Numerical modelling of geothermal heat flux and ice velocity influencing the thermal conditions of the Priestley Glacier trough (northern Victoria Land, Antarctica)

Geomorphology ◽  
2021 ◽  
Vol 394 ◽  
pp. 107959
Author(s):  
G.M. Marmoni ◽  
S. Martino ◽  
M.C. Salvatore ◽  
M. Gaeta ◽  
C. Perinelli ◽  
...  
Keyword(s):  
Heat Flux ◽  
Numerical Modelling ◽  
Thermal Conditions ◽  
Geothermal Heat ◽  
Victoria Land ◽  
Ice Velocity

scholarly journals Evaluation of six geothermal heat flux maps for the Antarctic Lambert-Amery glacial system

2021 ◽  
Author(s):  
Haoran Kang ◽  
Liyun Zhao ◽  
Michael Wolovick ◽  
John C. Moore
Keyword(s):  
Heat Flux ◽  
Frictional Heating ◽  
Thermal Conditions ◽  
Ice Shelf ◽  
Geothermal Heat ◽  
Glacier System ◽  
Amery Ice Shelf ◽  
Ice Sheet Dynamics ◽  
Subglacial Lakes ◽  
The Antarctic

Abstract. Basal thermal conditions play an important role in ice sheet dynamics, and they are sensitive to geothermal heat flux (GHF). Here we estimate the basal thermal conditions, including basal temperature, basal melt rate, and friction heat underneath the Lambert-Amery glacier system in east Antarctica, using a combination of a forward model and an inversion from a 3D ice flow model. We assess the sensitivity and uncertainty of basal thermal conditions using six different GHFs. We evaluate the modelled results using all available observed subglacial lakes. There are very large differences in modelled spatial pattern of temperate basal conditions using the different GHFs. The two most-recent GHF fields inverted from aerial geomagnetic observations have higher values of GHF in the region, produce a larger warm-based area, and match the observed subglacial lakes better than the other GHFs. The fast flowing glacier region has a lower modelled basal friction coefficient, faster basal velocity, with higher basal frictional heating in the range of 50–2000 mW m−2 than the base under slower flowing glaciated areas. The modelled basal melt rate reaches ten to hundreds of mm per year locally in Lambert, Lepekhin and Kronshtadtskiy glaciers feeding the Amery ice shelf, and ranges from 0–5 mm yr−1 on the temperate base of the vast inland region.

scholarly journals Sensitivity of the frozen/melted basal boundary to perturbations of basal traction and geothermal heat flux: Isunnguata Sermia, western Greenland

2011 ◽  
Vol 52 (59) ◽  
pp. 43-50 ◽  
Author(s):  
Douglas J. Brinkerhoff ◽  
Toby W. Meierbachtol ◽  
Jesse V. Johnson ◽  
Joel T. Harper
Keyword(s):  
Heat Flux ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Thermal Conditions ◽  
Two Dimensional ◽  
Adjoint Model ◽  
The West ◽  
Geothermal Heat ◽  
Coupled Numerical Model ◽  
The Difference

AbstractA full-stress, thermomechanically coupled, numerical model is used to explore the interaction between basal thermal conditions and motion of a terrestrially terminating section of the west Greenland ice sheet. The model domain is a two-dimensional flowline profile extending from the ice divide to the margin. We use data-assimilation techniques based on the adjoint model in order to optimize the basal traction field, minimizing the difference between modeled and observed surface velocities. We monitor the sensitivity of the frozen/melted boundary (FMB) to changes in prescribed geothermal heat flux and sliding speed by applying perturbations to each of these parameters. The FMB shows sensitivity to the prescribed geothermal heat flux below an upper threshold where a maximum portion of the bed is already melted. The position of the FMB is insensitive to perturbations applied to the basal traction field. This insensitivity is due to the short distances over which longitudinal stresses act in an ice sheet.

The effect of geothermal heat flux on the deglacial evolution of the Greenland ice sheet

2021 ◽  
Author(s):  
Parviz Ajourlou ◽  
François PH Lapointe ◽  
Glenn A Milne ◽  
Yasmina Martos
Keyword(s):  
Boundary Condition ◽  
Heat Flux ◽  
Thermal State ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Sampling Procedure ◽  
Geophysical Research ◽  
Geothermal Heat ◽  
Input Field ◽  
Uncertainty Estimates

<p>Geothermal heat flux (GHF) is known to be an important control on the basal thermal state of an ice sheet which, in turn, is a key factor in governing how the ice sheet will evolve in response to a given climate forcing. In recent years, several studies have estimated GHF beneath the Greenland ice sheet using different approaches (e.g. Rezvanbehbahani et al., Geophysical Research Letters, 2017; Martos et al., Geophysical Research Letters, 2018; Greve, Polar Data Journal, 2019). Comparing these different estimates indicates poor agreement and thus large uncertainty in our knowledge of this important boundary condition for modelling the ice sheet. The primary aim of this study is to quantify the influence of this uncertainty on modelling the past evolution of the ice sheet with a focus on the most recent deglaciation. We build on past work that considered three GHF models (Rogozhina et al., 2011) by considering over 100 different realizations of this input field. We use the uncertainty estimates from Martos et al. (Geophysical Research Letters, 2018) to generate GHF realisations via a statistical sampling procedure. A sensitivity analysis using these realisations and the Parallel Ice Sheet Model (PISM, Bueler and Brown, Journal of Geophysical Research, 2009) indicates that uncertainty in GHF has a dramatic impact on both the volume and spatial distribution of ice since the last glacial maximum, indicating that more precise constraints on this boundary condition are required to improve our understanding of past ice sheet evolution and, consequently, reduce uncertainty in future projections.</p>

Firefighter Equipment Operational Environment: Evaluation of Thermal Conditions

2017 ◽  
Author(s):  
Daniel Madrzykowski ◽  
Keyword(s):  
Heat Flux ◽  
Thermal Performance ◽  
Protective Clothing ◽  
Thermal Conditions ◽  
Gas Temperature ◽  
Gas Velocity ◽  
Hot Gas ◽  
Performance Requirements ◽  
Fire Environment ◽  
Fire Ground

The goal of this study was to review the available literature to develop a quantitative description of the thermal conditions firefighters and their equipment are exposed to in a structural fire environment. The thermal exposure from the modern fire environment was characterized through the review of fire research studies and fire-ground incidents that provided insight and data to develop a range of quantification. This information was compared with existing standards for firefighting protective equipment to generate a sense of the gap between known information and the need for improved understanding. The comparison of fire conditions with the thermal performance requirements of firefighter protective gear and equipment demonstrates that a fire in a compartment can generate conditions that can fail the equipment that a firefighter wears or uses. The review pointed out the following: 1. The accepted pairing of gas temperature ranges with a corresponding range of heat fluxes does not reflect all compartment fire conditions. There are cases in which the heat flux exceeds the hazard level of the surrounding gas temperature. 2. Thermal conditions can change within seconds. Experimental conditions and incidents were identified in which firefighters would be operating in thermal conditions that were safe for operation based on the temperature and heat flux, but then due to a change in the environment the firefighters would be exposed to conditions that could exceed the protective capabilities of their PPE. 3. Gas velocity is not explicitly considered within the thermal performance requirements. Clothing and equipment tested with a hot air circulating (convection) oven are exposed to gas velocities that measure approximately 1.5 m/s (3 mph). In contrast, the convected hot gas flows within a structure fire could range from 2.3 m/s (5 mph) to 7.0 m/s (15 mph). In cases where the firefighter or equipment would be located in the exhaust portion of a flow path, while operating above the level of the fire, the hot gas velocity could be even higher. This increased hot gas velocity would serve to increase the convective heat transfer rate to the equipment and the firefighter, thereby reducing the safe operating time within the structure. 4. Based on the limited data available, it appears currently available protective clothing enables firefighters to routinely operate in conditions above and beyond the "routine" conditions measured in the fire-ground exposure studies conducted during the 1970s. The fire service and fire standards communities could benefit from an improved understanding of: • real world fire-ground conditions, including temperatures, heat flux, pressure, and chemical exposures; • the impact of convection on the thermal resistance capabilities of firefighting PPE and equipment; and • the benefits of balancing the thermal exposures (thermal performance requirements) across different components of firefighter protective clothing and safety equipment. Because it is unlikely due to trade offs in weight, breathe-ability, usability, cost, etc., that fireproof PPE and equipment will ever be a reality, fire officers and fire chiefs need to consider the capabilities of the protection that their firefighters have when determining fire attack strategies and tactics to ensure that the PPE and equipment is kept within its design operating environment, and that the safety buffer it provides is maintained.

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 Coupled Northern Hemisphere permafrost–ice-sheet evolution over the last glacial cycle

2015 ◽  
Vol 11 (9) ◽  
pp. 1165-1180 ◽  
Author(s):  
M. Willeit ◽  
A. Ganopolski
Keyword(s):  
Heat Flux ◽  
Northern Hemisphere ◽  
Ice Sheet ◽  
The Arctic ◽  
Sediment Layer ◽  
Glacial Cycle ◽  
Geothermal Heat ◽  
Climate History ◽  
Last Glacial ◽  
The Last Glacial

Abstract. Permafrost influences a number of processes which are relevant for local and global climate. For example, it is well known that permafrost plays an important role in global carbon and methane cycles. Less is known about the interaction between permafrost and ice sheets. In this study a permafrost module is included in the Earth system model CLIMBER-2, and the coupled Northern Hemisphere (NH) permafrost–ice-sheet evolution over the last glacial cycle is explored. The model performs generally well at reproducing present-day permafrost extent and thickness. Modeled permafrost thickness is sensitive to the values of ground porosity, thermal conductivity and geothermal heat flux. Permafrost extent at the Last Glacial Maximum (LGM) agrees well with reconstructions and previous modeling estimates. Present-day permafrost thickness is far from equilibrium over deep permafrost regions. Over central Siberia and the Arctic Archipelago permafrost is presently up to 200–500 m thicker than it would be at equilibrium. In these areas, present-day permafrost depth strongly depends on the past climate history and simulations indicate that deep permafrost has a memory of surface temperature variations going back to at least 800 ka. Over the last glacial cycle permafrost has a relatively modest impact on simulated NH ice sheet volume except at LGM, when including permafrost increases ice volume by about 15 m sea level equivalent in our model. This is explained by a delayed melting of the ice base from below by the geothermal heat flux when the ice sheet sits on a porous sediment layer and permafrost has to be melted first. Permafrost affects ice sheet dynamics only when ice extends over areas covered by thick sediments, which is the case at LGM.

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.

Sign in / Sign up

Export Citation Format

Share Document