United Kingdom National Report
Prepared by: Robert Mulvaney
1. Ice cores
During January 1998, we collected a 122m ice core at the BAS EPICA Fuel Depot (S7702.39', W01030.08'). Borehole close-off was reached at about 74m with a 10m temperature of -37.7C and around 7cm water equivalent accumulation. A borehole temperature profile was measured by 3 calibrated thermistors. A series of four 10m satellite cores were drilled 5km to the south, west, east and north (M2, 3, 4, 5) of the main borehole to assess the local spatial variability of the ice core records. A further series of five 20m ice cores were drilled on a traverse to the east and west of the main borehole: to the east 100km (M6), and to the west at 100, 200, 300 and 365km (M7, 8, 9, 10) from the BAS Fuel Depot main drilling site. These cores are intended to characterise the spatial gradient in chemistry and physical characteristics across the western DML region. All these cores are/will be analysed for the major anions and cations, DEP, ECM. Each site had an accumulation rate of between 6 and 7cm water per annum, implying that the 122m core spans a period of 1300 years, while the 20m cores span 130 years.
Table 1: Ice cores collected by BAS during January 1998
|Date drilled||Core Location||Depth / m||10m temperature|
|M1||Jan 98||BAS Fuel Depot
S 7702.39' W 01030.08'
|M2||2/1/98||Satellite core South
S 7705.49' W 01029.35'
|M3||2/1/98||Satellite core West
S 7703.72' W 01042.29'
|M4||3/1/98||Satellite core East
S 7702.53' W1019.52'
|M5||4/1/98||Satellite core North
S 7700.19' W 01033.36'
|M6||20 - 21/1/98||Eastern traverse, site 1
S 7700.62' W 00640.38'
|M7||30/1/98||Western traverse, site 1
S 7710.94' W 01454.74'
|M8||1/2/98||Western traverse, site 2
S 7720.80' W 01833.26'
|M9||3/2/98||Western traverse, site 3
S 7700.62' W 02217.43'
|M10||4-5/2/98||Western traverse, site 4
S 7700.92' W 02422.74'
2. Strain network
A series of 10 stakes were placed in an array of diameter 14 km around the BAS Fuel Depot, and located by kinematic and static GPS techniques. Post-processing the occupations with GPS base station data from AWI and Nordic DML activities, plus SANAE station data (crucial dates are 19-21 January and 1 - 8 February) will give the precise positions that will enable flow measurement to be calculated following future re-measurement. The stakes are likely to survive visible for up to 10 years in this area. The stakes were re-surveyed in the 98/99 season showing a flow of 3m per year towards the south-west, draining into the Bailey Ice Stream.
3. Automatic collection of aerosols (ASSAY)
Automated System for Sampling Aerosol Year-round. This system (PI: Eric Wolff/BAS) samples aerosols by continuously pumping air through a sequence of aerosol filters (Teflon/nylon/nylon) throughout the year. Filter packs are changed every two weeks automatically. The filters were retrieved and fresh filter packs installed in Jan 99, and the filters retrieved and the system uplifted in Jan 00. Analysis of a range of anions and cations collected by the filters will give the aerosol loading of the air which will be related to the levels of these species observed in the ice core at the same site.
4. Ground Penetrating Radar survey
During an overland traverse towards the west (approximately along the ice divide) by skidoo we collected a continuous GPR profile using a Pulse-Ekko 1000 radar system. The system and logging PC was mounted on the rear of a skidoo, and the Tx/Rx antenna towed 27m behind. General conditions: 900 MHZ frequency, 100ps sampling interval, 250ns time window, penetration depth approx 25m. Returns were collected approximately every second, or 1m resolution along the track. The profile is continuous along the 365km traverse. Geolocation is via kinematic GPS. The traverse passed through each of the four 20m ice core sites.> At each site, additional GPR surveys were made, including common mid-point experiments at 900, 450 and 225MHz, additional higher horizontal resolution profiles (approx 0.2m along track) around the boreholes, reflections from metal rods inserted in a snow pit wall, reflections from rods lowered down the borehole. An example of a 0.2m resolution along-track radar profile from near the M9 borehole is shown in figure 2 (crudely processed at this stage).
The radar data indicate the local spatial noise in the accumulation signal around the borehole. If a single reflector can be followed across the traverse, it may be possible to produce an accumulation profile along ice divide. In addition, we will compare the radar data with the physico-chemical data from the ice cores.
5. Heavy metal samples
Samples for heavy metal analysis were collected for Prof Scarponis group in Venice. A vertical profile of samples were removed from a 1.85m wall of a freshly dug pit in 15 precleaned polyethylene, and 36 precleaned PTFE vials. The pit was located at S7701.7', W01042.5', 5km upwind to the NW of the BAS Depot camp site.
6. Firn-air samples
Firn-air samples were pumped from the borehole at regular intervals until pore close-off for the EU funded project FIRETRACC/100 [Firn record of trace gases relevant to atmospheric chemical change over 100 years). Firn-air was pumped from 18 discrete depths in the borehole as drilling progressed and compressed into a series of up to 5 flasks for each level. Analysis of a suite of gases will be carried out at five European institutes (University of East Anglia; Max Plank Institute, Mainz; Laboratoire de Glaciologie et Geophysique de LEnvironnement; University of Bern; Centre des Faibles Radioactivites).