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

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.  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).  When these space geodetic data are used to quantify the present-day ice mass change, the effect such as GIA must be accounted for.  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.  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.  Our high-resolution model indicated a total mass loss of 15.7 ± 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.  We estimated the viscoelastic deformation attributed to GIA by removing the predicted elastic deformation from GPS measurements.  Four different GPS position solutions for the Casey station, the continuously operating GPS station near the area, were examined.  The estimated GIA signal appears to be within 0.3 – 1.3 mm/yr which shows its contribution on the vertical deformation between 30 – 60 % among different GPS solutions.  On the other hand, the vertical elastic deformation trend is predicted to be 0.7 mm/yr from the ice mass change model.  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.  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.  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>

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

2017 ◽  
Vol 63 (240) ◽  
pp. 703-715 ◽  
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.

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

2013 ◽  
Vol 7 (4) ◽  
pp. 3497-3541 ◽  
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.

scholarly journals Sensitivity of inverse glacial isostatic adjustment estimates over Antarctica

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.

scholarly journals Sensitivity of inverse glacial isostatic adjustment estimates over Antarctica

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.

scholarly journals Post-LGM coastline evolution of the NW Sicilian Channel: Comparing high-resolution geophysical data with Glacial Isostatic Adjustment modeling

PLoS ONE ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. e0228087 ◽  
Author(s):  
Emanuele Lodolo ◽  
Gaia Galassi ◽  
Giorgio Spada ◽  
Massimo Zecchin ◽  
Dario Civile ◽  
...  
Keyword(s):  
High Resolution ◽  
Geophysical Data ◽  
Glacial Isostatic Adjustment ◽  
Isostatic Adjustment ◽  
Coastline Evolution

scholarly journals The Rapid and Steady Mass Loss of the Patagonian Icefields throughout the GRACE Era: 2002–2017

2019 ◽  
Vol 11 (8) ◽  
pp. 909 ◽  
Author(s):  
Andreas Richter ◽  
Andreas Groh ◽  
Martin Horwath ◽  
Erik Ivins ◽  
Eric Marderwald ◽  
...  
Keyword(s):  
Time Series ◽  
Mass Loss ◽  
A Priori ◽  
Global Navigation Satellite Systems ◽  
Mass Change ◽  
Satellite Systems ◽  
Isostatic Adjustment ◽  
Global Navigation Satellite ◽  
Gravity Recovery ◽  
The Antarctic

We use the complete gravity recovery and climate experiment (GRACE) Level-2 monthly time series to derive the ice mass changes of the Patagonian Icefields (Southern Andes). The glacial isostatic adjustment is accounted for by a regional model that is constrained by global navigation satellite systems (GNSS) uplift observations. Further corrections are applied concerning the effect of mass variations in the ocean, in the continental water storage, and of the Antarctic ice sheet. The 161 monthly GRACE gravity field solutions are inverted in the spatial domain through the adjustment of scaling factors applied to a-priori ice mass change patterns based on published remote sensing results for the Southern and Northern Patagonian Icefields, respectively. We infer an ice mass change rate of −24.4 ± 4.7 Gt/a for the Patagonian Icefields between April 2002 and June 2017, which corresponds to a contribution to the eustatic sea level rise of 0.067 ± 0.013 mm/a. Our time series of monthly ice mass changes reveals no indication for an acceleration in ice mass loss. We find indications that the Northern Patagonian Icefield contributes more to the integral ice loss than previously assumed.

scholarly journals Separation of tectonic and local components of horizontal GPS station velocities: a case study for glacial isostatic adjustment in East Antarctica

2020 ◽  
Vol 222 (3) ◽  
pp. 1555-1569
Author(s):  
Ross J Turner ◽  
Anya M Reading ◽  
Matt A King
Keyword(s):  
Synthetic Data ◽  
Real Data ◽  
East Antarctica ◽  
Signal Separation ◽  
Spatial Density ◽  
Glacial Isostatic Adjustment ◽  
Local Component ◽  
Isostatic Adjustment ◽  
Plate Rotation ◽  
Gps Station

SUMMARY Accurate measurement of the local component of geodetic motion at GPS stations presents a challenge due to the need to separate this signal from the tectonic plate rotation. A pressing example is the observation of glacial isostatic adjustment (GIA) which constrains the Earth’s response to ice unloading, and hence, contributions of ice-covered regions such as Antarctica to global sea level rise following ice mass loss. While both vertical and horizontal motions are of interest in general, we focus on horizontal GPS velocities which typically contain a large component of plate rotation and a smaller local component primarily relating to GIA. Incomplete separation of these components introduces significant bias into estimates of GIA motion vectors. We present the results of a series of tests based on the motions of GPS stations from East Antarctica: (1) signal separation for sets of synthetic data that replicate the geometric character of non-separable, and separable, GIA-like horizontal velocities; and (2) signal separation for real GPS station data with an appraisal of uncertainties. For both synthetic and real motions, we compare results where the stations are unweighted, and where each station is areal-weighted using a metric representing the inverse of the spatial density of neighbouring stations. From the synthetic tests, we show that a GIA-like signal is recoverable from the plate rotation signal providing it has geometric variability across East Antarctica. We also show that areal-weighting has a very significant effect on the ability to recover a GIA-like signal with geometric variability, and hence on separating the plate rotation and local components. For the real data, assuming a rigid Antarctic plate, fitted plate rotation parameters compare well with other studies in the literature. We find that 25 out of 36 GPS stations examined in East Antarctica have non-zero local horizontal velocities, at the 2σ level, after signal separation. We make the code for weighted signal separation available to assist in the consistent appraisal of separated signals, and the comparison of likely uncertainty bounds, for future studies.

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

2014 ◽  
Vol 8 (2) ◽  
pp. 743-760 ◽  
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 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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