Antarctic ice sheet thickness estimation using the horizontal-to-vertical spectral ratio method with single-station seismic ambient noise

Abstract. We report on a successful application of the horizontal-to-vertical spectral ratio (H / V) method, generally used to investigate the subsurface velocity structures of the shallow crust, to estimate the Antarctic ice sheet thickness for the first time. Using three-component, five-day long, seismic ambient noise records gathered from more than 60 temporary seismic stations located on the Antarctic ice sheet, the ice thickness measured at each station has comparable accuracy to the Bedmap2 database. Preliminary analysis revealed that 60 out of 65 seismic stations on the ice sheet obtained clear peak frequencies (f0) related to the ice sheet thickness in the H / V spectrum. Thus, assuming that the isotropic ice layer lies atop a high velocity half-space bedrock, the ice sheet thickness can be calculated by a simple approximation formula. About half of the calculated ice sheet thicknesses were consistent with the Bedmap2 ice thickness values. To further improve the reliability of ice thickness measurements, two-type models were built to fit the observed H / V spectrum through non-linear inversion. The two-type models represent the isotropic structures of single- and two-layer ice sheets, and the latter depicts the non-uniform, layered characteristics of the ice sheet widely distributed in Antarctica. The inversion results suggest that the ice thicknesses derived from the two-layer ice models were in good concurrence with the Bedmap2 ice thickness database, and that ice thickness differences between the two were within 300 m at almost all stations. Our results support previous finding that the Antarctic ice sheet is stratified. Extensive data processing indicates that the time length of seismic ambient noise records can be shortened to two hours for reliable ice sheet thickness estimation using the H / V method. This study extends the application fields of the H / V method and provides an effective and independent way to measure ice sheet thickness in Antarctica.

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Antarctic ice sheet thickness estimation using the H/V spectral ratio method with single-station seismic ambient noise

10.5194/tc-2017-164 ◽

2017 ◽

Author(s):

Peng Yan ◽

Zhiwei Li ◽

Fei Li ◽

Yuande Yang ◽

Weifeng Hao ◽

...

Keyword(s):

Ambient Noise ◽

Ice Sheet ◽

Sheet Thickness ◽

Spectral Ratio ◽

Ice Thickness ◽

Antarctic Ice Sheet ◽

Seismic Stations ◽

Thickness Estimation ◽

Seismic Ambient Noise ◽

The Antarctic

Abstract. The horizontal-to-vertical spectral ratio (H/V) method implemented at single stations using seismic ambient noise waveforms is a fast, noninvasive, efficient method to investigate the subsurface velocity structures of the shallow crust. In this study, we report on a successful application of the H/V method to estimate the Antarctic ice sheet thickness for the first time. Using three-component, five-day long, seismic ambient noise records gathered from more than 60 temporary seismic stations located on the Antarctic ice sheet, the ice thickness at each station was reliably measured. Preliminary analysis revealed that 60 out of 65 seismic stations on the ice sheet obtained clear peak frequencies (f0) related to the ice sheet thickness in the H/V spectrum. Thus, assuming that the isotropic ice layer lies atop a high velocity half-space bedrock, the ice sheet thickness can be calculated by a simple approximation formula. About half of the calculated ice sheet thickness were consistent with the Bedmap2 ice thickness values. To further improve the reliability of ice thickness measurements, two-type models were built to fit the observed H/V spectrum through non-linear inversion. The two-type models represent the isotropic structures of single and two-layer ice sheet, and the latter depicts the non-uniform, layered characteristics of the ice sheet widely distributed in Antarctica. The inversion results suggest that the ice thicknesses derived from the two-layer ice models were highly consistent with the Bedmap2 ice thickness database, and their ice thickness differences were within 300 m at almost all stations. Our results support previous finding that the Antarctic ice sheet is stratified. Extensive data processing indicates that the time length of seismic ambient noise records can be shortened to 1–2 hours for reliable ice sheet thickness estimation using the H/V method. This study extends the application fields of the H/V method and provides a complementary and independent way to measure ice sheet thickness in Antarctica.

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Review of "Antarctic ice sheet thickness estimation using the H/V spectral ratio method with single-station seismic ambient noise"

10.5194/tc-2017-164-rc1 ◽

2017 ◽

Author(s):

Andreas Köhler

Keyword(s):

Ambient Noise ◽

Ice Sheet ◽

Sheet Thickness ◽

Spectral Ratio ◽

Ratio Method ◽

Antarctic Ice Sheet ◽

Thickness Estimation ◽

Seismic Ambient Noise ◽

Single Station ◽

Spectral Ratio Method

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Review of Yan et al., “Antarctic ice sheet thickness estimation using the H/V spectral ratio method with single-station ambient noise”.

10.5194/tc-2017-164-rc2 ◽

2017 ◽

Author(s):

Adam Booth

Keyword(s):

Ambient Noise ◽

Ice Sheet ◽

Sheet Thickness ◽

Spectral Ratio ◽

Ratio Method ◽

Antarctic Ice Sheet ◽

Thickness Estimation ◽

Single Station ◽

Spectral Ratio Method

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Supplementary material to "Antarctic ice sheet thickness estimation using the H/V spectral ratio method with single-station seismic ambient noise"

10.5194/tc-2017-164-supplement ◽

2017 ◽

Author(s):

Peng Yan ◽

Zhiwei Li ◽

Fei Li ◽

Yuande Yang ◽

Weifeng Hao ◽

...

Keyword(s):

Ambient Noise ◽

Sheet Thickness ◽

Spectral Ratio ◽

Ratio Method ◽

Antarctic Ice Sheet ◽

Thickness Estimation ◽

Seismic Ambient Noise ◽

Single Station ◽

Supplementary Material ◽

Spectral Ratio Method

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Uncertainties in mass balance estimation of the Antarctic Ice Sheet using the input and output method

10.5194/tc-2021-325 ◽

2021 ◽

Author(s):

Yijing Lin ◽

Yan Liu ◽

Zhitong Yu ◽

Xiao Cheng ◽

Qiang Shen ◽

...

Keyword(s):

Mass Balance ◽

Scale Effect ◽

Ice Sheet ◽

Ice Thickness ◽

Clear Understanding ◽

Antarctic Ice Sheet ◽

Grounding Line ◽

Ice Velocity ◽

The Antarctic ◽

The Impact

Abstract. The input-output method (IOM) is one of the most popular methods of estimating the ice sheet mass balance (MB), with a significant advantage in presenting the dynamics response of ice to climate change. Assessing the uncertainties of the MB estimation using the IOM is crucial to gaining a clear understanding of the Antarctic ice-sheet mass budget. Here, we introduce a framework for assessing the uncertainties in the MB estimation due to the methodological differences in the IOM, the impact of the parameterization and scale effect on the modeled surface mass balance (SMB, input), and the impact of the uncertainties of ice thickness, ice velocity, and grounding line data on ice discharge (D, output). For the assessment of the D’s uncertainty, we present D at a fine scale. Compared with the goal of determining the Antarctic MB within an uncertainty of 15 Gt yr−1, we found that the different strategies employed in the methods cause considerable uncertainties in the annual MB estimation. The uncertainty of the RACMO2.3 SMB caused by its parameterization can reach 20.4 Gt yr−1, while that due to the scale effect is up to 216.7 Gt yr−1. The observation precisions of the MEaSUREs InSAR-based velocity (1–17 m yr−1), the airborne radio-echo sounder thickness (±100 m), and the MEaSUREs InSAR-based grounding line (±100 m) contribute uncertainties of 17.1 Gt yr−1, 10.5 ± 2.7 Gt yr−1 and 8.0~27.8 Gt yr−1 to the D, respectively. However, the D’s uncertainty due to the remarkable ice thickness data gap, which is represented by the thickness difference between the BEDMAP2 and the BedMachine reaches 101.7 Gt yr−1, which indicates its dominant cause of the future D’s uncertainty. In addition, the interannual variability of D caused by the annual changes in the ice velocity and ice thickness are considerable compared with the target uncertainty of 15 Gt yr−1, which cannot be ignored in annual MB estimations.

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Large-Scale Numerical Modelling of the Antarctic Ice Sheet

Annals of Glaciology ◽

10.1017/s0260305500002500 ◽

1982 ◽

Vol 3 ◽

pp. 42-49 ◽

Cited By ~ 54

Author(s):

W.F. Budd ◽

I.N. Smith

Keyword(s):

Sea Level ◽

Large Scale ◽

Accumulation Rate ◽

Ice Sheet ◽

Ice Thickness ◽

Ice Flow ◽

Antarctic Ice Sheet ◽

Flow Parameters ◽

The Antarctic ◽

Thinning Rate

A large-scale dynamic numerical model of the Antarctic ice sheet has been developed to study its present state of ice flow and mass balance as well as its response to long-term changes of climate or sea-level.The flow of ice over a two-dimensional grid is determined from the ice thickness, the basal shear stress, the bedrock depth, and ice flow parameters derived from velocities of existing ice sheets. The change in ice thickness with time is governed by the continuity equation involving the ice flux divergence and the ice accumulation or ablation. At the ice sheet seaward boundary, a floating criterion and floating ice thinning rate apply. Bedrock depression with a time-delayed response dependent on the history of the ice load is also included.A 61 × 61 point grid with 100 km spacing has been used to represent the ice-sheet surface, bedrock, and accumulation rate. The model has been used to simul a te the growth of the present ice sheet and i ts reaction to changes of sea-level, bedrock depression, accumulation rate, ice flow parameters, and the iceshelf thinning rate.Preliminary results suggest that the present ice sheet is not in equilibrium but rather is still adjusting to changes of these parameters.

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Geometric boundary conditions for modelling the velocity field of the Antarctic ice sheet

Annals of Glaciology ◽

10.1017/s0260305500013653 ◽

1996 ◽

Vol 23 ◽

pp. 364-373 ◽

Cited By ~ 32

Author(s):

Jonathan L. Bamber ◽

Philippe Huybrechts

Keyword(s):

Velocity Field ◽

Boundary Conditions ◽

Ice Sheet ◽

Surface Elevation ◽

Surface Velocity ◽

Ice Thickness ◽

Antarctic Ice Sheet ◽

Surface Slopes ◽

Geometric Boundary ◽

The Antarctic

This paper presents improved geometric boundary conditions (surface elevation and ice thickness) required as inputs to calculations of the surface-velocity field for the Antarctic ice sheet. A comparison of the two-dimensional horizontal velocity field obtained on the basis of conservation of mass (balance velocity) with the diagnostic velocity field calculated with an ice-sheet model (dynamic velocity) may yield information on shortcomings in the way the ice-sheet model describes the ice flow. Here, the surface-elevation grid is described in detail, as it has been generated specifically for such a study and represents a new standard in accuracy and resolution for calculating surface slopes. The digital-elevation model was generated on a 10 km grid size from over 20 000 000 height estimates obtained from eight 35 d repeat cycles of ERS-1 radar-altimeter data. For surface slopes less than 0.4°, the accuracy is better than 1.5 m. In areas of high surface slope (coastal and mountainous regions), the altimeter measurements have been supplemented with data taken from the Antarctic Digital Database. South of 81.5°, data from the SPRI folio map have been used. The ice-thickness grid was produced from a combination of a redigitization of the SPRI folio and the original radio-echo-sounding flight lines. For areas of grounded ice, the elevation of the bed was estimated from surface elevation and ice thickness. Significant differences (in excess of 25% of ice thickness) were obtained between an earlier digitization of the folio bed-elevation map and the data set derived here. Furthermore, a new value of 25.6 × 106 km3 was obtained for the total volume of the ice sheet and ice shelves, which is a reduction of 12% compared with the original estimate derived during the compilation of the SPRI folio. These differences will have an important influence on the results obtained by numerical ice-sheet models.

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An improved Antarctic dataset for high resolution numerical ice sheet models (ALBMAP v1)

Earth System Science Data Discussions ◽

10.5194/essdd-3-195-2010 ◽

2010 ◽

Vol 3 (1) ◽

pp. 195-230 ◽

Cited By ~ 13

Author(s):

A. M. Le Brocq ◽

A. J. Payne ◽

A. Vieli

Keyword(s):

High Resolution ◽

Ice Sheet ◽

Surface Air Temperature ◽

Ice Thickness ◽

Geothermal Heat ◽

Antarctic Ice Sheet ◽

Continental Scale ◽

Ice Surface ◽

The Antarctic ◽

Ice Sheet Modelling

Abstract. The dataset described in this paper (ALBMAP) has been created for the purposes of high-resolution numerical ice sheet modelling of the Antarctic Ice Sheet. It brings together data on the ice sheet configuration (e.g. ice surface and ice thickness) and boundary conditions, such as the surface air temperature, accumulation and geothermal heat flux. The ice thickness and basal topography is based on the BEDMAP dataset (Lythe et al., 2001), however, there are a number of inconsistencies within BEDMAP and, since its release, more data has become available. The dataset described here addresses these inconsistencies, including some novel interpolation schemes for sub ice-shelf cavities, and incorporates some major new datasets. The inclusion of new datasets is not exhaustive, this considerable task is left for the next release of BEDMAP, however, the data and procedure documented here provides another step forward and demonstrates the issues that need addressing in a continental scale dataset useful for high resolution ice sheet modelling. The dataset provides an initial condition that is as close as possible to present-day ice sheet configuration, aiding modelling of the response of the Antarctic Ice Sheet to various forcings, which are, at present, not fully understood.

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Developing an emulator to calculate present temperature field in the Antarctic Ice Sheet

10.5194/egusphere-egu21-6029 ◽

2021 ◽

Author(s):

Catherine Ritz ◽

Christophe Dumas ◽

Marion Leduc-Leballeur ◽

Giovanni Macelloni ◽

Ghislain Picard ◽

...

Keyword(s):

Temperature Field ◽

Ice Sheet ◽

Surface Velocity ◽

Computational Time ◽

Ice Thickness ◽

Ice Flow ◽

Antarctic Ice Sheet ◽

Computationally Expensive ◽

The Antarctic ◽

Geothermal Flux

Ice temperature within the ice is a crucial characteristic to understand the Antarctic ice sheet evolution because temperature is coupled to ice flow. Since temperature is only measured at few locations in deep boreholes, we only rely on numerical modelling to assess ice sheet-wide temperature. However, the design of such models leads to a number of challenges. One important difficulty is that the temperature field strongly depends on the geothermal flux which is still poorly known (see White paper by Burton-Johnson and others,2020 ). Another point is that up to now there is no fully suitable model, especially for inverse approaches: i) analytical solutions are only valid in slowly flowing regions; ii) models solving only the heat equation by prescribing geometry and ice flow do not take into account the past changes in ice thickness and ice flow and do not couple ice flow and temperature. Conversely, 3D thermomechanical models that simulate the evolution of the ice sheet take into account all the relevant processes but they are too computationally expensive to be used in inverse approaches. Moreover, they do not provide a perfect fit between observed and simulated geometry (ice thickness, surface elevation) for the present-day ice sheets and this affects the simulated temperature field.GRISLI (Quiquet et al. 2018), belongs to this family of thermomechanically coupled ice sheet models An emulator, based on deep neural network (DNN), has been developed in order to speed-up the simulation of present-day ice temperature. We use GRISLI outputs that come from 4 simulations, each covers 900000 years (8 glacial-interglacial cycles) to get rid of the initial configuration influence. The simulations differ by the geothermal flux map used as boundary condition. Finally a database is built where each ice column for each simulation is a sample used to train the DNN. For each sample, the input layer (precursor) is a vector of the present-day characteristics: ice thickness, surface temperature, geothermal flux, accumulation rate, surface velocity and surface slope. The predicted output (output layer) is the vertical profile of temperature. In the training, the weights of the network are optimized by comparison with the GRISLI temperature. The first results are very encouraging with a RMSE of ~ 0.6 &#176;C (calculated from the difference between the emulated temperatures and GRISLI temperatures over all the samples and all the depths). Once trained, the computational time of GRISLI-DNN for generating temperature field of whole Antarctica (16000 columns) is about 20 s.The first application (in the framework of the ESA project 4D-Antarctica, see Leduc-Leballeur presentation in this session) will be to use this emulator associated with SMOS satellite observations to infer the 3D temperature field and improve our knowledge of geothermal flux. Indeed, it has been shown that SMOS data, coupled with glaciological and electromagnetic models, give an indication of temperature in the upper 1000 m of the ice sheet. Our emulator could also be used for initialization of computationally expensive ice sheet models.

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