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 Radio-echo sounding of the lambert glacier basin

1975 ◽  
Vol 15 (73) ◽  
pp. 103-111 ◽  
Author(s):  
V. I. Morgan ◽  
W. F. Budd
Keyword(s):  
Surface Topography ◽  
Sea Level ◽  
Drainage Basin ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Deep Trench ◽  
Glacier System ◽  
Amery Ice Shelf ◽  
Lambert Glacier ◽  
Echo Sounding

AbstractSeveral seasons of aerial ice-thickness soundings over the region of the Prince Charles Mountains, the Lambert Glacier system, the Amery Ice Shelf, and their drainage basin in east Antarctica have now been completed. The measurements provide detailed maps of surface topography and ice thickness over an area of about 2 X 105 km2. The equipment used consisted of a 100 MHz echo sounder designed and constructed by Antarctic Division and carried in a Pilatus Porter aircraft. ERTS imagery provides a valuable background for portraying the echo-sounding results. These results show that an extensive, deep subglacial valley system forms the basis of the large drainage basin with concave ice surface topography which channels the ice flow into the Amery Ice Shelf. Deep glacial streams penetrate a long way into the ice-sheet basin. The rock relief is considerable, varying from 3 000 m above (present) sea-level to 2 000 m below sea-level. A very deep subglacial trench exists in the region of the confluence of the Fisher, Mellor, and Lambert Glaciers where the ice thickness reaches 2 500 m. The low surface slope and high ice velocity are suggestive of high melt production in this region. The strong echo, together with the high bedrock back-slope, suggests that the deep trench may contain a basal melt lake.

scholarly journals Downslope föhn winds over the Antarctic Peninsula and their effect on the Larsen ice shelves

2014 ◽  
Vol 14 (18) ◽  
pp. 9481-9509 ◽  
Author(s):  
D. P. Grosvenor ◽  
J. C. King ◽  
T. W. Choularton ◽  
T. Lachlan-Cope
Keyword(s):  
Heat Flux ◽  
Wind Speed ◽  
Surface Energy ◽  
Antarctic Peninsula ◽  
Energy Budget ◽  
Surface Flux ◽  
Surface Energy Budget ◽  
Ice Shelf ◽  
Aircraft Observations ◽  
The Antarctic

Abstract. Mesoscale model simulations are presented of a westerly föhn event over the Antarctic Peninsula mountain ridge and onto the Larsen C ice shelf, just south of the recently collapsed Larsen B ice shelf. Aircraft observations showed the presence of föhn jets descending near the ice shelf surface with maximum wind speeds at 250–350 m in height. Surface flux measurements suggested that melting was occurring. Simulated profiles of wind speed, temperature and wind direction were very similar to the observations. However, the good match only occurred at a model time corresponding to ~9 h before the aircraft observations were made since the model föhn jets died down after this. This was despite the fact that the model was nudged towards analysis for heights greater than ~1.15 km above the surface. Timing issues aside, the otherwise good comparison between the model and observations gave confidence that the model flow structure was similar to that in reality. Details of the model jet structure are explored and discussed and are found to have ramifications for the placement of automatic weather station (AWS) stations on the ice shelf in order to detect föhn flow. Cross sections of the flow are also examined and were found to compare well to the aircraft measurements. Gravity wave breaking above the mountain crest likely created a~situation similar to hydraulic flow and allowed föhn flow and ice shelf surface warming to occur despite strong upwind blocking, which in previous studies of this region has generally not been considered. Our results therefore suggest that reduced upwind blocking, due to wind speed increases or stability decreases, might not result in an increased likelihood of föhn events over the Antarctic Peninsula, as previously suggested. The surface energy budget of the model during the melting periods showed that the net downwelling short-wave surface flux was the largest contributor to the melting energy, indicating that the cloud clearing effect of föhn events is likely to be the most important factor for increased melting relative to non-föhn days. The results also indicate that the warmth of the föhn jets through sensible heat flux ("SH") may not be critical in causing melting beyond boundary layer stabilisation effects (which may help to prevent cloud cover and suppress loss of heat by convection) and are actually cancelled by latent heat flux ("LH") effects (snow ablation). It was found that ground heat flux ("GRD") was likely to be an important factor when considering the changing surface energy budget for the southern regions of the ice shelf as the climate warms.

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 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 Amery Ice Shelf and its hinterland

Polar Record ◽  
1960 ◽  
Vol 10 (64) ◽  
pp. 30-34 ◽  
Author(s):  
Malcolm Mellor ◽  
Graeme McKinnon
Keyword(s):  
Prydz Bay ◽  
Ice Shelf ◽  
Amery Ice Shelf ◽  
Antarctic Research ◽  
Lambert Glacier ◽  
The Antarctic

During the thirty years since the Amery Ice Shelf was first sighted there has been a steady accumulation of information, first on the ice shelf itself and later on the interesting mountains and glacier systems which lie to its south. The ice shelf occupies the head of a large embayment consisting of Prydz Bay and Mackenzie Bay, which deeply indents the coastline of the Antarctic mainland near the borders of MacRobertson Land and Princess Elizabeth Land. An associated valley runs south from the bay, between the Prince Charles Mountains and the Mawson Escarpment, and it is occupied by one of the world's largest valley glaciers, the Lambert Glacier. (In fact, recent findings by Soviet parties suggest that the Lambert Glacier is considerably longer than the Beardmore Glacier.) The exploration, survey and subsequent mapping of the ice shelf, and the mountains and glaciers of its hinterland, by Australian National Antarctic Research Expeditions in recent years has been a major contribution to Antarctic geography.

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 The Dynamics of the Antarctic Ice Sheet

1989 ◽  
Vol 12 ◽  
pp. 16-22 ◽  
Author(s):  
W.F. Budd ◽  
D. Jenssen
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Accumulation Rate ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Surface Velocity ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
The Past ◽  
The Antarctic

A three-dimensional dynamic, thermodynamic ice-sheet model has been developed to simulate the past, present, and future behaviour of the Antarctic ice sheet. The present ice velocities depend on the deep ice temperatures which in turn depend on the past changes of the ice sheet, including surface temperature, accumulation rate, and ice thickness. The basal temperatures are also strongly dependent on the geothermal heat flux. The model has therefore been used to study the effect on the basal temperatures, of changes to the geothermal heat flux, as well as the past changes of surface temperature and accumulation rate based on results obtained from the Vostok deep ice core. The model is also used to compute the distribution of surface velocity required to balance the present accumulation rate and the dynamics velocity based on the stress, temperature, and flow properties of ice, for the internal deformation, plus a component due to ice sliding. These velocities are compared to observed surface velocities in East Antarctica to assess the state of balance and the performance of the dynamics formulation.

scholarly journals From ice-shelf tributary to tidewater glacier: continued rapid recession, acceleration and thinning of Röhss Glacier following the 1995 collapse of the Prince Gustav Ice Shelf, Antarctic Peninsula

2011 ◽  
Vol 57 (203) ◽  
pp. 397-406 ◽  
Author(s):  
N.F. Glasser ◽  
T.A. Scambos ◽  
J. Bohlander ◽  
M. Truffer ◽  
E. Pettit ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Satellite Image ◽  
Ice Shelf ◽  
Tidewater Glaciers ◽  
Speed Increase ◽  
Glacier System ◽  
Digital Elevation ◽  
Tidewater Glacier ◽  
Before And After ◽  
The Antarctic

AbstractWe use optical (ASTER and Landsat) and radar (ERS-1 and ERS-2) satellite imagery to document changes in the Prince Gustav Ice Shelf, Antarctic Peninsula, and its tributary glaciers before and after its January 1995 collapse. The satellite image record captures the transition from an ice-shelf glacier system to a tidewater glacial system and the subsequent rapid retreat and inferred ‘fatal’ negative mass balances that occur as lower glacier elevations lead to higher ablation and tidewater-style calving collapse. Pre-1995 images show that the central ice shelf was fed primarily by Sjögren Glacier flowing from the Antarctic Peninsula and by Röhss Glacier flowing from James Ross Island. Numerous structural discontinuities (rifts and crevasses) and melt ponds were present on the ice shelf before the collapse. After the ice shelf collapsed, Röhss Glacier retreated rapidly, becoming a tidewater glacier in 2002 and receding a total of ∼15 km between January 2001 and March 2009, losing >70% of its area. Topographic profiles of Röhss Glacier from ASTER-derived digital elevation models show a thinning of up to ∼150 m, and surface speeds increased up to ninefold (0.1–0.9 m d−1) over the same period. The rates of speed increase and elevation loss, however, are not monotonic; both rates slowed between late 2002 and 2005, accelerated in 2006 and slowed again in 2008–09. We conclude that tributary glaciers react to ice-shelf removal by rapid (if discontinuous) recession, and that the response of tidewater glaciers on the Antarctic Peninsula to ice-shelf removal occurs over timescales ranging from sub-annual to decadal.

On the modified Circumpolar Deep Water upwelling over the Four Ladies Bank in Prydz Bay, East Antarctica

2020 ◽  
Author(s):  
Chengyan Liu ◽  
Zhaomin Wang ◽  
Chen Cheng ◽  
Xi Liang ◽  
Yang Wu ◽  
...  
Keyword(s):  
Heat Flux ◽  
Standard Deviation ◽  
Kinetic Energy ◽  
Potential Temperature ◽  
Weddell Sea ◽  
East Antarctica ◽  
Prydz Bay ◽  
Ice Shelf ◽  
Borehole Data ◽  
Amery Ice Shelf

<p>We report on mooring observations of tidal currents in Prydz Bay, East Antarctica. Tides in Prydz Bay are mixed diurnal-semidiurnal and much weaker than that in the Ross Sea and the Weddell Sea, with the spatial and temporal averaged value of 2.58 cm s<sup>-1</sup> for all the current meter observations over the continental shelf. The major axes of the tidal ellipses are generally aligned south-north, probably steered by the topography. The tidal phases are modulated by both the baroclinic and barotropic tidal components. The averaged tidal kinetic energy can account for a fraction of ~13% with respect to the total kinetic energy at the Amery Ice Shelf calving front during the observing period. The long-term average tidal heat flux across the Amery Ice Shelf calving front is negligible, but the ratio of the tidal heat flux standard deviation to the residual heat flux standard deviation can be up to 41%. We also report on borehole observations of tide-like pulsing of potential temperature and salinity, indicating the indispensable tidal influences in the ice-ocean boundary layer. These mooring and borehole data support that the tidal processes should be highlighted in the investigations of the interaction between the Amery Ice Shelf and ocean.</p>

Sign in / Sign up

Export Citation Format

Share Document