The dataset is an improved, high resolution ice shelf freeboard, thickness and draught product for Ekström, Jelbart, Fimbul, Vigrid and Nivlisen ice shelves in Dronning Maud Land, East Antarctica. It is based on high resolution (8 m) digital elevation model (DEM) strips from WorldView stereo-satellite image pairs used to create the Reference Elevation Model of Antarctica (REMA) mosaic (Howat et al., 2019). The standard mosaic product suffers from artifacts where ice shelf features such as rifts, the surface expressions of basal channels or crevasses, and the calving front are discontinuous as a result of the advection of features with ice flow between the time of different image acquisitions. Here, NASA ITS_LIVE ice flow velocity mosaics (Gardner et al., 2018) and the ArcMap/Python Warp tool were used to shift DEM tiles up or down the glacier flow field to a common reference date (based on the austral summer maximal DEM coverage of the grounding zone), then corrected for elevation biases and tilts in the vertical dimension using the offsets to CryoSat-2 derived Point of Closest Approach elevations (Gray et al., 2015; 2017), before being mosaicked. WGS84 ellipsoidal heights were converted to freeboard using the EIGEN6C4 geoid (Förste et al., 2014) and an ocean Mean Dynamic Topography of -1.3 m (Andersen et al., 2015). Freeboard was converted to thickness and draught using the assumption of hydrostatic equilibrium (density of ice 917 kg/m^3, density of seawater 1027.5 kg/m^3) and an upsampled Firn Air Content (FAC) field (Ligtenberg et al., 2011). FAC was limited to 50% of freeboard in some marginal areas and ice filled rifts to prevent physically unrealistic ice thicknesses, an artifact of the oversampling of the FAC field. In addition, some discontinuities of small-scale features may persist.
References:
Howat, I. M., Porter, C., Smith, B. E., Noh, M.-J., and Morin, P.: The Reference Elevation Model of Antarctica, The Cryosphere, 13, 665–674, https://doi.org/10.5194/tc-13-665-2019, 2019.
Gardner, A. S., M. A. Fahnestock, and T. A. Scambos, [2020]: ITS_LIVE Regional Glacier and Ice Sheet Surface Velocities: Version 1. Data archived at National Snow and Ice Data Center; https://doi:10.5067/6II6VW8LLWJ7. 2019.
Gray, L., Burgess, D., Copland, L., Demuth, M. N., Dunse, T., Langley, K., and Schuler, T. V.: CryoSat-2 delivers monthly and inter-annual surface elevation change for Arctic ice caps, The Cryosphere, 9, 1895–1913, https://doi.org/10.5194/tc-9-1895-2015, 2015.
Gray, L., Burgess, D., Copland, L., Dunse, T., Langley, K., and Moholdt, G.: A revised calibration of the interferometric mode of the CryoSat-2 radar altimeter improves ice height and height change measurements in western Greenland, The Cryosphere, 11, 1041–1058, https://doi.org/10.5194/tc-11-1041-2017, 2017.
Förste, C., Bruinsma, S. L., Abrykosov, O., Lemoine, J.-M., Marty, J. C., Flechtner, F., Balmino, G., Barthelmes, F., Biancale, R.: EIGEN-6C4 The latest combined global gravity field model including GOCE data up to degree and order 2190 of GFZ Potsdam and GRGS Toulouse. GFZ Data Services. https://doi.org/10.5880/icgem.2015.1, 2014.
Andersen, O., Knudsen, P., Stenseng, L.: The DTU13 MSS (Mean Sea Surface) and MDT (Mean Dynamic Topography) from 20 Years of Satellite Altimetry. In: Jin, S., Barzaghi, R. (eds) IGFS 2014. International Association of Geodesy Symposia, vol 144. Springer, Cham. https://doi.org/10.1007/1345_2015_182, 2015
Ligtenberg, S. R. M., Helsen, M. M., and van den Broeke, M. R.: An improved semi-empirical model for the densification of Antarctic firn, The Cryosphere, 5, 809–819, https://doi.org/10.5194/tc-5-809-2011, 2011.