Empirical estimation of present-day Antarctic glacial isostatic adjustment and ice mass change

Abstract. This study explores an approach that simultaneously estimates Antarctic mass balance and glacial isostatic adjustment (GIA) through the combination of satellite gravity and altimetry data sets. The results improve upon previous efforts by incorporating a firn densification model to account for firn compaction and surface processes as well as reprocessed data sets over a slightly longer period of time. A range of different Gravity Recovery and Climate Experiment (GRACE) gravity models were evaluated and a new Ice, Cloud, and Land Elevation Satellite (ICESat) surface height trend map computed using an overlapping footprint approach. When the GIA models created from the combination approach were compared to in situ GPS ground station displacements, the vertical rates estimated showed consistently better agreement than recent conventional GIA models. The new empirically derived GIA rates suggest the presence of strong uplift in the Amundsen Sea sector in West Antarctica (WA) and the Philippi/Denman sectors, as well as subsidence in large parts of East Antarctica (EA). The total GIA-related mass change estimates for the entire Antarctic ice sheet ranged from 53 to 103 Gt yr−1, depending on the GRACE solution used, with an estimated uncertainty of ±40 Gt yr−1. Over the time frame February 2003–October 2009, the corresponding ice mass change showed an average value of −100 ± 44 Gt yr−1 (EA: 5 ± 38, WA: −105 ± 22), consistent with other recent estimates in the literature, with regional mass loss mostly concentrated in WA. The refined approach presented in this study shows the contribution that such data combinations can make towards improving estimates of present-day GIA and ice mass change, particularly with respect to determining more reliable uncertainties.

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Empirical estimation of present-day Antarctic glacial isostatic adjustment and ice mass change

The Cryosphere Discussions ◽

10.5194/tcd-7-3497-2013 ◽

2013 ◽

Vol 7 (4) ◽

pp. 3497-3541 ◽

Cited By ~ 5

Author(s):

B. C. Gunter ◽

O. Didova ◽

R. E. M. Riva ◽

S. R. M. Ligtenberg ◽

J. T. M. Lenaerts ◽

...

Keyword(s):

Time Frame ◽

Gravity Models ◽

Mass Change ◽

Data Sets ◽

Glacial Isostatic Adjustment ◽

Empirical Estimation ◽

Satellite Gravity ◽

Amundsen Sea ◽

Average Value ◽

Isostatic Adjustment

Abstract. This study explores an approach that simultaneously estimates Antarctic mass balance and glacial isostatic adjustment (GIA) through the combination of satellite gravity and altimetry data sets. The results improve upon previous efforts by incorporating reprocessed data sets over a longer period of time, and now include a firn densification model to account for firn compaction and surface processes. A range of different GRACE gravity models were evaluated, as well as a new ICESat surface height trend map computed using an overlapping footprint approach. When the GIA models created from the combination approach were compared to in-situ GPS ground station displacements, the vertical rates estimated showed consistently better agreement than existing GIA models. In addition, the new empirically derived GIA rates suggest the presence of strong uplift in the Amundsen Sea and Philippi/Denman sectors, as well as subsidence in large parts of East Antarctica. The total GIA mass change estimates for the entire Antarctic ice sheet ranged from 53 to 100 Gt yr−1, depending on the GRACE solution used, and with an estimated uncertainty of ±40 Gt yr−1. Over the time frame February 2003–October 2009, the corresponding ice mass change showed an average value of −100 ± 44 Gt yr−1 (EA: 5 ± 38, WA: −105 ± 22), consistent with other recent estimates in the literature, with the mass loss mostly concentrated in West Antarctica. The refined approach presented in this study shows the contribution that such data combinations can make towards improving estimates of present day GIA and ice mass change, particularly with respect to determining more reliable uncertainties.

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Sensitivity of inverse glacial isostatic adjustment estimates over Antarctica

The Cryosphere ◽

10.5194/tc-14-349-2020 ◽

2020 ◽

Vol 14 (1) ◽

pp. 349-366

Author(s):

Matthias O. Willen ◽

Martin Horwath ◽

Ludwig Schröder ◽

Andreas Groh ◽

Stefan R. M. Ligtenberg ◽

...

Keyword(s):

Mass Balance ◽

Bias Correction ◽

Total Mass ◽

Process Models ◽

Mass Change ◽

Quality Data ◽

Data Sets ◽

Glacial Isostatic Adjustment ◽

Satellite Gravimetry ◽

Isostatic Adjustment

Abstract. Glacial isostatic adjustment (GIA) is a major source of uncertainty for ice and ocean mass balance estimates derived from satellite gravimetry. In Antarctica the gravimetric effect of cryospheric mass change and GIA are of the same order of magnitude. Inverse estimates from geodetic observations hold some promise for mass signal separation. Here, we investigate the combination of satellite gravimetry and altimetry and demonstrate that the choice of input data sets and processing methods will influence the resultant GIA inverse estimate. This includes the combination that spans the full GRACE record (April 2002–August 2016). Additionally, we show the variations that arise from combining the actual time series of the differing data sets. Using the inferred trends, we assess the spread of GIA solutions owing to (1) the choice of different degree-1 and C20 products, (2) viable candidate surface-elevation-change products derived from different altimetry missions corresponding to different time intervals, and (3) the uncertainties associated with firn process models. Decomposing the total-mass signal into the ice mass and the GIA components is strongly dependent on properly correcting for an apparent bias in regions of small signal. Here our ab initio solutions force the mean GIA and GRACE trend over the low precipitation zone of East Antarctica to be zero. Without applying this bias correction, the overall spread of total-mass change and GIA-related mass change using differing degree-1 and C20 products is 68 and 72 Gt a−1, respectively, for the same time period (March 2003–October 2009). The bias correction method collapses this spread to 6 and 5 Gt a−1, respectively. We characterize the firn process model uncertainty empirically by analysing differences between two alternative surface mass balance products. The differences propagate to a 10 Gt a−1 spread in debiased GIA-related mass change estimates. The choice of the altimetry product poses the largest uncertainty on debiased mass change estimates. The spread of debiased GIA-related mass change amounts to 15 Gt a−1 for the period from March 2003 to October 2009. We found a spread of 49 Gt a−1 comparing results for the periods April 2002–August 2016 and July 2010–August 2016. Our findings point out limitations associated with data quality, data processing, and correction for apparent biases.

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Sensitivity of inverse glacial isostatic adjustment estimates over Antarctica

10.5194/tc-2019-95 ◽

2019 ◽

Author(s):

Matthias O. Willen ◽

Martin Horwath ◽

Ludwig Schröder ◽

Andreas Groh ◽

Stefan R. M. Ligtenberg ◽

...

Keyword(s):

Mass Balance ◽

Bias Correction ◽

Total Mass ◽

Mass Change ◽

Data Sets ◽

Glacial Isostatic Adjustment ◽

Satellite Gravimetry ◽

Isostatic Adjustment ◽

Time Period ◽

Combining Data

Abstract. Glacial isostatic adjustment (GIA) is a major source of uncertainty in estimated ice and ocean mass balance that are based on satellite gravimetry. In particular over Antarctica the gravimetric effect of cryospheric mass change and GIA are of the same order of magnitude. Inverse estimates from geodetic observations are promising for separating the two superimposed mass signals. Here, we investigate the combination of satellite gravimetry and altimetry and how the choice of input data sets and processing details affect the inverse GIA estimates. This includes the combination for almost full GRACE lifespan (2002-04/2016-08). Further we show results from combining data sets on time-series level. Specifically on trend level, we assess the spread of GIA solutions that arises from (1) the choice of different degree-1 and C20 products, (2) different surface elevation change products derived from different altimetry missions and associated to different time intervals, and (3) the uncertainty of firn-process models. The decomposition of the total-mass signal into the ice-mass signal and the apparent GIA-mass signal depends strongly on correcting for apparent biases in initial solutions by forcing the mean GIA and GRACE trend over the low precipitation zone of East Antarctica to be zero. Prior to bias correction, the overall spread of total-mass change and apparent GIA-mass change using differing degree-1 and C20 products is 68 and 72 Gt a−1, respectively, for the same time period (2003-03/2009-10). The bias correction suppresses this spread to 6 and 5 Gt a−1, respectively. We characterise the firn-process model uncertainty empirically by analysing differences between two alternative surface-mass-balance products. The differences propagate to a 21 Gt a−1 spread in apparent GIA-mass-change estimates. The choice of the altimetry product poses the largest uncertainty on debiased mass-change estimates. The overall spread of debiased GIA-mass change amounts to 18 and 49 Gt a−1 for a fixed time period (2003-03/2009-10) and various time periods, respectively. Our findings point out limitations associated with data processing, correction for apparent biases, and time dependency.

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Geodetic observations for constraining mantle processes in Antarctica

Geological Society London Memoirs ◽

10.1144/m56-2021-22 ◽

2021 ◽

pp. M56-2021-22

Author(s):

Mirko Scheinert ◽

Olga Engels ◽

Ernst J. O. Schrama ◽

Wouter van der Wal ◽

Martin Horwath

Keyword(s):

Data Sets ◽

Satellite Mission ◽

Amundsen Sea ◽

Isostatic Adjustment ◽

Geodynamic Processes ◽

Grace Satellite ◽

Mantle Processes ◽

Gnss Measurements ◽

The Individual ◽

Seismic Deformation

AbstractGeodynamic processes in Antarctica such as glacial isostatic adjustment (GIA) and post-seismic deformation are measured by geodetic observations such as GNSS and satellite gravimetry. GNSS measurements have been comprising continuous measurements as well as episodic measurements since the mid-1990s. The estimated velocities typically reach an accuracy of 1 mm/a for horizontal and 2 mm/a for vertical velocities. However, the elastic deformation due to present-day ice-load change needs to be considered accordingly.Space gravimetry derives mass changes from small variations in the inter-satellite distance of a pair of satellites, starting with the GRACE satellite mission in 2002 and continuing with the GRACE-FO mission launched in 2018. The spatial resolution of the measurements is low (about 300 km) but the measurement error is homogeneous across Antarctica. The estimated trends contain signals from ice mass change, local and global GIA signal. To combine the strengths of the individual data sets statistical combinations of GNSS, GRACE and satellite altimetry data have been developed. These combinations rely on realistic error estimates and assumptions of snow density. Nevertheless, they capture signal that is missing from geodynamic forward models such as the large uplift in the Amundsen Sea sector due to low-viscous response to century-scale ice-mass changes.

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Estimation of present-day glacial isostatic adjustment, ice mass change and elastic vertical crustal deformation over the Antarctic ice sheet

Journal of Glaciology ◽

10.1017/jog.2017.37 ◽

2017 ◽

Vol 63 (240) ◽

pp. 703-715 ◽

Cited By ~ 5

Author(s):

BAOJUN ZHANG ◽

ZEMIN WANG ◽

FEI LI ◽

JIACHUN AN ◽

YUANDE YANG ◽

...

Keyword(s):

Antarctic Peninsula ◽

Crustal Deformation ◽

Ice Sheet ◽

East Antarctica ◽

Mass Change ◽

Glacial Isostatic Adjustment ◽

Antarctic Ice Sheet ◽

Isostatic Adjustment ◽

The Antarctic ◽

Vertical Crustal Deformation

ABSTRACTThis study explores an iterative method for simultaneously estimating the present-day glacial isostatic adjustment (GIA), ice mass change and elastic vertical crustal deformation of the Antarctic ice sheet (AIS) for the period October 2003–October 2009. The estimations are derived by combining mass measurements of the GRACE mission and surface height observations of the ICESat mission under the constraint of GPS vertical crustal deformation rates in the spatial domain. The influence of active subglacial lakes on GIA estimates are mitigated for the first time through additional processing of ICESat data. The inferred GIA shows that the strongest uplift is found in the Amundsen Sea Embayment (ASE) sector and subsidence mostly occurs in Adelie Terre and the East Antarctica inland. The total GIA-related mass change estimates for the entire AIS, West Antarctica Ice Sheet (WAIS), East Antarctica Ice Sheet (EAIS), and Antarctic Peninsula Ice Sheet (APIS) are 43 ± 38, 53 ± 24, −23 ± 29 and 13 ± 6 Gt a−1, respectively. The overall ice mass change of the AIS is −46 ± 43 Gt a−1 (WAIS: −104 ± 25, EAIS: 77 ± 35, APIS: −20 ± 6). The most significant ice mass loss and most significant elastic vertical crustal deformations are concentrated in the ASE and northern Antarctic Peninsula.

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On Moho Determination by the Vening Meinesz-Moritz Technique

10.5772/intechopen.97449 ◽

2021 ◽

Author(s):

Lars Erik Sjöberg ◽

Majid Abrehdary

Keyword(s):

Least Squares ◽

Moho Depth ◽

Glacial Isostatic Adjustment ◽

Altimetry Data ◽

Satellite Gravity ◽

Isostatic Adjustment ◽

Uncertainty Estimates ◽

Least Squares Adjustment ◽

Moho Depths ◽

Vening Meinesz

This chapter describes a theory and application of satellite gravity and altimetry data for determining Moho constituents (i.e. Moho depth and density contrast) with support from a seismic Moho model in a least-squares adjustment. It presents and applies the Vening Meinesz-Moritz gravimetric-isostatic model in recovering the global Moho features. Internal and external uncertainty estimates are also determined. Special emphasis is devoted to presenting methods for eliminating the so-called non-isostatic effects, i.e. the gravimetric signals from the Earth both below the crust and from partly unknown density variations in the crust and effects due to delayed Glacial Isostatic Adjustment as well as for capturing Moho features not related with isostatic balance. The global means of the computed Moho depths and density contrasts are 23.8±0.05 km and 340.5 ± 0.37 kg/m3, respectively. The two Moho features vary between 7.6 and 70.3 km as well as between 21.0 and 650.0 kg/m3. Validation checks were performed for our modeled crustal depths using a recently published seismic model, yielding an RMS difference of 4 km.

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Estimation of Glacial Isostatic Adjustment uplift rate in the Totten glacier's outlet from GPS and GRACE

10.5194/gstm2020-40 ◽

2020 ◽

Author(s):

Mahdiyeh Razeghi ◽

Shin-Chan Han ◽

Matt King ◽

Paul Tregoning

Keyword(s):

Time Series ◽

High Resolution ◽

Elastic Deformation ◽

East Antarctica ◽

Mass Change ◽

Glacial Isostatic Adjustment ◽

Change Model ◽

Isostatic Adjustment ◽

Elastic Rebound ◽

Casey Station

<p>Glacial Isostatic Adjustment (GIA) refers to the gradual response of the solid Earth to the deglaciation of historic ice sheets. &#160;This ongoing rebound is contributing to the measurements of gravity change and land deformation, respectively, by Gravity Recovery And Climate Experiment (GRACE) and Global Positioning System (GPS). &#160;When these space geodetic data are used to quantify the present-day ice mass change, the effect such as GIA must be accounted for. &#160;In this study, we developed a method to estimate GIA and elastic deformation by the present-day ice mass change in the GPS time series with the example of Casey station in East Antarctica. &#160;We determined a high-resolution, present-day ice mass change model on the outlet of Totten Glacier and calculated the elastic rebound over the area. &#160;Our high-resolution model indicated a total mass loss of 15.7 &#177; 0.5 Gt/yr on the outlet of Totten Glacier from 2002 to 2017 with the accelerated loss in the last half of the period. &#160;We estimated the viscoelastic deformation attributed to GIA by removing the predicted elastic deformation from GPS measurements. &#160;Four different GPS position solutions for the Casey station, the continuously operating GPS station near the area, were examined. &#160;The estimated GIA signal appears to be within 0.3 &#8211; 1.3 mm/yr which shows its contribution on the vertical deformation between 30 &#8211; 60 % among different GPS solutions. &#160;On the other hand, the vertical elastic deformation trend is predicted to be 0.7 mm/yr from the ice mass change model.&#160; The GPS measured seasonal variation is explained equally by atmospheric-oceanic loading and degree-1 loading with a couple mm amplitude in vertical time series.&#160; The elastic rebound from the present-day ice mass change also perturbed the horizontal displacement by 0.13 mm/yr in west and 0.21 mm/yr in north directions. &#160;This is in the opposite to the plate motion of the East Antarctica around the Casey station and amounts approximately up to 10 % of the measured tectonic motion.</p>

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Altimetry, gravimetry, GPS and viscoelastic modelling data for the joint inversion for glacial isostatic adjustment in Antarctica (ESA STSE Project REGINA)

10.5194/essd-2017-46 ◽

2017 ◽

Author(s):

Ingo Sasgen ◽

Alba Martín-Español ◽

Alexander Horvath ◽

Volker Klemann ◽

Elizabeth J. Petrie ◽

...

Keyword(s):

Solid Earth ◽

Joint Inversion ◽

Ice Sheet ◽

Data Sets ◽

Glacial Isostatic Adjustment ◽

Response Functions ◽

Forward Modelling ◽

Satellite Gravimetry ◽

Isostatic Adjustment ◽

The Antarctic

Abstract. A major uncertainty in determining the mass balance of the Antarctic ice sheet from measurements of satellite gravimetry, and to a lesser extent satellite altimetry, is the poorly known correction for the ongoing deformation of the solid Earth caused by glacial isostatic adjustment (GIA). In the past decade, much progress has been made in consistently modelling the ice sheet and solid Earth interactions; however, forward-modelling solutions of GIA in Antarctica remain uncertain due to the sparsity of constraints on the ice sheet evolution, as well as the Earth's rheological properties. An alternative approach towards estimating GIA is the joint inversion of multiple satellite data – namely, satellite gravimetry, satellite altimetry and GPS, which reflect, with different sensitivities, trends of recent glacial changes and GIA. Crucial to the success of this approach is the accuracy of the space-geodetic data sets. Here, we present reprocessed rates of surface-ice elevation change (Envisat/ICESat; 2003–2009), gravity field change (GRACE; 2003–2009) and bedrock uplift (GPS; 1995–2013.7). The data analysis is complemented by the forward-modelling of viscoelastic response functions to disc load forcing, allowing us to relate GIA-induced surface displacements with gravity changes for different rheological parameters of the solid Earth. The data and modelling results presented here are available in the Pangea archive; https://doi.pangaea.de/10.1594/PANGAEA.875745. The data sets are the input streams for the joint inversion estimate of present-day ice-mass change and GIA, focusing on Antarctica. However, the methods, code and data provided in this paper are applicable to solve other problems, such as volume balances of the Antarctic ice sheet, or to other geographical regions, in the case of the viscoelastic response functions. This paper presents the first of two contributions summarizing the work carried out within a European Space Agency funded study, REGINA.

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Antarctic ice-mass balance 2003 to 2012: regional reanalysis of GRACE satellite gravimetry measurements with improved estimate of glacial-isostatic adjustment based on GPS uplift rates

The Cryosphere ◽

10.5194/tc-7-1499-2013 ◽

2013 ◽

Vol 7 (5) ◽

pp. 1499-1512 ◽

Cited By ~ 61

Author(s):

I. Sasgen ◽

H. Konrad ◽

E. R. Ivins ◽

M. R. Van den Broeke ◽

J. L. Bamber ◽

...

Keyword(s):

Mass Balance ◽

Regional Scale ◽

Mass Movement ◽

Glacial Isostatic Adjustment ◽

Glacial Cycle ◽

Amundsen Sea ◽

Satellite Gravimetry ◽

Isostatic Adjustment ◽

Uplift Rates ◽

Grace Satellite Gravimetry

Abstract. We present regional-scale mass balances for 25 drainage basins of the Antarctic Ice Sheet (AIS) from satellite observations of the Gravity and Climate Experiment (GRACE) for time period January 2003 to September 2012. Satellite gravimetry estimates of the AIS mass balance are strongly influenced by mass movement in the Earth interior caused by ice advance and retreat during the last glacial cycle. Here, we develop an improved glacial-isostatic adjustment (GIA) estimate for Antarctica using newly available GPS uplift rates, allowing us to more accurately separate GIA-induced trends in the GRACE gravity fields from those caused by current imbalances of the AIS. Our revised GIA estimate is considerably lower than previous predictions, yielding an estimate of apparent mass change of 53 ± 18 Gt yr−1. Therefore, our AIS mass balance of −114 ± 23 Gt yr−1 is less negative than previous GRACE estimates. The northern Antarctic Peninsula and the Amundsen Sea sector exhibit the largest mass loss (−26 ± 3 Gt yr−1 and −127 ± 7 Gt yr−1, respectively). In contrast, East Antarctica exhibits a slightly positive mass balance (26 ± 13 Gt yr−1), which is, however, mostly the consequence of compensating mass anomalies in Dronning Maud and Enderby Land (positive) and Wilkes and George V Land (negative) due to interannual accumulation variations. In total, 6% of the area constitutes about half the AIS imbalance, contributing 151 ± 7 Gt yr−1 (ca. 0.4 mm yr−1) to global mean sea-level change. Most of this imbalance is caused by ice-dynamic speed-up expected to prevail in the near future.

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Altimetry, gravimetry, GPS and viscoelastic modeling data for the joint inversion for glacial isostatic adjustment in Antarctica (ESA STSE Project REGINA)

Earth System Science Data ◽

10.5194/essd-10-493-2018 ◽

2018 ◽

Vol 10 (1) ◽

pp. 493-523 ◽

Cited By ~ 6

Author(s):

Ingo Sasgen ◽

Alba Martín-Español ◽

Alexander Horvath ◽

Volker Klemann ◽

Elizabeth J. Petrie ◽

...

Keyword(s):

Solid Earth ◽

Joint Inversion ◽

Ice Sheet ◽

Forward Modeling ◽

Data Sets ◽

Glacial Isostatic Adjustment ◽

Response Functions ◽

Satellite Gravimetry ◽

Isostatic Adjustment ◽

The Antarctic

Abstract. The poorly known correction for the ongoing deformation of the solid Earth caused by glacial isostatic adjustment (GIA) is a major uncertainty in determining the mass balance of the Antarctic ice sheet from measurements of satellite gravimetry and to a lesser extent satellite altimetry. In the past decade, much progress has been made in consistently modeling ice sheet and solid Earth interactions; however, forward-modeling solutions of GIA in Antarctica remain uncertain due to the sparsity of constraints on the ice sheet evolution, as well as the Earth's rheological properties. An alternative approach towards estimating GIA is the joint inversion of multiple satellite data – namely, satellite gravimetry, satellite altimetry and GPS, which reflect, with different sensitivities, trends in recent glacial changes and GIA. Crucial to the success of this approach is the accuracy of the space-geodetic data sets. Here, we present reprocessed rates of surface-ice elevation change (Envisat/Ice, Cloud,and land Elevation Satellite, ICESat; 2003–2009), gravity field change (Gravity Recovery and Climate Experiment, GRACE; 2003–2009) and bedrock uplift (GPS; 1995–2013). The data analysis is complemented by the forward modeling of viscoelastic response functions to disc load forcing, allowing us to relate GIA-induced surface displacements with gravity changes for different rheological parameters of the solid Earth. The data and modeling results presented here are available in the PANGAEA database (https://doi.org/10.1594/PANGAEA.875745). The data sets are the input streams for the joint inversion estimate of present-day ice-mass change and GIA, focusing on Antarctica. However, the methods, code and data provided in this paper can be used to solve other problems, such as volume balances of the Antarctic ice sheet, or can be applied to other geographical regions in the case of the viscoelastic response functions. This paper presents the first of two contributions summarizing the work carried out within a European Space Agency funded study: Regional glacial isostatic adjustment and CryoSat elevation rate corrections in Antarctica (REGINA).

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