except for a few direct measurements from deep ice core drill sites. Using the Ice Sheet System Model (ISSM), with ice dynamics coupled to a subglacial hydrology model, we investigate the possibility of initiating NEGIS by inserting hotspots with various locations and intensities. We find that a minimum geothermal heat flux value of 970 mW/m2 located close to EastGRIP is required locally to reproduce the observed NEGIS velocities, consistent with previous estimates. By including high geothermal heat flux and the effect of water on sliding, we successfully reproduce the main characteristics of NEGIS in an ice sheet model without using data assimilation.

scholarly journals The impact of parametric uncertainty and topographic error in ice-sheet modelling

2008 ◽  
Vol 54 (188) ◽  
pp. 899-919 ◽  
Author(s):  
Felix Hebeler ◽  
Ross S. Purves ◽  
Stewart S.R. Jamieson
Keyword(s):  
Heat Flux ◽  
Input Data ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Parametric Uncertainty ◽  
Lapse Rate ◽  
Model Parameters ◽  
Geothermal Heat ◽  
Ice Dynamics ◽  
The Impact

AbstractIce-sheet models (ISMs) developed to simulate the behaviour of continental-scale ice sheets under past, present or future climate scenarios are subject to a number of uncertainties from various sources. These sources include the conceptualization of the ISM and the degree of abstraction and parameterizations of processes such as ice dynamics and mass balance. The assumption of spatially or temporally constant parameters (such as degree-day factor, atmospheric lapse rate or geothermal heat flux) is one example. Additionally, uncertainties in ISM input data such as topography or precipitation propagate to the model results. In order to assess and compare the impact of uncertainties from model parameters and climate on the GLIMMER ice-sheet model, a parametric uncertainty analysis (PUA) was conducted. Parameter variation was deduced from a suite of sensitivity tests, and accuracy information was deduced from input data and the literature. Recorded variation of modelled ice extent across the PUA runs was 65% for equilibrium ice sheets. Additionally, the susceptibility of ISM results to modelled uncertainty in input topography was assessed. Resulting variations in modelled ice extent in the range of 0.8–6.6% are comparable to that of ISM parameters such as flow enhancement, basal traction and geothermal heat flux.

scholarly journals Refined broad-scale sub-glacial morphology of Aurora Subglacial Basin, East Antarctica derived by an ice-dynamics-based interpolation scheme

2011 ◽  
Vol 5 (3) ◽  
pp. 551-560 ◽  
Author(s):  
J. L. Roberts ◽  
R. C. Warner ◽  
D. Young ◽  
A. Wright ◽  
T. D. van Ommen ◽  
...  
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
East Antarctica ◽  
Geometric Constraints ◽  
Ice Thickness ◽  
Interpolation Scheme ◽  
Ice Dynamics ◽  
High Resolution Data ◽  
Physically Based ◽  
Glacial Morphology

Abstract. Ice thickness data over much of East Antarctica are sparse and irregularly distributed. This poses difficulties for reconstructing the homogeneous coverage needed to properly assess underlying sub-glacial morphology and fundamental geometric constraints on sea level rise. Here we introduce a new physically-based ice thickness interpolation scheme and apply this to existing ice thickness data in the Aurora Subglacial Basin region. The skill and robustness of the new reconstruction is demonstrated by comparison with new data from the ICECAP project. The interpolated morphology shows an extensive marine-based ice sheet, with considerably more area below sea-level than shown by prior studies. It also shows deep features connecting the coastal grounding zone with the deepest regions in the interior. This has implications for ice sheet response to a warming ocean and underscores the importance of obtaining additional high resolution data in these marginal zones for modelling ice sheet evolution.

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