Site survey at Whitehall Glacier

Ground penetrating radar (GPR) measurements provide an image of the internal layering of a glacier and the topography of the ice-rock interface beneath. We applied low and high frequency radar pulses (8 MHz, 35 MHz, 200MHz, and 500MHz) to map the bedrock interface and internal flow structures in the glacier. Those features are identified through reflectors that result from changes in physical and chemical properties, such as dust layers or aerosol and density variations and are thought to represent isochrones (Morse et al., 1998; Vaughan et al., 1999). The choice of antenna frequency involves a trade-off between penetration depth and mapping resolution. The control units were mounted on a Nansen Sledge, pulling transmitter and transceiver antennae. The sledge also carried high precision GPS antenna, which is tied to the temporary GPS base station deployed at the WHG camp.

Traverses totaling approximately 80km have been surveyed with GPR. The measurements show that the glacier thickness exceeds 550m. Excellent isochrone reflections are visible in the top part of the profile, which will also be used to investigate geographical and chronological accumulation changes. Further post-processing will enhance the reflectors and will correct for surface topography. At MES a site survey was conducted during the 2003/04 field season.

Fig. 3 A) ASTER satellite image of Whitehall Glacier and vicinity. See Figure 1 for overview. Image from January 2005. Yellow flag indicates approximate location of proposed drilling site. Yellow arrows indicate approximate major flow lines. B) Digital elevation model. X/Y/Z grid in UTM 58 map units. Yellow grid indicate proposed ground penetrating radar survey lines (differential, 8, 35, 200, and 400 MHz)