scholarly journals Radar Satellite Altimetry in Geodesy - Theory, Applications and Recent Developments

2021 ◽  
Author(s):  
Marijan Grgić ◽  
Tomislav Bašić
Keyword(s):  
Sea Level ◽  
Satellite Altimetry ◽  
Water Cycle ◽  
Ice Sheet ◽  
Radar Altimetry ◽  
Impact Monitoring ◽  
Recent Developments ◽  
Satellite Radar ◽  
Water Mass Balance ◽  
Radar Satellite

Radar satellite altimetry has revolutionized our understanding of the Earth’s sea-level shape and its change over time, monitoring of the natural and human-induced water cycle, marine gravity computations, seafloor relief (bathymetry) reconstruction, tectonics, water mass balance change monitoring, etc., thus providing significant impact in geodesy. Today satellite radar altimetry is critical for unifying the vertical height systems, regional and global geoid modeling, monitoring of the sea level rise impact, monitoring of the ice sheet melting, and others. This chapter gives an overview of the technology itself and the recent developments including the SAR (Synthetic Aperture Radar) altimetry, coastal altimetry retracking methods, and new satellite missions (e.g. Sentinel-6). Besides, the chapter presents recent applied studies utilizing the altimeter data for ice sheet monitoring, vertical land motion estimating, bathymetric computations, and marine geoid modeling.

scholarly journals Time-evolving mass loss of the Greenland ice sheet from satellite altimetry

2014 ◽  
Vol 8 (1) ◽  
pp. 1057-1093
Author(s):  
R. T. W. L. Hurkmans ◽  
J. L. Bamber ◽  
C. H. Davis ◽  
I. R. Joughin ◽  
K. S. Khvorostovsky ◽  
...  
Keyword(s):  
Mass Loss ◽  
Satellite Altimetry ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Laser Altimetry ◽  
Radar Altimetry ◽  
Appropriate Treatment ◽  
Satellite Radar

Abstract. Mass changes of the Greenland ice sheet may be estimated by the Input Output Method (IOM), satellite gravimetry, or via surface elevation change rates (dH / dt). Whereas the first two have been shown to agree well in reconstructing mass changes over the last decade, there are few decadal estimates from satellite altimetry and none that provide a time evolving trend that can be readily compared with the other methods. Here, we interpolate radar and laser altimetry data between 1995 and 2009 in both space and time to reconstruct the evolving volume changes. A firn densification model forced by the output of a regional climate model is used to convert volume to mass. We consider and investigate the potential sources of error in our reconstruction of mass trends, including geophysical biases in the altimetry, and the resulting mass change rates are compared to other published estimates. We find that mass changes are dominated by SMB until about 2001, when mass loss rapidly accelerates. The onset of this acceleration is somewhat later, and less gradual, compared to the IOM. Our time averaged mass changes agree well with recently published estimates based on gravimetry, IOM, laser altimetry, and with radar altimetry when merged with airborne data over outlet glaciers. We demonstrate, that with appropriate treatment, satellite radar altimetry can provide reliable estimates of mass trends for the Greenland ice sheet. With the inclusion of data from CryoSat II, this provides the possibility of producing a continuous time series of regional mass trends from 1992 onward.

scholarly journals Time-evolving mass loss of the Greenland Ice Sheet from satellite altimetry

2014 ◽  
Vol 8 (5) ◽  
pp. 1725-1740 ◽  
Author(s):  
R. T. W. L. Hurkmans ◽  
J. L. Bamber ◽  
C. H. Davis ◽  
I. R. Joughin ◽  
K. S. Khvorostovsky ◽  
...  
Keyword(s):  
Mass Loss ◽  
Satellite Altimetry ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Laser Altimetry ◽  
Radar Altimetry ◽  
Surface Mass ◽  
Satellite Radar

Abstract. Mass changes of the Greenland Ice Sheet may be estimated by the input–output method (IOM), satellite gravimetry, or via surface elevation change rates (dH/dt). Whereas the first two have been shown to agree well in reconstructing ice-sheet wide mass changes over the last decade, there are few decadal estimates from satellite altimetry and none that provide a time-evolving trend that can be readily compared with the other methods. Here, we interpolate radar and laser altimetry data between 1995 and 2009 in both space and time to reconstruct the evolving volume changes. A firn densification model forced by the output of a regional climate model is used to convert volume to mass. We consider and investigate the potential sources of error in our reconstruction of mass trends, including geophysical biases in the altimetry, and the resulting mass change rates are compared to other published estimates. We find that mass changes are dominated by surface mass balance (SMB) until about 2001, when mass loss rapidly accelerates. The onset of this acceleration is somewhat later, and less gradual, compared to the IOM. Our time-averaged mass changes agree well with recently published estimates based on gravimetry, IOM, laser altimetry, and with radar altimetry when merged with airborne data over outlet glaciers. We demonstrate that, with appropriate treatment, satellite radar altimetry can provide reliable estimates of mass trends for the Greenland Ice Sheet. With the inclusion of data from CryoSat-2, this provides the possibility of producing a continuous time series of regional mass trends from 1992 onward.

scholarly journals Ice-Sheet Topography From Geosat Radar Altimetry (Abstract)

1988 ◽  
Vol 11 ◽  
pp. 213 ◽  
Author(s):  
H. Jay Zwally ◽  
R. A. Bindschadler
Keyword(s):  
Standard Deviation ◽  
Ice Sheet ◽  
Satellite Orbit ◽  
Mean Value ◽  
Surface Elevation ◽  
Data Set ◽  
Radar Altimetry ◽  
Fitting Procedure ◽  
Optimal Spacing ◽  
Satellite Radar

Ice-sheet surface topography is the principal ice parameter obtainable from satellite radar altimetry. Surface-elevation maps of the East Antarctic ice sheet north of 72°S from Seasat data, collected between July and October 1978, and preliminary maps from Geosat data, collected between March 1985 and September 1986, are described. The Geosat data, obtained from the U.S. Navy as an unclassified data set, have greatly increased the density of elevation measurements. A principal correction to the altimeter measurements is obtained by applying a computer curve-fitting procedure to each radar waveform to correct for errors in the automatic range-tracking circuitry of the altimeter. The errors are caused by slow response to range variations due to undulations of the ice surface between successive measurements made at intervals of 662 m along track. The retracking correction for Geosat data has a standard deviation of 2.4 m and a mean value of 1.1m, values which are about 20% smaller than the corresponding values for Seasat. The positive mean correction indicates a common tendency of the altimeters' automatic tracking to give an excessive range to the surface. The precision of the measurements, given by the standard deviation of the range differences at cross-over points, is about 1.6 m before adjustment for errors in the radial position of the satellite orbit. The preliminary surface-elevation maps from Geosat data are improved over those produced from Seasat, mainly due to optimal spacing of successive ground tracks. The locations of ice divides and drainage basins along the East Antarctic coast are delineated by several methods, including vector plots of surface slope.

scholarly journals Monitoring Sea Level and Topography of Coastal Lagoons Using Satellite Radar Altimetry: The Example of the Arcachon Bay in the Bay of Biscay

2018 ◽  
Vol 10 (2) ◽  
pp. 297 ◽  
Author(s):  
Edward Salameh ◽  
Frédéric Frappart ◽  
Vincent Marieu ◽  
Alexandra Spodar ◽  
Jean-Paul Parisot ◽  
...  
Keyword(s):  
Sea Level ◽  
Coastal Lagoons ◽  
Bay Of Biscay ◽  
Radar Altimetry ◽  
Arcachon Bay ◽  
Satellite Radar ◽  
Satellite Radar Altimetry

Sea level in Thule measured with tide gauge, GNSS-IR and Satellite Altimetry

2020 ◽  
Author(s):  
Trine S. Dahl-Jensen ◽  
Shfaqat Abbas Khan ◽  
Simon D.P. Williams ◽  
Ole B. Andersen ◽  
Carsten A. Ludwigsen
Keyword(s):  
Sea Level ◽  
Satellite Altimetry ◽  
Tide Gauge ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Sea Level Changes ◽  
Level Measurement ◽  
Time Period ◽  
The Right ◽  
Gps Station

<p>Recent studies show that under the right conditions relative sea level can be measured using GNSS interferometric reflectometry (GNSS-IR). We test the possibility of using an existing GNET GPS station in Thule, Greenland, to measure inter annual changes in sea level by comparing sea level measurements from GNSS-IR with tide gauge observations and satellite altimetry data. GNET is a network of 56 permanent GPS stations positioned on the bedrock around the edge fo the Greenland ice sheet with the main purpose of monitoring ice mass changes. Currently, Thule is the only location in Greenland where we have both a tide gauge and a GPS station that is suitable for sea level measurement covering the same time period for more than a couple of years. If successful a number of other GPS stations are also expected to be suitable for GNSS-IR measurements of sea level. However, they lack the tide gauge station for testing.<br>We compare the measured sea level with uplift measured using the GPS and modeled from height changes of the Greenland ice sheet as well as sea surface temperatures and modeled sea level changes from gravimetry, in order to investigate the origin of sea level changes in the region.  <br> </p>

Bias in Estimates of Global Mean Sea Level Change Inferred from Satellite Altimetry

2018 ◽  
Vol 31 (13) ◽  
pp. 5263-5271 ◽  
Author(s):  
Megan Jeramaz Lickley ◽  
Carling C. Hay ◽  
Mark E. Tamisiea ◽  
Jerry X. Mitrovica
Keyword(s):  
Sea Level ◽  
Mass Flux ◽  
Satellite Altimetry ◽  
Ice Sheet ◽  
Sea Level Change ◽  
Global Ocean ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
Level Change ◽  
The Antarctic

Estimates of regional and global average sea level change remain a focus of climate change research. One complication in obtaining coherent estimates is that geodetic datasets measure different aspects of the sea level field. Satellite altimetry constrains changes in the sea surface height (SSH; or absolute sea level), whereas tide gauge data provide a measure of changes in SSH relative to the crust (i.e., relative sea level). The latter is a direct measure of changes in ocean volume (and the combined impacts of ice sheet melt and steric effects), but the former is not since it does not account for crustal deformation. Nevertheless, the literature commonly conflates the two estimates by directly comparing them. We demonstrate that using satellite altimetry records to estimate global ocean volume changes can lead to biases that can exceed 15%. The level of bias will depend on the relative contributions to sea level changes from the Antarctic and Greenland Ice Sheets. The bias is also more sensitive to the detailed geometry of mass flux from the Antarctic Ice Sheet than the Greenland Ice Sheet due to rotational effects on sea level. Finally, in a regional sense, altimetry estimates should not be compared to relative sea level changes because radial crustal motions driven by polar ice mass flux are nonnegligible globally.

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