scholarly journals Geothermal heat flux from measured temperature profiles in deep ice boreholes in Antarctica

2020 ◽  
Vol 14 (11) ◽  
pp. 4021-4037
Author(s):  
Pavel Talalay ◽  
Yazhou Li ◽  
Laurent Augustin ◽  
Gary D. Clow ◽  
Jialin Hong ◽  
...  
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Heat Flow ◽  
Ice Sheet ◽  
Temperature Profiles ◽  
The West ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
West Antarctic ◽  
Steady State Model

Abstract. The temperature at the Antarctic Ice Sheet bed and the temperature gradient in subglacial rocks have been directly measured only a few times, although extensive thermodynamic modeling has been used to estimate the geothermal heat flux (GHF) under the ice sheet. During the last 5 decades, deep ice-core drilling projects at six sites – Byrd, WAIS Divide, Dome C, Kohnen, Dome F, and Vostok – have succeeded in reaching or nearly reaching the bed at inland locations in Antarctica. When temperature profiles in these boreholes and steady-state heat flow modeling are combined with estimates of vertical velocity, the heat flow at the ice-sheet base is translated to a geothermal heat flux of 57.9 ± 6.4 mW m−2 at Dome C, 78.9 ± 5.0 mW m−2 at Dome F, and 86.9 ± 16.6 mW m−2 at Kohnen, all higher than the predicted values at these sites. This warm base under the East Antarctic Ice Sheet (EAIS) could be caused by radiogenic heat effects or hydrothermal circulation not accounted for by the models. The GHF at the base of the ice sheet at Vostok has a negative value of −3.6 ± 5.3 mW m−2, indicating that water from Lake Vostok is freezing onto the ice-sheet base. Correlation analyses between modeled and measured depth–age scales at the EAIS sites indicate that all of them can be adequately approximated by a steady-state model. Horizontal velocities and their variation over ice-age cycles are much greater for the West Antarctic Ice Sheet than for the interior EAIS sites; a steady-state model cannot precisely describe the temperature distribution here. Even if the correlation factors for the best fitting age–depth curve are only moderate for the West Antarctic sites, the GHF values estimated here of 88.4 ± 7.6 mW m−2 at Byrd and 113.3 ± 16.9 mW m−2 at WAIS Divide can be used as references before more precise estimates are made on the subject.

scholarly journals High geothermal heat flux measured below the West Antarctic Ice Sheet

2015 ◽  
Vol 1 (6) ◽  
pp. e1500093 ◽  
Author(s):  
Andrew T. Fisher ◽  
Kenneth D. Mankoff ◽  
Slawek M. Tulaczyk ◽  
Scott W. Tyler ◽  
Neil Foley ◽  
...  
Keyword(s):  
Heat Flux ◽  
Ice Sheet ◽  
The West ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Subglacial Lake ◽  
West Antarctic ◽  
Basal Melting ◽  
Subglacial Lake Whillans

The geothermal heat flux is a critical thermal boundary condition that influences the melting, flow, and mass balance of ice sheets, but measurements of this parameter are difficult to make in ice-covered regions. We report the first direct measurement of geothermal heat flux into the base of the West Antarctic Ice Sheet (WAIS), below Subglacial Lake Whillans, determined from the thermal gradient and the thermal conductivity of sediment under the lake. The heat flux at this site is 285 ± 80 mW/m2, significantly higher than the continental and regional averages estimated for this site using regional geophysical and glaciological models. Independent temperature measurements in the ice indicate an upward heat flux through the WAIS of 105 ± 13 mW/m2. The difference between these heat flux values could contribute to basal melting and/or be advected from Subglacial Lake Whillans by flowing water. The high geothermal heat flux may help to explain why ice streams and subglacial lakes are so abundant and dynamic in this region.

scholarly journals Geothermal flux beneath the Antarctic Ice Sheet derived from measured temperature profiles in deep boreholes

2020 ◽  
Author(s):  
Pavel Talalay ◽  
Yazhou Li ◽  
Laurent Augustin ◽  
Gary Clow ◽  
Jialin Hong ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Flow ◽  
Ice Core ◽  
Ice Sheet ◽  
High Heat ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
The Antarctic

Abstract. The temperature at the Antarctic ice sheet bed and the temperature gradient in subglacial rocks have been directly measured only a few times, although extensive thermodynamic modelling has been used to estimate geothermal heat flux under ice sheet. During the last five decades, deep ice-core drilling projects at six sites – Byrd, WAIS Divide, Dome C, Kohnen, Dome F, and Vostok – have succeeded in reaching to, or nearly to, the bed in inland locations in Antarctica. When temperature profiles in these boreholes and heat flow model are combined with estimations of vertical velocity, the heat flow at ice sheet base is translated to a geothermal heat flux of 117.8 ± 3.3 mW m−2 at Byrd, 67.3 ± 8.6 mW m−2 at Dome C, 79.0 ± 5.0 mW m−2 at Dome F, and −3.3 ± 5.6 mW m−2 at Vostok, close to predicted values. However, estimations at Kohnen and WAIS Divide gave flux of 161.5 ± 10.2 mW m−2 and 251.3 ± 24.1 mW m−2, respectively, far higher than that predicted by existing heat flow models. The question arises as to whether this high heat flow represents regional values, or if the Kohnen and WAIS Divide boreholes were drilled over local hot spots.

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 High geothermal heat flow beneath Thwaites Glacier in West Antarctica inferred from aeromagnetic data

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Ricarda Dziadek ◽  
Fausto Ferraccioli ◽  
Karsten Gohl
Keyword(s):  
Heat Flow ◽  
Ice Sheet ◽  
West Antarctica ◽  
The West ◽  
Geothermal Heat ◽  
Amundsen Sea ◽  
Continental Scale ◽  
West Antarctic ◽  
Curie Depth ◽  
Depth Analysis

AbstractGeothermal heat flow in the polar regions plays a crucial role in understanding ice-sheet dynamics and predictions of sea level rise. Continental-scale indirect estimates often have a low spatial resolution and yield largest discrepancies in West Antarctica. Here we analyse geophysical data to estimate geothermal heat flow in the Amundsen Sea Sector of West Antarctica. With Curie depth analysis based on a new magnetic anomaly grid compilation, we reveal variations in lithospheric thermal gradients. We show that the rapidly retreating Thwaites and Pope glaciers in particular are underlain by areas of largely elevated geothermal heat flow, which relates to the tectonic and magmatic history of the West Antarctic Rift System in this region. Our results imply that the behavior of this vulnerable sector of the West Antarctic Ice Sheet is strongly coupled to the dynamics of the underlying lithosphere.

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 Inferring geothermal heat flux from an ice-borehole temperature profile at Law Dome, East Antarctica

2020 ◽  
Vol 66 (257) ◽  
pp. 509-519 ◽  
Author(s):  
Laura Mony ◽  
Jason L. Roberts ◽  
Jacqueline A. Halpin
Keyword(s):  
Heat Flux ◽  
Temperature Profile ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Ice Thickness ◽  
Temperature Profiles ◽  
Geothermal Heat ◽  
Absolute Deviation ◽  
West Antarctic ◽  
Borehole Temperature

AbstractGeothermal heat flux (GHF) is an important control on the dynamics of Antarctica's ice sheet because it controls basal melt and internal deformation. However, it is hard to estimate because of a lack of in-situ measurements. Estimating GHF from ice-borehole temperature profiles is possible by combining a heat-transfer equation and the physical properties of the ice sheet in a numerical model. In this study, we truncate ice-borehole temperature profiles to determine the minimum ratio of temperature profile depth to ice-sheet thickness required to produce acceptable GHF estimations. For Law Dome, a temperature profile that is within 60% of the local ice thickness is sufficient for an estimation that is within approximately one median absolute deviation of the whole-profile GHF estimation. This result is compared with the temperature profiles at Dome Fuji and the West Antarctic Ice Sheet divide which require a temperature profile that is 80% and more than 91% of the ice thickness, respectively, for comparable accuracy. In deriving GHF median estimations from truncated temperature profiles, it is possible to discriminate between available GHF models. This is valuable for assessing and constraining future GHF models.

Grounding-line retreat of the West Antarctic Ice Sheet from inner Pine Island Bay

Geology ◽  
2012 ◽  
Vol 41 (1) ◽  
pp. 35-38 ◽  
Author(s):  
C.-D. Hillenbrand ◽  
G. Kuhn ◽  
J. A. Smith ◽  
K. Gohl ◽  
A. G. C. Graham ◽  
...  
Keyword(s):  
Ice Sheet ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Grounding Line

scholarly journals A Potential Disintegration of the West Antarctic Ice Sheet: Implications for Economic Analyses of Climate Policy

2016 ◽  
Vol 106 (5) ◽  
pp. 607-611 ◽  
Author(s):  
Delavane Diaz ◽  
Klaus Keller
Keyword(s):  
Climate Policy ◽  
Expert Knowledge ◽  
Ice Sheet ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Threshold Response ◽  
West Antarctic ◽  
Climate Forcings ◽  
Economic Analyses

The Earth system may react in a nonlinear threshold response to climate forcings. Incorporating threshold responses into integrated assessment models (IAMs) used for climate policy analysis poses nontrivial challenges, for example due to methodological limitations and pervasive deep uncertainties. Here we explore a specific threshold response, a potential disintegration of the West Antarctic Ice Sheet (WAIS). We review the current scientific understanding of WAIS, identify methodological and conceptual issues, and demonstrate avenues to address some of them through a stochastic hazard IAM framework combining emulation, expert knowledge, and learning. We conclude with a discussion of challenges and research needs.

scholarly journals Simultaneous solution for mass trends on the West Antarctic Ice Sheet

2014 ◽  
Vol 8 (3) ◽  
pp. 2995-3035 ◽  
Author(s):  
N. Schön ◽  
A. Zammit-Mangion ◽  
J. L. Bamber ◽  
J. Rougier ◽  
T. Flament ◽  
...  
Keyword(s):  
Mass Loss ◽  
Antarctic Peninsula ◽  
Ice Sheet ◽  
The West ◽  
Spatial Error ◽  
Antarctic Ice Sheet ◽  
Forward Models ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
The Antarctic

Abstract. The Antarctic Ice Sheet is the largest potential source of future sea-level rise. Mass loss has been increasing over the last two decades in the West Antarctic Ice Sheet (WAIS), but with significant discrepancies between estimates, especially for the Antarctic Peninsula. Most of these estimates utilise geophysical models to explicitly correct the observations for (unobserved) processes. Systematic errors in these models introduce biases in the results which are difficult to quantify. In this study, we provide a statistically rigorous, error-bounded trend estimate of ice mass loss over the WAIS from 2003–2009 which is almost entirely data-driven. Using altimetry, gravimetry, and GPS data in a hierarchical Bayesian framework, we derive spatial fields for ice mass change, surface mass balance, and glacial isostatic adjustment (GIA) without relying explicitly on forward models. The approach we use separates mass and height change contributions from different processes, reproducing spatial features found in, for example, regional climate and GIA forward models, and provides an independent estimate, which can be used to validate and test the models. In addition, full spatial error estimates are derived for each field. The mass loss estimates we obtain are smaller than some recent results, with a time-averaged mean rate of −76 ± 15 GT yr−1 for the WAIS and Antarctic Peninsula (AP), including the major Antarctic Islands. The GIA estimate compares very well with results obtained from recent forward models (IJ05-R2) and inversion methods (AGE-1). Due to its computational efficiency, the method is sufficiently scalable to include the whole of Antarctica, can be adapted for other ice sheets and can easily be adapted to assimilate data from other sources such as ice cores, accumulation radar data and other measurements that contain information about any of the processes that are solved for.

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