Basal Mass Balance Along a Flow Line on Ronne Ice Shelf, Antarctica (Abstract)

Recent glaciological work on Ronne Ice Shelf has focused on an assumed flow line which extends from Rutford Ice Stream grounding line to the ice front. Results from doppler satellite surveying and radio echo-sounding are used in kinematic calculations to determine the basal mass balance, assuming the flow line to be in a steady state. Models suggest that basal melting dominates over most of the flow line and is most pronounced at the extremities. In the region within 300 km of the grounding line and over the final 45 km before the ice front, at least 1 m/a on average must melt away to maintain the observed velocity and thickness profile. More gentle melting occurs over about half the remaining distance, but in a region between 130 and 300 km in from the ice front, basal freezing must occur at an average rate of about 0.1 m/a to maintain a steady state. The existence of a thin layer of saline ice underlying the ice shelf, which persists for a further 80 km down-stream before being melted away entirely, is consistent with the weak returns observed during both airborne and ground-based radio echo-sounding in this region.

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Characteristics of Ice Flow in Marie Byrd Land, Antarctica

Journal of Glaciology ◽

10.3189/s0022143000014659 ◽

1979 ◽

Vol 24 (90) ◽

pp. 63-75 ◽

Cited By ~ 2

Author(s):

K. E. Rose

Keyword(s):

Flow Line ◽

Landsat Imagery ◽

Ice Sheet ◽

West Antarctica ◽

Ice Shelf ◽

Ice Streams ◽

Ice Flow ◽

Ross Ice Shelf ◽

Radio Echo Sounding ◽

Echo Sounding

AbstractExtensive radio echo-sounding has mapped the part of West Antarctica between Byrd Station, the Whitmore Mountains, the Transantarctic Mountains, and the Ross Ice Shelf. The ice sheet in this area is dominated by five major sub-parallel ice streams (A–E), which are up to 100 km wide and extend inland from the grounding line of the Ross Ice Shelf for about 400 km. Their positions have been determined by crevassing seen on radio echo-sounding records, trimetrogon photographs, and Landsat imagery. The ice streams are characterized by their flat transverse cross-sections, while the intervening ice sheet exhibits domes and ridges. Ice flow lines are defined from the ice-surface contour pattern and the trend of the ice streams. It is apparent from this work that the flow line passing through Byrd Station joins ice stream D.The bedrock of the area is relatively smooth near the Ross Ice Shelf, becoming rougher near Byrd Station and especially so near the Whitmore Mountains. Bedrock troughs, which control the positions of the ice streams, are believed to have a tectonic origin.In this paper the role of the ice streams in the glaciological regime of West Antarctica is investigated from radio-echo data and estimates of balance velocity, basal shear stress, and basal temperatures.

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Marine ice sheet model performance depends on basal sliding physics and sub-shelf melting

The Cryosphere ◽

10.5194/tc-11-319-2017 ◽

2017 ◽

Vol 11 (1) ◽

pp. 319-329 ◽

Cited By ~ 23

Author(s):

Rupert Michael Gladstone ◽

Roland Charles Warner ◽

Benjamin Keith Galton-Fenzi ◽

Olivier Gagliardini ◽

Thomas Zwinger ◽

...

Keyword(s):

Flow Line ◽

Ice Sheet ◽

Model Performance ◽

Effective Pressure ◽

Physical Processes ◽

Ice Shelf ◽

Grounding Line ◽

Basal Sliding ◽

Power Law Function ◽

Basal Melting

Abstract. Computer models are necessary for understanding and predicting marine ice sheet behaviour. However, there is uncertainty over implementation of physical processes at the ice base, both for grounded and floating glacial ice. Here we implement several sliding relations in a marine ice sheet flow-line model accounting for all stress components and demonstrate that model resolution requirements are strongly dependent on both the choice of basal sliding relation and the spatial distribution of ice shelf basal melting.Sliding relations that reduce the magnitude of the step change in basal drag from grounded ice to floating ice (where basal drag is set to zero) show reduced dependence on resolution compared to a commonly used relation, in which basal drag is purely a power law function of basal ice velocity. Sliding relations in which basal drag goes smoothly to zero as the grounding line is approached from inland (due to a physically motivated incorporation of effective pressure at the bed) provide further reduction in resolution dependence.A similar issue is found with the imposition of basal melt under the floating part of the ice shelf: melt parameterisations that reduce the abruptness of change in basal melting from grounded ice (where basal melt is set to zero) to floating ice provide improved convergence with resolution compared to parameterisations in which high melt occurs adjacent to the grounding line.Thus physical processes, such as sub-glacial outflow (which could cause high melt near the grounding line), impact on capability to simulate marine ice sheets. If there exists an abrupt change across the grounding line in either basal drag or basal melting, then high resolution will be required to solve the problem. However, the plausible combination of a physical dependency of basal drag on effective pressure, and the possibility of low ice shelf basal melt rates next to the grounding line, may mean that some marine ice sheet systems can be reliably simulated at a coarser resolution than currently thought necessary.

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Characteristics of Ice Flow in Marie Byrd Land, Antarctica

Journal of Glaciology ◽

10.1017/s0022143000014659 ◽

1979 ◽

Vol 24 (90) ◽

pp. 63-75 ◽

Cited By ~ 188

Author(s):

K. E. Rose

Keyword(s):

Flow Line ◽

Landsat Imagery ◽

Ice Sheet ◽

West Antarctica ◽

Ice Shelf ◽

Ice Streams ◽

Ice Flow ◽

Ross Ice Shelf ◽

Radio Echo Sounding ◽

Echo Sounding

AbstractExtensive radio echo-sounding has mapped the part of West Antarctica between Byrd Station, the Whitmore Mountains, the Transantarctic Mountains, and the Ross Ice Shelf. The ice sheet in this area is dominated by five major sub-parallel ice streams (A–E), which are up to 100 km wide and extend inland from the grounding line of the Ross Ice Shelf for about 400 km. Their positions have been determined by crevassing seen on radio echo-sounding records, trimetrogon photographs, and Landsat imagery. The ice streams are characterized by their flat transverse cross-sections, while the intervening ice sheet exhibits domes and ridges. Ice flow lines are defined from the ice-surface contour pattern and the trend of the ice streams. It is apparent from this work that the flow line passing through Byrd Station joins ice stream D.The bedrock of the area is relatively smooth near the Ross Ice Shelf, becoming rougher near Byrd Station and especially so near the Whitmore Mountains. Bedrock troughs, which control the positions of the ice streams, are believed to have a tectonic origin.In this paper the role of the ice streams in the glaciological regime of West Antarctica is investigated from radio-echo data and estimates of balance velocity, basal shear stress, and basal temperatures.

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Radio Echo-Sounding of Riiser-Larsenisen (Abstract only)

Annals of Glaciology ◽

10.3189/s0260305500003347 ◽

1982 ◽

Vol 3 ◽

pp. 355-355 ◽

Cited By ~ 2

Author(s):

Olav Orheim

Keyword(s):

Outer Part ◽

Ice Thickness ◽

Horizontal Distance ◽

Ice Shelf ◽

Ice Stream ◽

Grounding Line ◽

Radio Echo Sounding ◽

Polar Research Institute ◽

Antarctic Research ◽

Echo Sounding

The Norwegian Antarctic Research Expedition 1978–79 used the Scott Polar Research Institute Mk IV radio echo-sounding system fitted in a Bell 206B helicopter to survey 620 km of Riiser-Larsenisen and 100 km across the outer part of Stancomb-Wills Ice Stream. Observed thicknesses of Riiser-Larsenisen decrease from 700 m at the grounding line to less than 200 m at the ice front. The thickness of Bllenga ice rise varied between 200 and 450 m. The ice shelf thins towards the east, and seems there to flow obliquely to the ice front (Fig.1).Step-like change in thickness of >150 m over 500 m horizontal distance i s observed in the central part of the ice shelf. The records also demonstrate undulations in ice thickness of 600 to 700 m wavelength and 50 m amplitude, and various types of rifts and crevasses. Internal layering is recorded at 250 to 300 m depth over Blåenga and i n the ice shelf up-stream of this ice rise.Observed ice thicknesses on Stancomb-Wills Ice Stream range from 130 to 220 m, with no systematic decrease towards the ice front. The records include long sections of heavy scatter from densely spaced rifts and bottom crevasses. This ice stream attains velocities > 4 km a−1, and is much more active than Riiser-Larsenisen. This high activity has resulted in extensive fracturing of the ice shelf.

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Basal melting at the Ekström Ice Shelf, Antarctica, estimated from mass flux divergence

Annals of Glaciology ◽

10.3189/2012aog60a167 ◽

2012 ◽

Vol 53 (60) ◽

pp. 294-302 ◽

Cited By ~ 13

Author(s):

Niklas Neckel ◽

Reinhard Drews ◽

Wolfgang Rack ◽

Daniel Steinhage

Keyword(s):

Steady State ◽

Mass Flux ◽

Large Scale ◽

Snow Accumulation ◽

Ice Thickness ◽

Flux Divergence ◽

Ice Shelf ◽

Mass Fluxes ◽

Radio Echo Sounding ◽

Basal Melting

AbstractWe characterize the basal mass balance of the Ekström Ice Shelf, Dronning Maud Land, Antarctica, using interferometrically derived surface velocities and ice thickness measurements from radio-echo sounding (RES). The surface velocities are based on data from European Remote-sensing Satellites-1 and -2 (ERS-1/2) during 1994–97. The ice thickness grid consists of 136 RES profiles acquired between 1996 and 2006. Mass fluxes are calculated along selected RES profiles where possible, to reduce uncertainties from ice thickness interpolation. Elsewhere large-scale mass fluxes are calculated using interpolated ice thickness data. Themass flux into the Ekström Ice Shelf from the main grounded drainage basins is estimated to be 3.19±0.4Gt a–1. The mass flux near the ice shelf front is 2.67±0.3Gt a–1. Assuming steady state, and based on the equation of continuity, we interpret the residual mass flux as a combined effect of snow accumulation and subglacial melting/refreezing. Using net snow accumulation rates from previous studies, we link the mass flux divergence in irregular-shaped polygons to processes beneath the ice shelf. The highest subglacial melt rates of ~1.1ma–1 are found near the grounding zone of two main inflow glaciers, and around the German station Neumayer III. The detection of unlikely refreezing in a small area ~15 km west of Neumayer III is attributed to both dataset inaccuracies and a (possibly past) violation of the steady-state assumption. In general, the method and input data allow mapping of the spatial distribution of basal melting and the results are in good agreement with several previous studies.

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Radio Echo-Sounding of Riiser-Larsenisen (Abstract only)

Annals of Glaciology ◽

10.1017/s0260305500003347 ◽

1982 ◽

Vol 3 ◽

pp. 355 ◽

Cited By ~ 6

Author(s):

Olav Orheim

Keyword(s):

Outer Part ◽

Ice Thickness ◽

Horizontal Distance ◽

Ice Shelf ◽

Ice Stream ◽

Grounding Line ◽

Radio Echo Sounding ◽

Polar Research Institute ◽

Antarctic Research ◽

Echo Sounding

The Norwegian Antarctic Research Expedition 1978–79 used the Scott Polar Research Institute Mk IV radio echo-sounding system fitted in a Bell 206B helicopter to survey 620 km of Riiser-Larsenisen and 100 km across the outer part of Stancomb-Wills Ice Stream. Observed thicknesses of Riiser-Larsenisen decrease from 700 m at the grounding line to less than 200 m at the ice front. The thickness of Bllenga ice rise varied between 200 and 450 m. The ice shelf thins towards the east, and seems there to flow obliquely to the ice front (Fig.1). Step-like change in thickness of >150 m over 500 m horizontal distance i s observed in the central part of the ice shelf. The records also demonstrate undulations in ice thickness of 600 to 700 m wavelength and 50 m amplitude, and various types of rifts and crevasses. Internal layering is recorded at 250 to 300 m depth over Blåenga and i n the ice shelf up-stream of this ice rise. Observed ice thicknesses on Stancomb-Wills Ice Stream range from 130 to 220 m, with no systematic decrease towards the ice front. The records include long sections of heavy scatter from densely spaced rifts and bottom crevasses. This ice stream attains velocities > 4 km a−1, and is much more active than Riiser-Larsenisen. This high activity has resulted in extensive fracturing of the ice shelf.

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Basal melting along the floating part of Byrd Glacier

Antarctic Science ◽

10.1017/s0954102004002068 ◽

2004 ◽

Vol 16 (3) ◽

pp. 355-358 ◽

Cited By ~ 5

Author(s):

JAMES P. KENNEALLY ◽

TERENCE J. HUGHES

Keyword(s):

Mass Balance ◽

Velocity Data ◽

Ice Shelf ◽

Mass Balance Calculation ◽

Ross Ice Shelf ◽

Balance Calculation ◽

Grounding Line ◽

Basal Melting

A mass balance calculation was made for the floating part of Byrd Glacier, using 1978–79 ice elevation and velocity data, over the 45 km of Byrd Glacier from its grounding line to where it leaves its fjord and merges with the Ross Ice Shelf. Smoothed basal melting rates were relatively uniform over this distance and averaged 12 ± 2 m yr−1.

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Investigations of the mass balance of the southeastern Ronne Ice Shelf, Antarctica

Annals of Glaciology ◽

10.3189/172756499781820996 ◽

1999 ◽

Vol 29 ◽

pp. 250-254 ◽

Cited By ~ 8

Author(s):

A. Lambrecht ◽

C. Mayer ◽

H. Oerter ◽

U. Nixdorf

Keyword(s):

Mass Balance ◽

Mass Flux ◽

Ice Sheet ◽

Ice Thickness ◽

Ice Shelf ◽

Southeastern Part ◽

Ice Stream ◽

Grounding Line ◽

Radio Echo Sounding ◽

Stream Transport

AbstractData from the Filchner V Campaign were used to investigate the mass-balance conditions in the southeastern Ronne Ice Shelf (RIS), Antarctica. Radio-echo sounding and seismic measurements over this area show a maximum ice thickness of >2000 m close to the grounding line of Foundation Ice Stream. The measurements also revealed that the position of this grounding line is 40 km further south than previously thought. New mass-flux calculations result in an estimate of 51 km3 a−1 for the ice-stream transport from the ice sheet into the eastern ice shelf. The Mollereisstrom (MES), west of Foundation Ice Stream, shows a maximum ice thickness of 1100-1200 m in the grounding-line area and a mass flux of 23 km3 a−1.Assuming steady-state conditions, mass-balance calculations based on the new data result in a mean melt rate of about 1 ma−1 at the ice-shelf base for the entire southeastern part of the RIS. The melt rate in the grounding-line area of Foundation Ice Stream exceeds 9 m a−1. In contrast, other ice streams draining into the Filchner-Ronne Ice Shelf show maximum melt rates from 1-2 ma-1. (MES) to 4 ma−1 (Rutford Ice Stream). Our calculations indicate that nearly all of the ice deposited in the drainage area of the eastern RIS on the ice sheet does not reach the ice-shelf front as original meteoric ice, but is melted at the ice-shelf base.

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