Dust Logger as a Tool for Regional Correlations: New South Pole Age vs. Depth

The South Pole is a uniquely isolated location from which no deep ice core has yet been collected; however, by using high resolution dust logs created during the commissioning of the IceCube Neutrino Observatory we have managed to create a well resolved age versus depth relationship for this site. The dust logs (~3 mm/sample) were collected down to 2440 m by lowering logging equipment down two hot water drilled boreholes and have allowed for the identification of numerous dust and volcanic markers. By matching the dust to similar features recorded in the previously dated EPICA Droning Maud Land (EDML) core (Ruth et al. 2005) and volcanic ash layers to widespread layers known at other Antarctic sites, we have derived an age vs. depth profile for South Pole. This technique holds considerable promise for cross-correlation of other ice cores at regional scales. At South Pole, we arrive at an age of 34 kyr at 1400 m (near the onset of bubble free ice), of 92 kyr at 2400 m depth and an extrapolated near bedrock age of ~150 kyr at 2800 m depth. The apparent layer thickness decreases approximately monotonically from ~11 cm/yr near the surface, to ~2.5 cm/yr at 1400 m and ~1 cm/yr at 2400 m with a possible abrupt shift near the glacial-interglacial transition. The South Pole position on a slope with large local flow velocity (~9 m/yr) allows for unique studies of flow driven deformation and tests of glaciological models. The existing South Pole dust logs suggest that small variations in dust content have resulted in appreciable internal deformations within the ice sheet. Despite this, it appears that the depth-depth relationship between South Pole and EDML is well approximated by a simple polynomial function over most of its range. The use of high resolution dust logging data can be a powerful tool in establishing regional scale correlations between ice cores. Preliminary work has shown that the GRIP and GISP2 boreholes can also be correlated in this way. Combined with timing information, the sub-cm resolution of the dust logger may offer new opportunities to understand climate change on very short timescales and to test theories of leads and lags within the global climate system. Ruth, U., et al., Geophysical Research Abstracts 7, 07490 (2005).