EARTH SCIENCE > Cryosphere > Glaciers/Ice Sheets
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High resolution processed line aeromagnetic data over James Ross Island, Northern Antarctic Peninsula (1997/1998)
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.
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.
During the 1996-1997 Antarctic field season, an aeromagnetic survey was carried out by the BAS to the west of Alexander Island, designed to investigate the Charcot Island anomaly. The presented data was collected using wingtip mounted Caesium-vapour magnetometers. Magnetic effects due to aircraft motion were actively compensated using a triad of fluxgate magnetometers mounted in the tail of the aircraft. Data are provided as XYZ ASCII line data.
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
Processed bed elevation picks from airborne radar depth sounding across the region of three tributaries of Slessor Glacier, Coats Land, East Antarctica (2001/02 season)
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
High resolution processed line aerogravity data over James Ross Island, Northern Antarctic Peninsula (1997/1998)
Airborne gravity data were collected using a Zero Length Spring Corporation (ZLS)-modified LaCoste and Romberg model S air-sea gravimeter. The meter was mounted in a gyro-stabilised, shock mounted platform at the centre of mass of the aircraft to minimise the effect of vibrations and rotational motions. GPS data were recorded with an Ashtech Z12 dual frequency receiver in the aircraft and at a fixed base station. Differential, carrier phase, kinematic GPS methods were then used to calculate all the navigational information used for the dynamic corrections of the aerogravity data. Standard processing steps were taken to convert the raw gravity data to free air anomalies, including latitude, free air and Eotvos corrections. The vertical accelerations of the aircraft, which dominate the gravity signal recorded by the meter, were calculated by double differencing GPS height measurements. In addition, a correction was made for gravimeter reading errors caused by the platform tilting when it was subjected to horizontal accelerations (Swain, 1996). After making the above corrections, the data were low pass filtered for wavelengths less than 9 km to remove short wavelength noise from the geological signal. The data were continued to a common altitude of 2050 m and levelled. Cross-over analysis at 118 intersections yielded a standard deviation of 2.9 mGal, which is within the 1-5 mGal error range typically reported for airborne gravity surveys after levelling. Comparison between airborne measurements and previous land-based gravity data (Garrett, 1990), yielded an RMS difference of ~4.5 mGal, which is within the 2 sigma range for airborne gravity data accuracy.
Over 20,000 km of new aeromagnetic 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. Aeromagnetic processing included magnetic compensation, IGRF removal, diurnal correction, and levelling. Mean cross-over errors after microlevelling were <1 nT. Aeromagnetic data were gridded (1 km cell size) and reduced to the pole. 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.
As part of the International Thwaites Glacier Collaboration (ITGC) ~9540 km of new airborne gravity data was acquired by the British Antarctic Survey, including ~6200 km over the Thwaites Glacier catchment. Data was collected using an iCORUS strap-down airborne gravimeter system mounted on the BAS aerogeophysical equipped survey aircraft VP-FBL. The survey operated from Lower Thwaites Glacier camp, and focused on collecting data between 70 and 180 km from the grounding line. Additional profiles from the coast to the Western Antarctic Ice Sheet (WAIS) divide and over the eastern shear margin were also flown. Navigation, aircraft attitude, sensor temperature, initial and levelled free air gravity anomalies are provided as an ASCI table. The Thwaites 2019/20 aerogeophysical survey was carried out as part of the BAS National Capability contribution to the NERC/NSF International Thwaites Glacier Collaboration (ITGC) program. Data processing was supported by the BAS Geology and Geophysics team.
Analysis of shallow ice cores collected in the region of subglacial Lake Ellsworth. Three cores drilled to ~20 m depth. Two cores returned to UK for analysis. One core measured for density-depth in the field, then discarded. One of the two cores returned to UK has been sent to Bristol University for major anion/cation analysis; the other core is at the British Antarctic Survey (BAS) and will be analysed for accumulation rate. Density analysis is complete. Chemical analysis is complete. Accumulation analysis is in progress.
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.