Applications of Satellite Altimetry to Study the Antarctic Ice Sheet

2017 ◽  
pp. 505-522 ◽  
Author(s):  
Frédérique Remy ◽  
Anthony Memin ◽  
Isabella Velicogna
Keyword(s):  
Satellite Altimetry ◽  
Ice Sheet ◽  
Antarctic Ice Sheet ◽  
The Antarctic

scholarly journals A new approach to estimate ice dynamic rates using satellite observations in East Antarctica

2016 ◽  
Author(s):  
Bianca Kallenberg ◽  
Paul Tregoning ◽  
Janosch F. Hoffmann ◽  
Rhys Hawkins ◽  
Anthony Purcell ◽  
...  
Keyword(s):  
Mass Balance ◽  
Satellite Altimetry ◽  
Ice Sheet ◽  
East Antarctica ◽  
Surface Mass Balance ◽  
Antarctic Ice Sheet ◽  
Surface Mass ◽  
Elevation Changes ◽  
Ice Sheet Mass Balance ◽  
The Antarctic

Abstract. Mass balance changes of the Antarctic ice sheet are of significant interest due to its sensitivity to climatic changes and its contribution to changes in global sea level. While regional climate models successfully estimate mass input due to snowfall, it remains difficult to estimate the amount of mass loss due to ice dynamic processes. It's often been assumed that changes in ice dynamic rates only need to be considered when assessing long term ice sheet mass balance; however, two decades of satellite altimetry observations reveal that the Antarctic ice sheet changes unexpectedly and much more dynamically than previously expected. Despite available estimates on ice dynamic rates obtained from radar altimetry, information about changes in ice dynamic rates are still limited, especially in East Antarctica. Without understanding ice dynamic rates it is not possible to properly assess changes in ice sheet mass balance, surface elevation or to develop ice sheet models. In this study we investigate the possibility of estimating ice dynamic rates by removing modelled rates of surface mass balance, firn compaction and bedrock uplift from satellite altimetry and gravity observations. With similar rates of ice discharge acquired from two different satellite missions we show that it is possible to obtain an approximation of ice dynamic rates by combining altimetry and gravity observations. Thus, surface elevation changes due to surface mass balance, firn compaction and ice dynamic rates can be modelled and correlate with observed elevation changes from satellite altimetry.

scholarly journals The influence of Antarctic ice loss on polar motion: an assessment based on GRACE and multi-mission satellite altimetry

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Franziska Göttl ◽  
Andreas Groh ◽  
Michael Schmidt ◽  
Ludwig Schröder ◽  
Florian Seitz
Keyword(s):  
Gravity Field ◽  
Polar Motion ◽  
Satellite Altimetry ◽  
Motion Vector ◽  
Ice Sheet ◽  
Position Vector ◽  
Random Errors ◽  
Excitation Functions ◽  
Antarctic Ice Sheet ◽  
The Antarctic

AbstractIncreasing ice loss of the Antarctic Ice Sheet (AIS) due to global climate change affects the orientation of the Earth’s spin axis with respect to an Earth-fixed reference system (polar motion). Here the contribution of the decreasing AIS to the excitation of polar motion is quantified from precise time variable gravity field observations of the Gravity Recovery and Climate Experiment (GRACE) and from measurements of the changing ice sheet elevation from altimeter satellites. While the GRACE gravity field models need to be reduced by noise and leakage effects from neighboring subsystems, the ice volume changes observed by satellite altimetry have to be converted into ice mass changes. In this study we investigate how much individual gravimetry and altimetry solutions differ from each other. We show that due to combination of individual solutions systematic and random errors of the data processing can be reduced and the robustness of the geodetic derived AIS polar motion excitations can be increased. We investigate the interannual variability of the Antarctic polar motion excitation functions by means of piecewise linear trends. We find that the long-term behavior of the three ice sheet subregions: EAIS (East Antarctic Ice Sheet), WAIS (West Antarctic Ice Sheet) and APIS (Antarctic Peninsula Ice Sheet) is quite different. While APIS polar motion excitations show no significant interannual variations during the study period $$2003-2015$$ 2003 - 2015 , the trend of the WAIS and EAIS polar motion excitations increased in 2006 and again in 2009 while it started slightly to decline in 2013. AIS mass changes explain about $$45\%$$ 45 % of the observed magnitude of the polar motion vector (excluding glacial isosatic adjustment). They cause the pole position vector to drift along $$59^{\circ }$$ 59 ∘ East longitude with an amplitude of 2.7 mas/yr. Thus the contribution of the AIS has to be considered to close the budget of the geophysical excitation functions of polar motion.

scholarly journals Identifying areas of low-profile ice sheet and outcrop damming in the Antarctic ice sheet by ERS-1 satellite altimetry

1998 ◽  
Vol 27 ◽  
pp. 1-6 ◽  
Author(s):  
David G. Vaughan ◽  
Jonathan L. Bamber
Keyword(s):  
Satellite Altimetry ◽  
Ice Sheet ◽  
Surface Elevation ◽  
Two Dimensional ◽  
Ice Flow ◽  
Antarctic Ice Sheet ◽  
Continental Scale ◽  
Low Profile ◽  
Elevation Model ◽  
The Antarctic

A digital elevation model (DEM) of the surface of the Antarctic ice sheet is compared with a simple two-dimensional ice-flow model to illuminate gross distortions (>500 m) of the ice-surface elevation. We use a DEM derived from ERS-1 satellite altimetry, airborne data and TWERLE balloon data. This is compared with an ice-sheet elevation model generated by applying theoretical surface elevations, calculated for two-dimensional ice flow, to isolines of distance from the grounding line (continentality). The model is scaled using only one parameter, to match the measured surface elevation at Dome Argus. The model is far from rigorous, violating continuity conditions, ignoring variations in surface mass balance and temperature, and assuming uniform basal conditions. However, the comparison of model and observed surface elevations is illuminating in terms of the behaviour of the ice sheet at a continental scale. Across the ice sheet the rms difference between modelled elevation and the DEM is around 300 m, but much of this results from isolated areas of much greater disagreement. We ascribe these gross differences to the effects of basal conditions. in four areas, the observed surface is more than 500 m higher than the modelled surface. Most of these are immediately upstream of substantial areas of rock outcrop and are caused by the damming effect of these mountain ranges. in nine areas, the measured surface is more than 500 m lower than predicted. Eight of these areas, in West Antarctica and the Lambert Glacier basin, are associated with suspected areas of basal sliding. The ninth is an area of 250 000 km2 in East Antarctica not previously noted as having unusual flow characteristics, but for which very few-data exist. We speculate that this area results from unusual basal conditions resulting in a low-profile ice sheet. A low-profile ice sheet of this size with in the East Antarctic ice sheet indicates that basal conditions are perhaps more variable than previously thought.

scholarly journals Four decades of surface elevation change of the Antarctic Ice Sheet from multi-mission satellite altimetry

2018 ◽  
Author(s):  
Ludwig Schröder ◽  
Martin Horwath ◽  
Reinhard Dietrich ◽  
Veit Helm
Keyword(s):  
Time Series ◽  
Satellite Altimetry ◽  
Ice Sheet ◽  
Surface Elevation ◽  
Elevation Change ◽  
Antarctic Ice Sheet ◽  
Mission Satellite ◽  
Surface Elevation Change ◽  
Precipitation Anomalies ◽  
The Antarctic

Abstract. We developed an approach for a multi-mission satellite altimetry analysis over the Antarctic Ice Sheet which comprises Seasat, Geosat, ERS-1, ERS-2, Envisat, ICESat and CryoSat-2. In a first step we apply a consistent reprocessing of the radar alitmetry data which improves the measurement precision by up to 50 %. We then perform a joint repeat altimetry analysis of all missions. We estimate inter-mission offsets by approaches adapted to the temporal overlap or non-overlap and to the similarity or dissimilarity of involved altimetry techniques. Hence, we obtain monthly grids forming a combined surface elevation change time series. Owing to the early missions Seasat and Geosat, the time series span almost four decades from 07/1978 to 12/2017 over 25 % of the ice sheet area (coastal regions of East Antarctica and the Antarctic Peninsula). Since the launch of ERS-1 79 % of the ice sheet area is covered by observations. Over this area, we obtain a negative volume trend of −34 ± 5 km3 yr−1 for the more than 25-year period (04/1992–12/2017). These volume losses have significantly accelerated to a rate of −170 ± 11 km3 yr−1 for 2010–2017. Interannual variations significantly impact decadal volume rates which highlights the importance of the long-term time series. Our time series show a high coincidence with modeled cumulated precipitation anomalies and with satellite gravimetry. This supports the interpretation with respect to snowfall anomalies or dynamic thinning. Moreover, the correlation with cumulated precipitation anomalies back to the Seasat and Geosat periods highlights that the inter-mission offsets were successfully corrected and that the early missions add valuable information.

scholarly journals Identifying areas of low-profile ice sheet and outcrop damming in the Antarctic ice sheet by ERS-1 satellite altimetry

1998 ◽  
Vol 27 ◽  
pp. 1-6 ◽  
Author(s):  
David G. Vaughan ◽  
Jonathan L. Bamber
Keyword(s):  
Satellite Altimetry ◽  
Ice Sheet ◽  
Surface Elevation ◽  
Two Dimensional ◽  
Ice Flow ◽  
Antarctic Ice Sheet ◽  
Continental Scale ◽  
Low Profile ◽  
Elevation Model ◽  
The Antarctic

A digital elevation model (DEM) of the surface of the Antarctic ice sheet is compared with a simple two-dimensional ice-flow model to illuminate gross distortions (>500 m) of the ice-surface elevation. We use a DEM derived from ERS-1 satellite altimetry, airborne data and TWERLE balloon data. This is compared with an ice-sheet elevation model generated by applying theoretical surface elevations, calculated for two-dimensional ice flow, to isolines of distance from the grounding line (continentality). The model is scaled using only one parameter, to match the measured surface elevation at Dome Argus. The model is far from rigorous, violating continuity conditions, ignoring variations in surface mass balance and temperature, and assuming uniform basal conditions. However, the comparison of model and observed surface elevations is illuminating in terms of the behaviour of the ice sheet at a continental scale. Across the ice sheet the rms difference between modelled elevation and the DEM is around 300 m, but much of this results from isolated areas of much greater disagreement. We ascribe these gross differences to the effects of basal conditions. in four areas, the observed surface is more than 500 m higher than the modelled surface. Most of these are immediately upstream of substantial areas of rock outcrop and are caused by the damming effect of these mountain ranges. in nine areas, the measured surface is more than 500 m lower than predicted. Eight of these areas, in West Antarctica and the Lambert Glacier basin, are associated with suspected areas of basal sliding. The ninth is an area of 250 000 km2 in East Antarctica not previously noted as having unusual flow characteristics, but for which very few-data exist. We speculate that this area results from unusual basal conditions resulting in a low-profile ice sheet. A low-profile ice sheet of this size with in the East Antarctic ice sheet indicates that basal conditions are perhaps more variable than previously thought.

scholarly journals Four decades of Antarctic surface elevation changes from multi-mission satellite altimetry

2019 ◽  
Vol 13 (2) ◽  
pp. 427-449 ◽  
Author(s):  
Ludwig Schröder ◽  
Martin Horwath ◽  
Reinhard Dietrich ◽  
Veit Helm ◽  
Michiel R. van den Broeke ◽  
...  
Keyword(s):  
Time Series ◽  
Satellite Altimetry ◽  
Average Rate ◽  
Ice Sheet ◽  
Surface Elevation ◽  
Antarctic Ice Sheet ◽  
Mission Satellite ◽  
Elevation Changes ◽  
Dronning Maud Land ◽  
The Antarctic

Abstract. We developed a multi-mission satellite altimetry analysis over the Antarctic Ice Sheet which comprises Seasat, Geosat, ERS-1, ERS-2, Envisat, ICESat and CryoSat-2. After a consistent reprocessing and a stepwise calibration of the inter-mission offsets, we obtained monthly grids of multi-mission surface elevation change (SEC) with respect to the reference epoch 09/2010 (in the format of month/year) from 1978 to 2017. A validation with independent elevation changes from in situ and airborne observations as well as a comparison with a firn model proves that the different missions and observation modes have been successfully combined to a seamless multi-mission time series. For coastal East Antarctica, even Seasat and Geosat provide reliable information and, hence, allow for the analysis of four decades of elevation changes. The spatial and temporal resolution of our result allows for the identification of when and where significant changes in elevation occurred. These time series add detailed information to the evolution of surface elevation in such key regions as Pine Island Glacier, Totten Glacier, Dronning Maud Land or Lake Vostok. After applying a density mask, we calculated time series of mass changes and found that the Antarctic Ice Sheet north of 81.5∘ S was losing mass at an average rate of -85±16 Gt yr−1 between 1992 and 2017, which accelerated to -137±25 Gt yr−1 after 2010.

scholarly journals A digital elevation model of the Antarctic ice sheet derived from ERS-1 altimeter data and comparison with terrestrial measurements

1994 ◽  
Vol 20 ◽  
pp. 48-54
Author(s):  
Jonathan L. Bamber
Keyword(s):  
Standard Deviation ◽  
Digital Elevation Model ◽  
Satellite Altimetry ◽  
Ice Sheet ◽  
Altimeter Data ◽  
Geopotential Model ◽  
Antarctic Ice Sheet ◽  
Digital Elevation ◽  
Elevation Model ◽  
The Antarctic

The launch of ERS-1 provides coverage, by satellite altimetry, of 80% of the Antarctic ice sheet, allowing topographic mapping of areas which previously had a dearth of accurate elevation data. Four 35 d repeat cycles of fastdelivery altimeter data were used in this study, comprising a total of approximately 1000000 height estimates. About 40% of these were rejected during a careful filtering procedure designed to remove erroneous values caused by poor tracking or complete loss of the returned echo. The OSU-91A geopotential model was used to convert ellipsoidal elevations to geoidal values. Corrections for surface slope were applied and a Digital Elevation Model (DEM) was produced with a grid spacing of 20km.The precision of the data was assessed from an analysis of crossing points of ascending and descending tracks. For 43864 cross-overs, the standard deviation was 6.8m. Regional biases associated with geoid, orbit and topography-induced errors reduce the accuracy of the height measurements. This was assessed by a comparison with ground-survey data. The DEM was compared with a 700km levelling survey, with an accuracy ranging from 1 to 5m, from the Lambert Glacier basin region (≈73° S, 55° E). The mean difference was found to be-1.6m with a standard deviation of 14m. A similar result was obtained for a 600km traverse line in Wilkes Land (75° S,≈1l0° E).The DEM was then compared with a digitized version of the Scott Polar Research Institute (SPRI) Antarctic folio map. This map was derived from orthometric measurements of surface elevation, primarily from pressure altimetry. Differences in excess of 300 m were observed between the two data sets. Only 37% of the region covered showed agreement to better than 50m, and a significant proportion ofthis was composed of the Ross and Filchner-Ronne Ice Shelves. The largest discrepancies occurred in marginal areas where there is poor coverage by both satellite altimetry and terrestrial data. Inland, significant differences were also found.

A new elevation change time series of the Antarctic Ice Sheet from Envisat and CryoSat-2 radar altimetry

2020 ◽  
Author(s):  
Baojun Zhang ◽  
Quanming Yang ◽  
Zemin Wang ◽  
Hong Geng ◽  
Jiachun An ◽  
...  
Keyword(s):  
Time Series ◽  
Satellite Altimetry ◽  
Ice Sheet ◽  
Least Square ◽  
Surface Elevation ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic ◽  
Elevation Changes ◽  
The Antarctic

<p>Satellite altimetry is an important data source for ice sheet change observation. The long-term time series of ice sheet changes can be obtained by combining satellite altimetry missions with similar sensor characteristics. Then, how to correct the inter-mission offsets becomes an important scientific issue. Review of previous studies, we found that the observations of satellite ascending and descending orbits also have an important influence on the estimation of inter-mission offsets. On this basis, have created a new least-square fitting mathematical model to estimate and correct the errors of ascending and descending orbits and inter-mission offsets by introducing the inter-mission offsets terms related to the observations of ascending and descending orbits. Utilizing this model, we developed a time series of monthly Antarctic ice sheet elevation changes of 5 km grid from May 2002 to April 2019. A validation with surface elevation from airborne observations and a comparison with surface elevation changes from ICESat proved that the proposed model can successfully estimate and correct the errors and be used to construct multi-mission surface elevation time series. Without a doubt, the temporal and spatial changes of Antarctic ice sheet elevation can be obtained from our monthly grid time series. From the time series, we find that over the period May 2002 to April 2019 the loss of ice and snow in the Antarctic ice sheet mainly occurred in the glaciers along the Amundsen coast in the West Antarctic and the Totten glacier in the East Antarctic, while the accumulation took place in Queen Maud of the East Antarctic. In May 2002, the Antarctic ice sheet experienced a volume loss of -71.4 ± 11.7 km<sup>3</sup>/yr, with an acceleration of –5.8 ± 1.2 km<sup>3</sup>/yr<sup>2</sup> over the period May 2002 to April 2019, including 45.0 ± 9.6 km<sup>3</sup>/yr and 0.1 ±1.0 km<sup>3</sup>/yr<sup>2</sup> for the East Antarctic ice sheet, -97.0 ± 4.4 km<sup>3</sup>/yr and -7.6 ±0.5 km<sup>3</sup>/yr<sup>2</sup> for the West Antarctic ice sheet and -19.5 ± 5.3 km<sup>3</sup>/yr and 1.7 ±0.5 km<sup>3</sup>/yr<sup>2</sup> for the Antarctic Peninsula ice sheet.</p>

scholarly journals A digital elevation model of the Antarctic ice sheet derived from ERS-1 altimeter data and comparison with terrestrial measurements

1994 ◽  
Vol 20 ◽  
pp. 48-54 ◽  
Author(s):  
Jonathan L. Bamber
Keyword(s):  
Standard Deviation ◽  
Digital Elevation Model ◽  
Satellite Altimetry ◽  
Ice Sheet ◽  
Altimeter Data ◽  
Geopotential Model ◽  
Antarctic Ice Sheet ◽  
Digital Elevation ◽  
Elevation Model ◽  
The Antarctic

The launch of ERS-1 provides coverage, by satellite altimetry, of 80% of the Antarctic ice sheet, allowing topographic mapping of areas which previously had a dearth of accurate elevation data. Four 35 d repeat cycles of fastdelivery altimeter data were used in this study, comprising a total of approximately 1000000 height estimates. About 40% of these were rejected during a careful filtering procedure designed to remove erroneous values caused by poor tracking or complete loss of the returned echo. The OSU-91A geopotential model was used to convert ellipsoidal elevations to geoidal values. Corrections for surface slope were applied and a Digital Elevation Model (DEM) was produced with a grid spacing of 20km.The precision of the data was assessed from an analysis of crossing points of ascending and descending tracks. For 43864 cross-overs, the standard deviation was 6.8m. Regional biases associated with geoid, orbit and topography-induced errors reduce the accuracy of the height measurements. This was assessed by a comparison with ground-survey data. The DEM was compared with a 700km levelling survey, with an accuracy ranging from 1 to 5m, from the Lambert Glacier basin region (≈73° S, 55° E). The mean difference was found to be-1.6m with a standard deviation of 14m. A similar result was obtained for a 600km traverse line in Wilkes Land (75° S,≈1l0° E).The DEM was then compared with a digitized version of the Scott Polar Research Institute (SPRI) Antarctic folio map. This map was derived from orthometric measurements of surface elevation, primarily from pressure altimetry. Differences in excess of 300 m were observed between the two data sets. Only 37% of the region covered showed agreement to better than 50m, and a significant proportion ofthis was composed of the Ross and Filchner-Ronne Ice Shelves. The largest discrepancies occurred in marginal areas where there is poor coverage by both satellite altimetry and terrestrial data. Inland, significant differences were also found.

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