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EARTH SCIENCE > Cryosphere > Glaciers/Ice Sheets

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  • 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.

  • Meteorological data collected on Larsen Ice Shelf including pressure, temperature, wind speed and direction.

  • 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.

  • This dataset was collected during two Antarctic field seasons (2013-14, 2014-15) using the DEep LOoking Radio-Echo Sounder (DELORES), a ground-based ice-penetrating radar system that was designed and built by the British Antarctic Survey. It is an updated version of the radar used by Hindmarsh and others (2011). The system emits 2500 radio-wave pulses per second with a centre frequency of 4 MHz and samples the return at 250 MHz. Vertical resolution is approximately 30 cm. The radar is towed across the ice-sheet surface behind a skidoo at approximately 15 km h -1 and 512 complete traces are staked for each stored record, resulting in stacked traces approximately every 85 cm.

  • This data was collected during two Antarctic field seasons (2013-14, 2014-15) using two Leica GS10 dual-frequency Global Position Systems (dGPS). We installed 53 2m aluminium stakes in the snow surface along lines perpendicular to ice divides on four ice rises in the Ronne Ice Shelf region. In each season we used the dGPS units to measure the position of each pole. During most position measurements we deployed a rover unit for 20 minutes at each stake while a static base station dGPS unit was left in place for 5 or more hours. In the minority of cases the power to the base station unit failed and data from the rover unit is not accompanied by base-station data.

  • 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. Expect no core to remain once analysis has been completed.

  • Seismic reflection data acquired in the region of subglacial Lake Ellsworth. Recording instrument: Geometrics Geode, 48 channels, active source (explosives). Five single-fold lines. Line length between 7.7 and 2.5 km. In addition, fold increased to 4 for the central part of one line (over the lake itself). Dataset also includes data from a single shallow seismic refraction experiment.

  • 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.

  • 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.