Separating Geophysical Signals Using GRACE and High‐Resolution Data: A Case Study in Antarctica

Engels, Olga; Gunter, B. C.; Riva, Riccardo; Klees, R.

doi:10.1029/2018gl079670

Cited by 11 publications

(24 citation statements)

References 36 publications

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“…Previous studies combining gravimetry and altimetry are based on linear seasonal deterministic models over certain periods (Riva et al, 2009;Gunter et al, 2014;Martín-Español et al, 2016a;Sasgen et al, 2017;Engels et al, 2018). However, signals in the firn and ice layer over the Antarctic Ice Sheet (AIS) show inter-annual changes (Horwath et al, 2012;Ligtenberg et al, 2012;Mémin et al, 2015).…”

Section: Time-series-based Combinationmentioning

confidence: 99%

“…An ice mass trend estimation can be determined using time-variable gravity fields from the Gravity Recovery And Climate Experiment (GRACE) mission (e.g. Groh et al, 2014;Forsberg et al, 2017), which is continued by its follow-on mission GRACE-FO.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, a joint inversion has been presented that takes into account the rheological parameters of the solid Earth (Sasgen et al, 2017). Engels et al (2018) use a regularized parameter estimation approach (dynamic patch) to resolve the superimposed mass trends in Antarctica. Martín-Español et al (2016b) compared available GIA solutions from forward modelling and inverse estimation and have shown that differences are larger than indicated uncertainties.…”

Section: Introductionmentioning

confidence: 99%

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Sensitivity of inverse glacial isostatic adjustment estimates over Antarctica

et al. 2020

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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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Section: Time-series-based Combinationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sensitivity of inverse glacial isostatic adjustment estimates over Antarctica

et al. 2020

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“…Extending the temporal and spatial coverage of measurements that reflect the contemporary pattern of solid Earth deformation across the WS sector would provide invaluable insight into recent ice sheet change and the stability of the current ice sheet configuration. Spatially continuous estimates of isostatic rebound are beginning to be derived via data inversion, whereby satellite gravimetry and altimetry data are combined to simultaneously invert for contemporary ice mass loss and the GIA signal, often also incorporating GPS observations (Engels et al, ; Gunter et al, ; Martín‐Español et al, ; Sasgen et al, ). Uncertainties are large, due to assumptions related to the interpretation of satellite data, but at least they can be formally quantified in this independent, data‐driven approach.…”

Section: Solid Earth Measurements and Modellingmentioning

confidence: 99%

Major Ice Sheet Change in the Weddell Sea Sector of West Antarctica Over the Last 5,000 Years

Siegert

Kingslake

Ross

et al. 2019

Reviews of Geophysics

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Until recently, little was known about the Weddell Sea sector of the West Antarctic Ice Sheet. In the last 10 years, a variety of expeditions and numerical modelling experiments have improved knowledge of its glaciology, glacial geology and tectonic setting. Two of the sector's largest ice streams rest on a steep reverse‐sloping bed yet, despite being vulnerable to change, satellite observations show contemporary stability. There is clear evidence for major ice sheet reconfiguration in the last few thousand years, however. Knowing precisely how and when the ice sheet has changed in the past would allow us to better understand whether it is now at risk. Two competing hypotheses have been established for this glacial history. In one, the ice sheet retreated and thinned progressively from its Last Glacial Maximum position. Retreat stopped at, or very near, the present position in the Late Holocene. Alternatively, in the Late Holocene, the ice sheet retreated significantly upstream of its present grounding line and then advanced to today's location due to glacial isostatic adjustment and ice shelf and ice rise buttressing. Both hypotheses point to data and theory in their support yet neither has been unequivocally tested or falsified. Here we review geophysical evidence to determine how each hypothesis has been formed, where there are inconsistencies in the respective glacial histories, how they may be tested or reconciled, and what new evidence is required to reach a common model for the Late Holocene ice sheet history of the Weddell Sea sector of West Antarctica.

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“…Previous studies combining gravimetry and altimetry are based on linear-seasonal deterministic models over certain periods (Riva et al, 2009;Gunter et al, 2014;Martín-Español et al, 2016a;Sasgen et al, 2017;Engels et al, 2018). However, signals (Horwath et al, 2012;Ligtenberg et al, 2012;Mémin et al, 2015).…”

Section: Combination Of Time Seriesmentioning

confidence: 99%

Sensitivity of inverse glacial isostatic adjustment estimates over Antarctica

Willen¹,

Horwath²,

Schröder³

et al. 2019

Preprint

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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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Separating Geophysical Signals Using GRACE and High‐Resolution Data: A Case Study in Antarctica

Cited by 11 publications

References 36 publications

Sensitivity of inverse glacial isostatic adjustment estimates over Antarctica

Sensitivity of inverse glacial isostatic adjustment estimates over Antarctica

Major Ice Sheet Change in the Weddell Sea Sector of West Antarctica Over the Last 5,000 Years

Sensitivity of inverse glacial isostatic adjustment estimates over Antarctica

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