DOI: 10.7280/d1gw91
title: Annual Ice Velocity of the Greenland Ice Sheet (1991-2000)

description: We derive surface ice velocity using data from 16 satellite sensors
 deployed by 6 different space agencies. The list of sensors is given in
 the Table S1. The SAR data are processed from raw to single look complex
 using the GAMMA processor (www.gamma-rs.ch). All measurements rely on
 consecutive images where the ice displacement is estimated from tracking
 or interferometry (Joughin et al. 1998, Michel and Rignot 1999, Mouginot
 et al. 2012). Surface ice motion is detected using a speckle tracking
 algorithm for SAR instruments and feature tracking for Landsat. The
 cross-correlation program for both SAR and optical images is ampcor from
 the JPL/Caltech repeat orbit interferometry package (ROI_PAC). We assemble
 a composite ice velocity mosaic at 150 m posting using our entire speed
 database as described in Mouginot et al. 2017 (Fig. 1A). The ice velocity
 maps are also mosaicked in annual maps at 150 m posting, covering July,
 1st to June, 30th of the following year, i.e. centered on January, 1st
 (12) because a majority of historic data were acquired in winter season,
 hence spanning two calendar years. We use Landsat-1&2/MSS images
 between 1972 and 1976 and combine image pairs up to 1 years apart to
 measure the displacement of surface features between images as described
 in Dehecq et al., 2015 or Mouginot et al. 2017. We use the 1978 2-m
 orthorectified aerial images to correct the geolocation of Landsat-1 and
 -2 images (Korsgaard et al., 2016). Between 1984 and 1991, we process
 Landsat-4&5/TM image pairs acquired up to 1-year apart. Only few
 Landsat-4 and -5 images (~3%) needed geocoding refinement using the same
 1978 reference as used previously. Between 1991 and 1998, we process radar
 images from the European ERS-1/2, with a repeat cycle varying from 3 to 36
 days depending on the mission phase. Between 1999 and 2013, we used
 Landsat-7, ASTER, RADARSAT-1/2, ALOS/PALSAR, ENVISAT/ASAR to determine
 surface velocity (Joughin et al., 2010; Howat, I. 2017; Rignot and
 Mouginot, 2012). After 2013, we use Landsat-8, Sentinel-1a/b and
 RADARSAT-2 (Mouginot et al., 2017). All synthetic aperture radar (SAR)
 datasets are processed assuming surface parallel flow using the digital
 elevation model (DEM) from the Greenland Mapping Project (GIMP; Howat et
 al., 2014) and calibrated as described in Mouginot et al., 2012, 2017.
 Data were provided by the European Space Agency (ESA), the EU Copernicus
 program (through ESA), the Canadian Space Agency (CSA), the Japan
 Aerospace Exploration Agency (JAXA), the Agenzia Spaziale Italiana (ASI),
 the Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR) and the National
 Aeronautics and Space Administration (NASA). SAR data acquisitions were
 coordinated by the Polar Space Task Group (PSTG). Errors are estimated
 based on sensor resolution and time lapse between consecutive images as
 described in Mouginot et al. 2017.  References Dehecq, A,
 Gourmelen, N, Trouve, E (2015). Deriving large-scale glacier velocities
 from a complete satellite archive: Application to the
 Pamir-Karakoram-Himalaya. Remote Sensing of Environment, 162,
 55-66.  Howat IM, Negrete A, Smith BE (2014) The greenland ice
 mapping project (gimp) land classification and surface elevation data
 sets. The Cryosphere 8(4):1509-1518. Howat, I (2017). MEaSUREs Greenland
 Ice Velocity: Selected Glacier Site Velocity Maps from Optical Images,
 Version 2. Boulder, Colorado USA. NASA National Snow and Ice Data Center
 Distributed Active Archive Center.  Joughin, I., B. Smith, I.
 Howat, T. Scambos, and T. Moon. (2010). Greenland Flow Variability from
 Ice-Sheet-Wide Velocity Mapping, J. of Glac.. 56. 415-430. 
 Joughin IR, Kwok R, Fahnestock MA (1998) Interferometric estimation of
 three dimensional ice-flow using ascending and descending passes. IEEE
 Trans. Geosci. Remote Sens. 36(1):25-37. Joughin, I, Smith S, Howat I, and
 Scambos T (2015). MEaSUREs Greenland Ice Sheet Velocity Map from InSAR
 Data, Version 2. [Indicate subset used]. Boulder, Colorado USA. NASA
 National Snow and Ice Data Center Distributed Active Archive Center.
 Michel R, Rignot E (1999) Flow of Glaciar Moreno, Argentina, from
 repeat-pass Shuttle Imaging Radar images: comparison of the phase
 correlation method with radar interferometry. J. Glaciol. 45(149):93-100.
 Mouginot J, Scheuchl B, Rignot E (2012) Mapping of ice motion in
 Antarctica using synthetic-aperture radar data. Remote Sens.
 4(12):2753-2767. Mouginot J, Rignot E, Scheuchl B, Millan R (2017)
 Comprehensive annual ice sheet velocity mapping using landsat-8,
 sentinel-1, and radarsat-2 data. Remote Sensing 9(4). Rignot E, Mouginot J
 (2012) Ice flow in Greenland for the International Polar Year 2008- 2009.
 Geophys. Res. Lett. 39, L11501:1-7.