Antarctic glacial isostatic adjustment: a new assessment

2005 ◽  
Vol 17 (4) ◽  
pp. 541-553 ◽  
Author(s):  
ERIK R. IVINS ◽  
THOMAS S. JAMES
Keyword(s):  
Mass Balance ◽  
Antarctic Peninsula ◽  
Ross Sea ◽  
Ice Sheet ◽  
Gravity Change ◽  
Glacial Isostatic Adjustment ◽  
Crustal Motion ◽  
Isostatic Adjustment ◽  
Time Space ◽  
The Antarctic

The prediction of crustal motions and gravity change driven by glacial isostatic adjustment (GIA) in Antarctica is critically dependent on the reconstruction of the configuration and thickness of the ice sheet during the Late Pleistocene and Holocene. The collection and analysis of field data to improve the reconstruction has occurred at an accelerated pace during the past decade. At the same time, space-based imaging and altimetry, combined with on-ice velocity measurements using Global Positioning System (GPS) geodesy, has provided better assessments of the present-day mass balance of the Antarctic ice sheet. Present-day mass change appears to be dominated by deglaciation that is, in large part, a continuation of late-Holocene evolution. Here a new ice load model is constructed, based on a synthesis of the current constraints on past ice history and present-day mass balance. The load is used to predict GIA crustal motion and geoid change. Compared to existing glacioisostatic models, the new ice history model is significantly improved in four aspects: (i) the timing of volume losses in the region ranging from the Ross Sea sector to the Antarctic Peninsula, (ii) the maximum ice heights in parts of the Ellsworth and Transantarctic Mountains, (iii) maximum grounding line position in Pine Island Bay, the Antarctic Peninsula, and in the Ross Sea, (iv) incorporation of present-day net mass balance estimates. The predicted present-day GIA uplift rates peak at 14–18 mm yr−1 and geoid rates peak at 4–5 mm yr−1 for two contrasting viscosity models. If the asthenosphere underlying West Antarctica has a low viscosity then the predictions could change substantially due to the extreme sensitivity to recent (past two millennia) ice mass variability. Future observations of crustal motion and gravity change will substantially improve the understanding of sub-Antarctic lithospheric and mantle rheology.

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.

Automated mapping of Antarctic supraglacial lakes and streams using machine learning

2020 ◽  
Author(s):  
Mariel Dirscherl ◽  
Andreas Dietz ◽  
Celia Baumhoer ◽  
Christof Kneisel ◽  
Claudia Kuenzer
Keyword(s):  
Machine Learning ◽  
Mass Balance ◽  
Antarctic Peninsula ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Antarctic Ice Sheet ◽  
Supraglacial Lakes ◽  
The Antarctic ◽  
Sentinel 2

<p>Antarctica stores ~91 % of the global ice mass making it the biggest potential contributor to global sea-level-rise. With increased surface air temperatures during austral summer as well as in consequence of global climate change, the ice sheet is subject to surface melting resulting in the formation of supraglacial lakes in local surface depressions. Supraglacial meltwater features may impact Antarctic ice dynamics and mass balance through three main processes. First of all, it may cause enhanced ice thinning thus a potentially negative Antarctic Surface Mass Balance (SMB). Second, the temporary injection of meltwater to the glacier bed may cause transient ice speed accelerations and increased ice discharge. The last mechanism involves a process called hydrofracturing i.e. meltwater-induced ice shelf collapse caused by the downward propagation of surface meltwater into crevasses or fractures, as observed along large coastal sections of the northern Antarctic Peninsula. Despite the known impact of supraglacial meltwater features on ice dynamics and mass balance, the Antarctic surface hydrological network remains largely understudied with an automated method for supraglacial lake and stream detection still missing. Spaceborne remote sensing and data of the Sentinel missions in particular provide an excellent basis for the monitoring of the Antarctic surface hydrological network at unprecedented spatial and temporal coverage.</p><p>In this study, we employ state-of-the-art machine learning for automated supraglacial lake and stream mapping on basis of optical Sentinel-2 satellite data. With more detail, we use a total of 72 Sentinel-2 acquisitions distributed across the Antarctic Ice Sheet together with topographic information to train and test the selected machine learning algorithm. In general, our machine learning workflow is designed to discriminate between surface water, ice/snow, rock and shadow being further supported by several automated post-processing steps. In order to ensure the algorithm’s transferability in space and time, the acquisitions used for training the machine learning model are chosen to cover the full circle of the 2019 melt season and the data selected for testing the algorithm span the 2017 and 2018 melt seasons. Supraglacial lake predictions are presented for several regions of interest on the East and West Antarctic Ice Sheet as well as along the Antarctic Peninsula and are validated against randomly sampled points in the underlying Sentinel-2 RGB images. To highlight the performance of our model, we specifically focus on the example of the Amery Ice Shelf in East Antarctica, where we applied our algorithm on Sentinel-2 data in order to present the temporal evolution of maximum lake extent during three consecutive melt seasons (2017, 2018 and 2019).</p>

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

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

<p>The Ice Mass Balance Intercomparison Exercize  (IMBIE) was initiated in 2011 with the intent of better reconciling the various reports  on the Greenland ice sheet (GrIS)  and Antarctic ice sheet (AIS) mass balance during the 2000’s. The focused study was funded and promoted by both ESA and NASA to better understand the origins of  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.  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 ± 49 and -71 ± 83 Gt/yr, for GrIS and AIS, respectively.  IMBIE-II was open to a wider sampling of international  investigative teams and the results for GrIS over 1992-2018 changed to -150 ± 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 ± 56 vs -71 ± 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).  The East Antarctica Ice Sheet (EAIS) has trend errors for the estimate 1992-2017 (IMBIE-II) that continue to dwarf the uncertainty: +5 ± 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.</p>

Upper mantle viscosity structure and lithospheric thickness of Antarctica inferred from recent seismic models

2020 ◽  
Author(s):  
Douglas Wiens ◽  
Andrew Lloyd ◽  
Weisen Shen ◽  
Andrew Nyblade ◽  
Richard Aster ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Upper Mantle ◽  
Ice Sheet ◽  
West Antarctica ◽  
Lithospheric Thickness ◽  
Isostatic Adjustment ◽  
Low Viscosity ◽  
Mantle Viscosity ◽  
Seismic Models ◽  
The Antarctic

<p>Upper mantle viscosity structure and lithospheric thickness control the solid Earth response to variations in ice sheet loading. These parameters vary significantly across Antarctica, leading to strong regional differences in the timescale of glacial isostatic adjustment (GIA), with important implications for ice sheet models.  We estimate upper mantle viscosity structure and lithospheric thickness using two new seismic models for Antarctica, which take advantage of temporary broadband seismic stations deployed across Antarctica over the past 18 years. Shen et al. [2018] use receiver functions and Rayleigh wave velocities from earthquakes and ambient noise to develop a higher resolution model for the upper 200 km beneath Central and West Antarctica, where most of the seismic stations have been deployed. Lloyd et al [2019] use full waveform adjoint tomography to invert three-component earthquake seismograms for a radially anisotropic model covering Antarctica and adjacent oceanic regions to 800 km depth. We estimate the mantle viscosity structure from seismic structure using laboratory-derived relationships between seismic velocity, temperature, and rheology. Choice of parameters for this mapping is guided in part by recent regional estimates of mantle viscosity from geodetic measurements. We also describe and compare several different methods of estimating lithospheric thickness from seismic constraints.</p><p>The mantle viscosity estimates indicate regional variations of several orders of magnitude, with extremely low viscosity (< 10<sup>19</sup> Pa s) beneath the Amundsen Sea Embayment (ASE) and the Antarctic Peninsula, consistent with estimates from GIA models constrained by GPS data.  Lithospheric thickness is also highly variable, ranging from around 60 km in parts of West Antarctica to greater than 200 km beneath central East Antarctica. In East Antarctica, several prominent regions such as Dronning Maude Land and the Lambert Graben show much thinner lithosphere, consistent with Phanerozoic tectonic activity and lithospheric disruption. Thin lithosphere and low viscosity between the ASE and the Antarctic Peninsula likely result from the thermal effects of the slab window as the Phoenix-Antarctic plate boundary migrated northward during the Cenozoic. Low viscosity regions beneath the ASE and Marie Byrd Land coast connect to an offshore anomaly at depths of ~ 250 km, suggesting larger-scale thermal and geodynamic processes that may be linked to the initial Cretaceous rifting of New Zealand and Antarctica. Low mantle viscosity results in a characteristic GIA time scale on the order of several hundred years, such that isostatic adjustment occurs on the same time scale as grounding line retreat.  Thus the associated rebound may lessen the effect of the marine ice sheet instability proposed for the ASE region. </p>

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

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.

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

2018 ◽  
Vol 10 (1) ◽  
pp. 493-523 ◽  
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).

scholarly journals Increased ice loading in the Antarctic Peninsula since the 1850s and its effect on glacial isostatic adjustment

2012 ◽  
Vol 39 (17) ◽  
pp. n/a-n/a ◽  
Author(s):  
Grace A. Nield ◽  
Pippa L. Whitehouse ◽  
Matt A. King ◽  
Peter J. Clarke ◽  
Michael J. Bentley
Keyword(s):  
Antarctic Peninsula ◽  
Glacial Isostatic Adjustment ◽  
Isostatic Adjustment ◽  
The Antarctic

scholarly journals Mass evolution of the Antarctic Peninsula over the last two decades from a joint Bayesian inversion

2021 ◽  
Author(s):  
Stephen J. Chuter ◽  
Andrew Zammit-Mangion ◽  
Jonathan Rougier ◽  
Geoffrey Dawson ◽  
Jonathan L Bamber
Keyword(s):  
Mass Balance ◽  
Antarctic Peninsula ◽  
Joint Inversion ◽  
Ice Sheet ◽  
Surface Processes ◽  
Ice Dynamics ◽  
Bayesian Hierarchical ◽  
Relative Contribution ◽  
Mass Losses ◽  
The Antarctic

Abstract. The Antarctic Peninsula has been an increasingly significant contributor to Antarctic Ice Sheet mass losses over the last two decades. However, due to the challenges presented by the topography and geometry of the region, there remain large variations in mass balance estimates from conventional approaches and in assessing the relative contribution of individual ice sheet processes. Here, we use a regionally optimised Bayesian Hierarchical Model joint inversion approach, that combines data from multiple altimetry studies (ENVISAT, ICESat-1, CryoSat-2 swath), gravimetry (GRACE and GRACE-FO) and localised DEM differencing observations, to solve for annual mass trends and their attribution to individual driving processes for the period 2003–2019. The region experienced a mass imbalance rate of −19 ± 1.1 Gt yr−1 between 2003 and 2019, predominantly driven by accelerations in ice dynamic mass losses in the first decade and sustained thereafter. Inter-annual variability is driven by surface processes, particularly in 2016 due to increased precipitation driven by an extreme El Niño, which temporarily returned the sector back to a state of positive mass balance. In the West Palmer Land and the English Coast regions, surface processes are a greater contributor to mass loss than ice dynamics in the early part of the 2010s, although both processes are acting simultaneously. Our results show good agreement with conventional and other combination approaches, improving confidence in the robustness of mass trend estimates, and in turn, understanding of the region’s response to changes in external forcing.

Antarctic Peninsula mass trends from 2003 - 2016 using a Bayesian hierarchical model approach

2020 ◽  
Author(s):  
Stephen Chuter ◽  
Jonathan Rougier ◽  
Geoffrey Dawson ◽  
Jonathan Bamber
Keyword(s):  
Mass Balance ◽  
Spatial Resolution ◽  
Antarctic Peninsula ◽  
Ice Sheet ◽  
Stereo Image ◽  
Ice Dynamics ◽  
Antarctic Ice Sheet ◽  
Basin Scale ◽  
Grounding Line ◽  
The Antarctic

<p>Long-term continuous monitoring of Antarctic Ice Sheet mass balance is imperative to better understand its multi-decadal response to changes in climate and ocean forcing. Additionally, more accurate knowledge of contemporaneous mass balance is key for improved parameterisations in ice sheet models. The Antarctic Peninsula has undergone rapid changes in mass balance and ice dynamics over the last two decades, with satellite observations showing the presence of grounding line retreat and increases in ice sheet velocity. This is particularly the case after the collapse of the Larsen A and B ice shelves in 1995 and 2002, and more recently the glaciers draining the southern Antarctic Peninsula. As a result, this region provides analogues for future ice sheet response to ice shelf collapse in other regions of Antarctica. </p><p>Despite the region’s importance to understanding ice sheet dynamics, it is challenging to accurately assess mass balance due its geometry and mountainous topography. Conventional pulse-limited altimetry suffers from poor coverage and data loss over steep mountainous terrain, particularly before the launch of CryoSat-2 in 2010. In the case of gravimetry, the geometry of the region means the coarse spatial resolution of the GRACE mission (~300 km) cannot resolve small spatial scale glacier changes (particularly over northern Antarctic Peninsula) and suffers from signal leakage into the ocean. For the mass budget approach, the challenge of accurately modelling surface mass balance over the region’s mountainous topography coupled with the sparsity of ice thickness observations at the grounding line for many sectors can result in large uncertainties. As a result, it can be difficult to reconcile the results from different conventional approaches in this region. </p><p>To resolve this, we have developed and optimised the BHM framework used previously over the Antarctic Ice Sheet to specifically investigate the Antarctic Peninsula. This enables each latent process driving ice sheet mass change to be resolved at a higher spatial resolution compared to previous implementations across Antarctica as a whole. The new regional solution also incorporates more recent and higher resolution observations including: CryoSat-2 swath altimetry, stereo-image DEM differencing and NASA Operation Ice Bridge laser altimetry elevation rates. This is the first time such a range of observations of varying spatio-temporal resolutions will be combined into one assessment for the region. We will present results from the regionally optimised model from 2003 until present, including basin-scale mass trends and changes in spatial latent processes at an annual resolution. Additionally, we will discuss future opportunities, such as extending the record from this approach into the next decade and further understanding of the GIA response in this region. </p>

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