CryoSat-2 swath interferometric altimetry for mapping ice elevation and elevation change

Abstract For more than 25 years, satellite radar altimetry has provided continuous information on the state of the cryosphere and on its contribution to global sea-level rise. The technique typically delivers maps of ice-sheet elevation and elevation change with 3–10 km spatial resolution and seasonal to monthly temporal resolution. Here we show how the interferometric mode of CryoSat-2 can be used to map broad (5 km-wide) swaths of surface elevation with fine (500 m) spatial resolution from each satellite pass, providing a step-change in the capability of satellite altimetry for glaciology. These swaths of elevation data contain up to two orders of magnitude more surface elevation measurements than standard altimeter products, which provide single elevation measurements based on the range to the Point-Of-Closest-Approach (POCA) in the vicinity of the sub-satellite ground track. The swath elevations allow a more dense, statistically robust time series of elevation change to be formed with temporal resolution of a factor 5 higher than for POCA. The mean differences between airborne altimeter and CryoSat-2 derived ice sheet elevations and elevation rates range from −0.93 ± 1.17 m and 0.29 ± 1.25 m a−1, respectively, at the POCA, to −1.50 ± 1.73 m and 0.04 ± 1.04 m a−1, respectively, across the entire swath. We demonstrate the potential of these data by creating and evaluating elevation models of: (i) the Austfonna Ice Cap (Svalbard), (ii) western Greenland, and (iii) Law Dome (East Antarctica); and maps of ice elevation change of: (iv) the Amundsen Sea sector (West Antarctica), (v) Icelandic ice caps, and (vi) above an active subglacial lake system at Thwaites Glacier (Antarctica), each at 500 m spatial posting – around 10 times finer than possible using traditional approaches based on standard altimetry products.

[1]  Martin J. Siegert,et al.  A fourth inventory of Antarctic subglacial lakes , 2012, Antarctic Science.

[2]  Emmanuel Trouvé,et al.  Elevation Changes Inferred From TanDEM-X Data Over the Mont-Blanc Area: Impact of the X-Band Interferometric Bias , 2016, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing.

[3]  Freysteinn Sigmundsson,et al.  Segmented lateral dyke growth in a rifting event at Bárðarbunga volcanic system, Iceland , 2014, Nature.

[4]  Ian M. Howat,et al.  A new bed elevation dataset for Greenland , 2012 .

[5]  Malcolm McMillan,et al.  Seasonal evolution of supra-glacial lakes on the Greenland Ice Sheet , 2007 .

[6]  Robert N. Swift,et al.  Airborne Topographic Mapper Calibration Procedures and Accuracy Assessment , 2012 .

[7]  Ian Joughin,et al.  Fracture Propagation to the Base of the Greenland Ice Sheet During Supraglacial Lake Drainage , 2008, Science.

[8]  Duncan J. Wingham,et al.  Rapid discharge connects Antarctic subglacial lakes , 2006, Nature.

[9]  B. Smith,et al.  Connected subglacial lake drainage beneath Thwaites Glacier, West Antarctica , 2016 .

[10]  D. Vaughan,et al.  Extensive dynamic thinning on the margins of the Greenland and Antarctic ice sheets , 2009, Nature.

[11]  Helen Amanda Fricker,et al.  An Active Subglacial Water System in West Antarctica Mapped from Space , 2007, Science.

[12]  Eric Rignot,et al.  A Reconciled Estimate of Ice-Sheet Mass Balance , 2012, Science.

[13]  L. Phalippou,et al.  CryoSat: A mission to determine the fluctuations in Earth’s land and marine ice fields ☆ , 2006 .

[14]  Harihar Rajaram,et al.  Cryo‐hydrologic warming: A potential mechanism for rapid thermal response of ice sheets , 2010 .

[15]  G. Moholdt,et al.  Improved processing and calibration of the interferometric mode of the CryoSat radar altimeter allows height measurements of supraglacial lakes in west Greenland , 2016 .

[16]  Kate Snow,et al.  Channelized Melting Drives Thinning Under a Rapidly Melting Antarctic Ice Shelf , 2017 .

[17]  Ron Kwok,et al.  A Mini-Surge on the Ryder Glacier, Greenland, Observed by Satellite Radar Interferometry , 1996, Science.

[18]  A. Shepherd,et al.  Inland thinning of Pine Island Glacier, West Antarctica. , 2001, Science.

[19]  R. Cullen,et al.  Interferometric swath processing of Cryosat data for glacial ice topography , 2013 .

[20]  S. Carter,et al.  A revised inventory of Antarctic subglacial lakes , 2004, Antarctic Science.

[21]  Leigh A. Stearns,et al.  Increased flow speed on a large East Antarctic outlet glacier caused by subglacial floods , 2008 .

[22]  B. Smith,et al.  Brief Communication: Sudden drainage of a subglacial lake beneath the Greenland Ice Sheet , 2014 .

[23]  V. Helm,et al.  Ice‐sheet elevations from across‐track processing of airborne interferometric radar altimetry , 2009 .

[24]  Jonathan L. Bamber,et al.  A new 1 km Digital Elevation Model of the Antarctic Derived From Combined Satellite Radar and Laser Data , 2008 .

[25]  A. Shepherd,et al.  Surface elevation change and mass balance of Icelandic ice caps derived from swath mode CryoSat‐2 altimetry , 2016 .

[26]  Luke Copland,et al.  A revised calibration of the interferometric mode of the CryoSat-2 radar altimeter improves ice height and height change measurements in western Greenland , 2017 .

[27]  Marco Fornari,et al.  CryoSat-2 range, datation and interferometer calibration with Svalbard transponder , 2018, Advances in Space Research.

[28]  K. Langley,et al.  CryoSat-2 delivers monthly and inter-annual surface elevation change for Arctic ice caps , 2015 .

[29]  Jonathan L. Bamber,et al.  A new 1 km digital elevation model of Antarctica derived from combined radar and laser data – Part 2: Validation and error estimates , 2008 .

[30]  H. J. Zwally,et al.  Slope‐induced errors in radar altimetry over continental ice sheets , 1983 .

[31]  Emmanuel Trouvé,et al.  Evaluation of CryoSAT-2 for height retrieval over the Himalayan range , 2012 .

[32]  E. Lindstrom,et al.  Observing Systems Needed to Address Sea‐Level Rise and Variability , 2010 .

[33]  J G Marsh,et al.  Growth of Greenland Ice Sheet: Measurement , 1989, Science.

[34]  B. Smith,et al.  An inventory of active subglacial lakes in Antarctica detected by ICESat (2003–2008) , 2009, Journal of Glaciology.

[35]  Y. Arnaud,et al.  Contrasting patterns of early twenty-first-century glacier mass change in the Himalayas , 2012, Nature.

[36]  Willem Jan van de Berg,et al.  A high‐resolution record of Greenland mass balance , 2016 .

[37]  T. Scambos,et al.  The link between climate warming and break-up of ice shelves in the Antarctic Peninsula , 2000, Journal of Glaciology.

[38]  G. Marshall,et al.  Mass balance of the Antarctic ice sheet , 2006, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[39]  H. L. Miller,et al.  Climate Change 2007: The Physical Science Basis , 2007 .

[40]  N. Gourmelen,et al.  Four‐decade record of pervasive grounding line retreat along the Bellingshausen margin of West Antarctica , 2016 .

[41]  R. Scharroo,et al.  Antarctic elevation change from 1992 to 1996 , 1998, Science.

[42]  F. Sigmundsson,et al.  Gradual caldera collapse at Bárdarbunga volcano, Iceland, regulated by lateral magma outflow , 2016, Science.

[43]  Bo Sun,et al.  Bedmap2: improved ice bed, surface and thickness datasets for Antarctica , 2012 .

[44]  M. R. van den Broeke,et al.  A Reconciled Estimate of Glacier Contributions to Sea Level Rise: 2003 to 2009 , 2013, Science.

[45]  A. Shepherd,et al.  Three‐dimensional mapping by CryoSat‐2 of subglacial lake volume changes , 2013 .

[46]  X. Fettweis,et al.  Rapid dynamic activation of a marine‐based Arctic ice cap , 2014 .

[47]  Duncan J. Wingham,et al.  Increased ice losses from Antarctica detected by CryoSat‐2 , 2014 .

[48]  P. Skvarca,et al.  Larsen Ice Shelf Has Progressively Thinned , 2003, Science.

[49]  D. Marchant,et al.  The age and origin of the Labyrinth, western Dry Valleys, Antarctica: Evidence for extensive middle Miocene subglacial floods and freshwater discharge to the Southern Ocean , 2006 .

[50]  R. Francis,et al.  The European Space Agency’s Earth Explorer Mission CryoSat: measuring variability in the cryosphere , 2004, Annals of Glaciology.

[51]  X. Fettweis,et al.  Northeast sector of the Greenland Ice Sheet to undergo the greatest inland expansion of supraglacial lakes during the 21st century , 2016 .

[52]  Jack L. Saba,et al.  Mass changes of the Greenland and Antarctic ice sheets and shelves and contributions to sea-level rise: 1992-2002 , 2005 .

[53]  Finnur Pálsson,et al.  Glacier topography and elevation changes derived from Pléiades sub-meter stereo images , 2014 .