Antarctic ice-mass balance 2002 to 2011: regional re-analysis of GRACE satellite gravimetry measurements with improved estimate of glacial-isostatic adjustment

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 the years 2002–2011. 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 (upper) estimate of apparent mass change of 48 ± 18 Gt yr−1. Therefore, our AIS mass balance of −103 ± 23 Gt yr−1 is considerably less negative than previous GRACE estimates. The Northern Antarctic Peninsula and the Amundsen Sea Sector exhibit the largest mass loss (−25 ± 6 Gt yr−1 and −126 ± 11 Gt yr−1, respectively). In contrast, East Antarctica exhibits a slightly positive mass balance (19 ± 16 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, 7% of the area constitute more than half of the AIS imbalance (53%), contributing −151 ± 9 Gt yr−1 to global mean sea-level change. Most of this imbalance is caused by long-term ice-dynamic speed up expected to prevail in the future.

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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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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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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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The Prominent Role of GRACE in the Series of IMBIE Studies: Future Plans and Prominent Issues

10.5194/gstm2020-63 ◽

2020 ◽

Author(s):

Erik Ivins ◽

Andrew Shepherd

Keyword(s):

Mass Balance ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Glacial Isostatic Adjustment ◽

Isostatic Adjustment ◽

General Plan ◽

Ice Mass Balance ◽

Grace Mission ◽

Phase I And Ii

The Ice Mass Balance Intercomparison Exercize &#160;(IMBIE) was initiated in 2011 with the intent of better reconciling the various reports&#160; on the Greenland ice sheet (GrIS) &#160;and Antarctic ice sheet (AIS) mass balance during the 2000&#8217;s. The focused study was funded and promoted by both ESA and NASA to better understand the origins of &#160;contradictory results using space observations for a 20 year-long period: 1990-2010. Here we review some of the main results of phase I and II of IMBIE and the strength of the GRACE mission results. &#160;For 20-year long trends (2002-2021) trends are influenced by glacial isostatic adjustment (GIA) in Greenland, but with more profound consequence for Antarctica. IMBIE-I determined a mass balance trend for 1992-2011: -142 &#177; 49 and -71 &#177; 83 Gt/yr, for GrIS and AIS, respectively. &#160;IMBIE-II was open to a wider sampling of international &#160;investigative teams and the results for GrIS over 1992-2018 changed to -150 &#177; 13 Gt/yr. Most notably the 1-sigma formal errors reported in IMBIE-II were 25% of those reported in the earlier IMBIE-I study for GrIS. For Antarctica the most notable contrast in results was the total value of the trend over 1992-2017 (IMBIE-II) in contrast 1992-2011 (IMBIE-I) (-109 &#177; 56 vs -71 &#177; 83 Gt/yr, respectively). The loss estimate for AIS rose by 67% and the error also reduced by about 33%. Glacial isostatic adjustment (GIA) estimates for Antarctica cluster around + 54 Gt/yr (meaning their correction adds to the negativity of the mass balance result for GRACE and GRACE-FO). &#160;The East Antarctica Ice Sheet (EAIS) has trend errors for the estimate 1992-2017 (IMBIE-II) that continue to dwarf the uncertainty: +5 &#177; 46 Gt/yr. Beneath EAIS, GIA is also most uncertain and models have the greatest spread. We discuss the general plan for IMBIE-III that is currently forming.

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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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Coupled solid Earth – Antarctic ice sheet simulations with VILMA and PISM

10.5194/egusphere-egu21-8050 ◽

2021 ◽

Author(s):

Torsten Albrecht ◽

Meike Bagge ◽

Ricarda Winkelmann ◽

Volker Klemann

Keyword(s):

Solid Earth ◽

Sea Level ◽

Climate Modeling ◽

Three Dimensional ◽

Ice Sheet ◽

Glacial Cycle ◽

Glacial Cycles ◽

Amundsen Sea ◽

Antarctic Ice Sheet ◽

Isostatic Adjustment

The Antarctic Ice Sheet rests on a bed that is characterized by tectonical activity and hence by a heterogeneous rheology. Spots of extremely weak lithosphere structure could have strong impacts on the Glacial Isostatic Adjustment and hence on the stability of the ice sheet, possibly also for confined glacier regions and on timescales of decades down to even years (Barletta et al., 2018). We coupled the VIscoelastic Lithosphere and MAntle model (VILMA) to the Parallel Ice Sheet Model (PISM) and ran simulations over the last two glacial cycles. In this framework, VILMA considers both viscoelastic deformations of the solid Earth and gravitationally consistent mass redistribution in the ocean by solving for the sea-level equation (Martinec et al., 2018). In turn, PISM interprets this as a vertical shift in bed topography that directly affects the stress balance within the ice sheet and hence the grounding line dynamics at the interface of ice, ocean and bedrock. Here we present first results of the coupled Antarctic glacial-cycle simulations and investigate technical aspects, such as optimal coupling time steps, iteration schemes and convergence, for both one-dimensional and three-dimensional Earth structures. This project is part of the German Climate Modeling Initiative, PalMod2.&#160;References:Barletta et al., 2018. Observed rapid bedrock uplift in Amundsen Sea Embayment promotes ice-sheet stability. Science,&#160;360, pp.1335-1339. DOI: 10.1126/science.aao1447Martinec et al., 2018. A benchmark study of numerical implementations of the sea level equation in GIA modelling. Geophysical Journal International,&#160;215(1), pp.389-414. DOI: 10.1093/gji/ggy280&#160;

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Validation of GIA models in north-east Greenland using densified GNSS measurements and refined estimates of present-day ice-mass changes

10.5194/egusphere-egu21-8019 ◽

2021 ◽

Author(s):

Maria Theresia Kappelsberger ◽

Undine Strößenreuther ◽

Mirko Scheinert ◽

Martin Horwath ◽

Andreas Groh ◽

...

Keyword(s):

Greenland Ice Sheet ◽

Repeated Measurements ◽

East Greenland ◽

Satellite Gravimetry ◽

Isostatic Adjustment ◽

North East ◽

Elastic Load ◽

Uplift Rates ◽

Grace Satellite Gravimetry ◽

Gnss Measurements

Models of glacial-isostatic adjustment (GIA) exhibit large differences in north-east Greenland, reflecting uncertainties about glacial history and solid Earth rheology. The GIA uncertainties feed back to uncertainties in present-day mass-balance estimates from satellite gravimetry. We present results from repeated and continuous GNSS measurements which provide direct observables of the bedrock displacement. The repeated measurements were conducted within five measurement campaigns between 2008 and 2017. They reveal uplift rates in north-east Greenland in the range of 2.8 to 8.9 mm yr-1. We used the observed uplift rates to validate different GIA models in conjunction with estimates of the elastic load deformation induced by present-day ice-mass changes and ocean mass redistribution. To determine present-day ice-mass changes for both the Greenland Ice Sheet and the peripheral glaciers, we combined CryoSat-2 satellite altimetry data with GRACE satellite gravimetry data. The different GIA models were consistently used in all processing steps. Our comparison between observed and predicted uplift rates clearly favours GIA models that show low rates (0.7 to 4.4 mm yr-1 at the GNSS sites) over GIA models with higher rates of up to 8.3 mm yr-1. Applying the correction predicted by the GIA model favoured in north-east Greenland we estimate an ice-mass loss of 233 &#177; 43 Gt yr-1 for entire Greenland (including peripheral glaciers) over the period July 2010 to June 2017.

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Contribution of GRACE Satellite Gravimetry in Global and Regional Hydrology, and in Ice Sheets Mass Balance

Water Resources Management and Modeling ◽

10.5772/34212 ◽

2012 ◽

Cited By ~ 2

Author(s):

Frappart Frdric ◽

Ramillien Guillaume

Keyword(s):

Mass Balance ◽

Ice Sheets ◽

Satellite Gravimetry ◽

Regional Hydrology ◽

Grace Satellite Gravimetry ◽

Grace Satellite

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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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