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 A Subglacial Lake in Antarctica Churns Out Nutrients

Eos ◽  
2020 ◽  
Vol 101 ◽  
Author(s):  
Katherine Kornei
Keyword(s):  
Organic Carbon ◽  
Food Chain ◽  
Ice Sheet ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Subglacial Lake ◽  
West Antarctic ◽  
Subglacial Lake Whillans

Eight hundred meters below the West Antarctic Ice Sheet, microbes in subglacial Lake Whillans create organic carbon that helps power the Southern Ocean’s vast food chain.

scholarly journals Distribution of basal melting and freezing beneath tributaries of Ice Stream C: implication for the Holocene decay of the West Antarctic ice sheet

2003 ◽  
Vol 36 ◽  
pp. 273-282 ◽  
Author(s):  
Stefan W. Vogel ◽  
Slawek Tulaczyk ◽  
Ian R. Joughin
Keyword(s):  
Ice Sheet ◽  
Ice Streams ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
The Holocene ◽  
West Antarctic ◽  
Basal Ice ◽  
Ice Stream ◽  
Basal Melting

AbstractIce-stream tributaries connect the relatively slow-moving interior of the West Antarctic ice sheet (WAIS) with the fast-flowing Siple Coast ice streams. Basal water underneath these ice streams reduces basal resistance and enables the fast motion of the ice. Basal melting being the only source for this water, it is important to include the distribution of basal melting and freezing into numerical models assessing the stability of the WAIS. However, it is very difficult to constrain its distribution from existing field observations. Past borehole observations confirmed the presence of a wet bed at Byrd Station in the WAIS interior and at different locations within Siple Coast ice streams. However, the recent discovery of a 12–25m thick sediment-laden bubble-free basal ice layer at the UpC boreholes indicates that basal freezing is either currently occurring or had occurred upstream during the last glacial–interglacialcycle.We use a flowline model of ice thermodynamics to assess and quantify the spatial and temporal distribution of basal melting and freezing beneath Ice Stream C tributaries, taking into account the geothermal flux, shear heating and heat conduction away from the bed. Under the assumption that the ice was moving over a weak bed (τb =1–10 kPa) our model is able to reproduce a layer of frozen-on ice similar in thickness to the UpC “sticky spot” basal ice layer. Increased basal melting in the early Holocene possibly could have initiated the Holocene decay of the WAIS, whereas increased freezing rates over the past few thousand years could have decreased the amount of basal water in the system, resulting in a strengthening of the bed. This is consistent with current force-budget calculations for ice-stream tributaries and with observed stoppages and slow-downs of ice streams.

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.

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.

scholarly journals Monitoring changes of the Antarctic Ice sheet by GRACE, ICESat and GNSS

2019 ◽  
Vol 49 (4) ◽  
pp. 403-424
Author(s):  
Fang Zou ◽  
Robert Tenzer ◽  
Samurdhika Rathnayake
Keyword(s):  
Mass Loss ◽  
Ice Sheet ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Ice Volume ◽  
West Antarctic ◽  
Elevation Changes ◽  
A Minor ◽  
The Antarctic

Abstract In this study, we estimate the ice mass changes, the ice elevation changes and the vertical displacements in Antarctica based on analysis of multi-geodetic datasets that involve the satellite gravimetry (GRACE), the satellite altimetry (ICESat) and the global navigation satellite systems (GNSS). According to our estimates, the total mass change of the Antarctic ice sheet from GRACE data is −162.91 Gt/yr over the investigated period between April 2002 and June 2017. This value was obtained after applying the GIA correction of −98.12 Gt/yr derived from the ICE-5G model of the glacial iso-static adjustment. A more detailed analysis of mass balance changes for three individual drainage regions in Antarctica reveal that the mass loss of the West Antarctic ice sheet was at a rate of −143.11 Gt/yr. The mass loss of the Antarctic Peninsula ice sheet was at a rate of −24.31 Gt/yr. The mass of the East Antarctic ice sheet increased at a rate of 5.29 Gt/yr during the investigated period. When integrated over the entire Antarctic ice sheet, average rates of ice elevation changes over the period from March 2003 to October 2009 derived from ICESat data represent the loss of total ice volume of −155.6 km3.The most prominent features in ice volume changes in Antarctica are characterized by a strong dynamic thinning and ice mass loss in the Amundsen Sea Embayment that is part of the West Antarctic ice sheet. In contrast, coastal regions between Dronning Maud Land and Enderby Land exhibit a minor ice increase, while a minor ice mass loss is observed in Wilkes Land. The vertical load displacement rates estimated from GRACE and GPS data relatively closely agree with the GIA model derived based on the ice-load history and the viscosity profile. For most sites, the GRACE signal appears to be in phase and has the same amplitude as that obtained from the GPS vertical motions while other sites exhibit some substantial differences possibly attributed to thermo-elastic deformations associated with surface temperature.

scholarly journals A microbial ecosystem beneath the West Antarctic ice sheet

Nature ◽  
2014 ◽  
Vol 512 (7514) ◽  
pp. 310-313 ◽  
Author(s):  
Brent C. Christner ◽  
◽  
John C. Priscu ◽  
Amanda M. Achberger ◽  
Carlo Barbante ◽  
...  
Keyword(s):  
Ice Sheet ◽  
The West ◽  
Microbial Ecosystem ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic

Deglacial history of the West Antarctic Ice Sheet in the Weddell Sea embayment: Constraints on past ice volume change

Geology ◽  
2010 ◽  
Vol 38 (5) ◽  
pp. 411-414 ◽  
Author(s):  
Michael J. Bentley ◽  
Christopher J. Fogwill ◽  
Anne M. Le Brocq ◽  
Alun L. Hubbard ◽  
David E. Sugden ◽  
...  
Keyword(s):  
Volume Change ◽  
Ice Sheet ◽  
Weddell Sea ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Ice Volume ◽  
West Antarctic ◽  
History Of
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