Field study and remote sensing measurements of an area of snow megadunes on the East Antarctic plateau provides a preliminary assessment of dune morphology, firn structure, and layering in the features. Snow megadunes are undulating variations in accumulation and surface texture, with wavelengths of 2 to 5 km and amplitudes up to 5 meters. The features cover 500,000 km2 of the East Antarctic plateau, occurring in areas of moderate regional slope and low accumulation on the flanks of the ice sheet between 2500 and 3800 meters elevation (Fahnestock et al., 2000). Our field area lies in the Byrd Glacier catchment region, near 80.78 degrees S, 124.5 degrees E, at an elevation of 2885 meters. Crest to crest separation near the field site averages 4.2 km. GPS topographic profiles show a 4 to 5 meter surface amplitude on a regional slope of about 0.001. This region contains some of the best examples of the megadune features that could be found in satellite mappings. Landsat images and aerial photography indicate the dunes consist of alternating surfaces of glaze and rough sastrugi with gradational boundaries. This pattern is oriented perpendicular to the mean wind direction, as modeled in katabatic wind studies (and partly confirmed by our brief observations). Glaze surfaces cover the leeward faces and troughs; rough sastrugi cover the windward faces and crests. The megadune pattern is crossed by smooth to eroded wind-parallel longitudinal dunes. Wind-eroded longitudinal dunes form spectacular 1-meter-high sastrugi in nearby areas. Dune structure at depth was profiled by ground-penetrating radar. The profile shows a sub-surface wave structure with amplitude of 5 to 8 m and a shift in the crest/trough pattern with depth consistent with upwind accretionary migration of the rough sastrugi patches. The layer pattern also indicates greatly reduced accumulation in glaze areas. The dune wave pattern is visible to the base of the profile, 40 meters below the surface. Given the very low accumulation rates for the area (1 to 4 cm at Vostok and nearby IGY-era snowpit studies), this thickness may represent the last few thousand years.

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• scambos_0125570

SCIOPS Short Name: scambos_0125570 Version ID: Not provided Unique ID: C1214621845-SCIOPS

This dataset provides an ice velocity map for the whole Greenland ice-sheet for the winter of 2013-2014, derived from RADARSAT-2 data, as part of the ESA Greenland Ice Sheet Climate Change Initiative (CCI) project. The ice velocity data were derived from intensity-tracking of RADARSAT-2 data aquired between 21/1/2014 and 02/04/2014. The data are provided on a polar stereographic grid (EPSG3413: Latitude of true scale 70N, Reference Longitude 45E). The horizontal velocity is provided in true meters per day, towards the Eastings and Northings direction of the grid; the vertical displacement, derived from a digital elevation model, is also provided. Both a single NetCDF file (including all measurements and annotation), and separate geotiff files with the velocity components are provided. This product was generated by DTU Space - Microwaves and Remote Sensing.

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• 9bdeb99d91a743fe84623264587ad043

FEDEO Short Name: 9bdeb99d91a743fe84623264587ad043 Version ID: NA Unique ID: C2548142863-FEDEO

The aim of the project was to derive a number of control points that could be used to georeference two Radarsat scenes over Heard Island. Control points were derived from aerial photography covering various locations around the island, namely: Cape Gazert, Atlas Cove, Brown Lagoon, Manning Lagoon and Winston Lagoon. ERDAS Imagine with OrthoBase Pro photogrammatric software was used to ortho-rectify the aerial photography and extract values for the derived control points. ERDAS Imagine OrthoRadar was used to georeference the Radarsat images. The measurements taken from the aerial photography have been described in an earlier report.

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• Heard_RadarSat_georef

AU_AADC Short Name: Heard_RadarSat_georef Version ID: 1 Unique ID: C1214313518-AU_AADC

This data set provides maps of snow cover and sea ice for the Northern Hemisphere from February 1997 to the present from the United States National Ice Center (USNIC). USNIC analysts produce these using the Interactive Multisensor Snow and Ice Mapping System (IMS). Maps are derived from a variety of data products including satellite imagery and in situ data. The data are provided in ASCII text, GeoTIFF, and NetCDF formats in three different resolutions: 1 km, 4 km, and 24 km. Note: The IMS product is considered an operational product; however, USNIC, who creates this product, does not guarantee availability or timely delivery of data via the NIC Web server. NSIDC, as the data archive, does not guarantee availability of this product via the NSIDC Web server. These servers should not be used to support operational observation, forecasting, emergency, or disaster mitigation operations, either public or private. Users with real-time operational needs should visit the USNIC Web site and contact the USNIC Liaison to request access to their operational server.

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NSIDCV0 Short Name: G02156 Version ID: 1 Unique ID: C1386246258-NSIDCV0

Metadata record for data from ASAC Project 2318 See the link below for public details on this project. ---- Public Summary from Project ---- This project is a cooperative venture between Australian and Italian institutes in a study of the mass budget of a large sector of the East Antarctic ice sheet. The mass budget represents the difference between the net input of moisture from the ocean as snow accumulating on the surface and the discharge of ice from the grounded part of the ice sheet. Any mismatch between these input and out put terms produces a direct contribution to change in sea level. Measurements of ice thickness along the coastal margin of the grounded ice sheet, combined with velocity data derived from satellite remote sensing methods, will provide the first direct measurements of the total mass output for the part of the ice sheet draining through this sector of the coastline. The observations will also a baseline against which future change in the mass flux can be assessed. From the abstract of the referenced paper: An air-borne radio echo sounding survey was conducted over the Amery Ice Shelf, East Antarctica, in December 2003. Nine transverse profiles where obtained approximately normal to the flow of direction, together with one longitude profile for a total length of of flight lines of about 1000km. We determined the spatial distribution of the characteristics of the RES signal returned from the ice-water interface at the base of the shelf. The key characteristics are described by the amplitude of the echo and the slope of the leading edge of the returned pulse. For the mass flux we ice thickness values extracted from our RES data, and velocities derived form InSAR maximum coherence tracking in pairs of Radarsat SAR images, with control provided by surface measurements. We calculate the mass budget for a set of discrete areas bounded by our RES survey lines across the shelf, and flow-lines derived from the velocity field (modified in the across shelf components of the velocity) and from linear flow-features identified in the satellite images. using available estimates of the snow accumulation rate at the upper surface, and assuming the ice thickness and velocities are stationary in time, we attribute the mass imbalance within a sub-area to be the result of melt or freeze at the base of the shelf. Both, the distribution of values of melt-freeze rates, and of the characteristics basal echoes form distinct patterns that appear to be influenced by variations in the ice draft and conditions in the sub-shelf ocean cavity. We find a net melt regime associated with the deeper draft to the South and under the central part of the shelf, and net freeze conditions in the North and sides, particularly towards the western margin. the strength of the electromagnetic signals reflected from the ice water-interface shows a similar pattern of variation along all nine transverse profiles. We find a strong association with basal mass balance Summary of progress 2004/2005 The field phase of the project was completed in 03/04 season. Current work involves analysis and interpretation of the Radio Echo Sounding measurements of ice thickness. An initial appraisal was completed of all RES data. A coarsely-spaced set of preliminary estimates of ice thickness were extracted and merged with GPS position data for generation of a first-cut distribution of ice thickness round a large sector of the ice sheet margin. New analysis systems have been developed and to-date applied to 25% of the data for extraction of detail ice thickness information and characteristics of the radar echoes. An initial assessment of all the RES data collected during the field work has been completed. Preliminary ice thickness estimates have been extracted at coarse spacing along the flight lines to generate a first-cut assessment of the ice thickness distribution for planning next phases of the project and for assessment of the need for additional field work. Those data have been merged with GPS position data collected at a ten-second time-interval along the flight track. This work has been carried out primarily by the Italian investigators. In Australia, software systems have been developed to carry out the full-resolution analysis of the digital RES data. This analysis system is based on developments undertaken in AAS project # 2224. To-date, data analysis using this system has been completed for all flights over the Amery Ice Shelf, and analysis of flights over the Law Dome, Totten Glacier, Moscow University Ice Shelf is nearing completion. As part of the depth extraction procedure, algorithms have been developed and implemented that allow extraction of the echo characteristics for an horizon identified in the digital record. For the echoes forming that horizon, the leading-edge slope, peak and base power, echo-width, and height are extracted. These characteristics vary with the characteristics of the reflector in the ice and can be related to roughness, reflectivity coefficient (dielectric contrast), etc. For the flight lines over the Amery Ice Shelf we have found a spatially coherent pattern in the variation in the echo-height and leading-edge-slope of the basal echo that appears to correspond to variation between individual flow-bands of reflection properties of the ice-water interface. This is a recent preliminary finding and work is continuing with these aspects. This detail analysis phase of the project is being carried out jointly by N Young and A Forieri during a 5-month visit by A Forieri to the ACE CRC funded by PNRA (Italy) and ACE CRC.

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• ASAC_2318

AU_AADC Short Name: ASAC_2318 Version ID: 1 Unique ID: C1214312644-AU_AADC