EARTH SCIENCE > Cryosphere > Glaciers/Ice Sheets

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  • Over 20,000 km of new aerogravity data were acquired over Palmer Land during the 2002-2003 Antarctic campaign. Profile lines were oriented E-W with N-S tie lines. Line spacing was 5 km, tie lines were 25 km apart and nominal flight altitude was 2800 m. Differential, carrier phase, kinematic GPS processing methods provided the vertical and horizontal accelerations, which dominate the raw aerogravity signal. Levelled airborne gravity data have mean accuracies of 3 mGal. We present here the processed line aerogravity data collected using Lacoste and Romberg air-sea gravity meter S83. Data are provided as XYZ ASCII line data.

  • Gravity, magnetic and radar data were acquired during a joint UK-Argentina (BAS/IAA) project, during the austral summer 1998-1999. 10,771 line km of data were acquired using a BAS Twin Otter, covering an area of 21,000 km2 that comprises the James Ross Island archipelago and the NW corner of the Weddell Sea. Gravity and magnetic data were simultaneously acquired at a constant barometric height of 2000 m, providing a terrain clearance of approximately 100 m over the highest peaks. The main flight lines were flown along an E-W direction with 2000 m spacing over James Ross Island and at 4000 m interval offshore. Tie lines, oriented meridionally, were spaced 10,000 m and extended beyond the magnetic survey to provide a regional context to the survey area as required also for airborne gravity data analysis. Magnetic data were acquired at a frequency of 10 Hz using vapour cesium magnetometers mounted on the aircraft wing tips, and resampled to 1 Hz after compensation for manoeuvre noise. A triaxial fluxgate magnetometer was mounted close to the tail of the aircraft, providing magnetic attitude information used in the data compensation. However, gravity acquisition defines that turbulent conditions are avoided and so manoeuvre noise is generally minimal. Ashtech Z12 duel frequency GPS receivers were used for survey navigation and for post-processing of the GPS data. Magnetic data were de-spiked to remove avionics noise and then smoothed (- 300 m low pass filter), before re-sampling from 10 to 1 Hz. The data were first corrected for diurnal variations using low-pass filtered base station data (30 min low-pass filter). For the internal field we used the Definitive Geomagnetic Reference Field Model 1995. The final data processing step was network levelling and microlevelling (Ferraccioli et al., 1998). We present here the processed line aeromagnetic data collected using scintrex cesium magnetometers mounted on the BAS aerogeophysical equipped Twin Otter. Data are provided as XYZ ASCII line data.

  • During the austral summer of 2001/02 five thousand line kilometres of airborne radio echo sounding and aeromagnetic data were collected in the region of three tributaries of Slessor Glacier, East Antarctica, which drains into the Filchner Ice Shelf. We present here the processed bed elevation picks from airborne radar depth sounding acquired using the BAS aerogeophysicaly equipped Twin Otter aircraft. Data are provided as XYZ ASCII line data. Data were collected as part of UK Natural Environment Research Council (NERC) grant GR3/AFI2/65

  • During the 2001-02 field season a regional survey was flown on a 10 km line spacing grid over the drainage basin of the Rutford Ice stream (West Antarctica), as part of the TORUS (Targeting ice stream onset regions and under-ice systems) project. We present here the bed elevation picks from airborne radar depth sounding collected using the "BAS-built" radar depth sounding system mounted on the BAS aerogeophysical equipped Twin Otter aircraft. Data are provided as XYZ ASCII line data

  • This dataset contains a series of point measurements made using a ground-based phase-sensitive radio-echo sounder (pRES) designed by the British Antarctic Survey. The system is configured as a step-frequency radar to sample the frequency response of the ice at 3201 equally-spaced frequency steps between 225 MHz and 385 MHz.

  • A high resolution survey was flown opportunistically by BAS at the end of the AGAP aerogeophysical campaign during the 2008-09 Antarctic field season with NSF support from McMurdo. The main purpose was to collect data on the ice shelf for a radar pre-site survey for a major planned international ANDRILL drilling campaign at Coulman High. Due to lack of appropriate funding levels from several countries this ANDRILL drilling project has been postponed ( but the site remains nevertheless a potentially interesting target for future geoscience studies. The Coulman High project aimed to explore the range of paleo-environments, ecosystems and tectonic events that affected the Ross Sea region as it transitioned from the warm, high-CO2 Greenhouse world typical of the Eocene into the lower-CO2 and highly variable Icehouse conditions of the Oligocene and early Miocene. The aeromagnetic data released here can be used together with more extensive pre-existing international datasets to help study rift-related magmatism, faulting and sedimentary basins in the region.

  • In 1998, aeromagnetic data over the Larsen Ice Shelf were acquired giving information about the geological structure beneath the ice shelf. We present here the processed line aeromagnetic data collected using scintrex cesium magnetometers mounted on the BAS aerogeophysical equipped Twin Otter. Data are provided as XYZ ASCII line data.

  • A British Antarctic Survey Twin Otter and survey team acquired 8,300 line-km of magnetic data during the Austral summer of 1998/99. Gravity and radio-echo data were acquired simultaneously with the magnetic data at a compromise constant barometric height of 2,200 m, which provides a terrain clearance of 100 m over the highest peaks. Two separate surveys were conducted; one at 5 km line spacing (tie lines at 20 km) over and stretching beyond the southern extent of the Forrestal range (main survey), and one at 2 km line spacing (tie lines at 8 km) covering the Dufek Massif (detailed survey). Wing-tip-mounted cesium vapour magnetometers acquired data at 10 Hz, which was resampled to 1 Hz after deletion of data corrupted by the radio echo transmissions. It is not possible to compensate the magnetic data for maneuver noise after this process as the data are under-;sampled with respect to maneuver noise. However, because gravity data was being acquired at the same time, turbulent conditions were avoided and so maneuver noise was at a minimum. Ashtech Z12 dual frequency GPS receivers were used for survey navigation. Pseudorange data were supplied to a Picodas PNAV navigation interface computer, which was used to guide the pilot along the pre-planned survey lines. The actual flight path was recovered, using carrier-phase, continuous, kinematic GPS processing techniques. All magnetic and pseudorange navigation data were recorded at 1 Hz on a Picodas PDAS 1000, PC-based data acquisition system. Data were de-spiked and then smoothed (~100 m low pass filter), before re-sampling from 10 to 1 Hz. The data were IGRF corrected, leveled and reduced to the pole in the field. A 2.5 km cell grid was produced. The negative bias to the anomaly amplitudes is a result of the poorly defined IGRF in this area. We present here the processed line aeromagnetic data acquired using scintrex cesium magnetometers mounted on the BAS aerogeophysical equiped Twin Otter. Data are provided as XYZ ASCII line data.

  • A distributed acoustic sensing (DAS) experiment was undertaken at SkyTrain Ice Rise in the Weddell Sea Sector of West Antarctica. The aim was to evaluate the use of DAS technology using existing infrastructure and for delineating the englacial fabric to improve our understanding of ice sheet history in the region. Three walkaway profiles were acquired at 45 degree intervals using a hammer and plate source. Both direct and reflected P- and S-wave energy, as well as surface wave energy, are observed using a range of source offsets recorded using fibre optic cable. Significant noise results from the cable hanging untethered in the borehole. At greater depth, where drilling fluid is present, signal strength is sufficient to measure seismic interval velocities and attenuation. Fieldwork was part of the BEAMISH Project (NERC AFI award numbers NE/G014159/1 and NE/G013187/1). John Michael Kendall was supported by additional funding from NERC award No. CASS-166. The Skytrain borehole and fibre optic cable are part of the University of Cambridge WACSWAIN Project (EU Horizon 2020 agreement No. 742224).

  • A coastline of Kalaallit Nunaat/ Greenland covering all land and islands, produced in 2017 for the BAS map ''Greenland and the European Arctic''. The dataset was produced by extracting the land mask from the Greenland BedMachine dataset and manually editing anomalous data. Some missing islands were added and glacier fronts were updated using 2017 satellite imagery. The dataset can be used for cartography, analysis and as a mask, amongst other uses. At very large scales, the data will appear angular due to the nature of being extracted from a raster with 150 m cell size, but the dataset should be suitable for use at most scales and can be edited by the user to exclude very small islands if required. The projection of the dataset is WGS 84 NSIDC Sea Ice Polar Stereographic North, EPSG 3413. The dataset does not promise to cover every island and coastlines were digitised using the data creator''s interpretation of the landforms from the images.