Melting, freezing, ice deformation, and ice flow at Lake Vostok: An analysis of ice-penetrating radar data
Abstract
We present evidence for melting and freezing at Lake Vostok in our analysis of ice-penetrating radar data collected in the 2000-2001 field season. The dense coverage in the dataset (7.5 km spacing of the east-west lines, and 11.25-22.5 km spacing in the north-south lines) over the 14,000 km^2 lake allowed us to identify continuous horizons over the survey area in 3-D. Melting is interpreted in the thinning of the internal layers with respect to the lake surface and is most dominant in the northern third of the lake. The internal layers, changes in electric conductivity associated with increased precipitation of volcanic dust, represent isochrons. The melting is on the order of 1 cm/yr consistent with thermodynamic constraints. Basal melting feeding an East Antarctic subglacial lake has only been identified previously at Lake Concordia in the vicinity of Dome C. Freezing is interpreted both from the thickening of internal layers with respect to the lake surface along flow and the presence of an accretion ice reflector in the radar data. Freezing is dominant in the southern half of the lake at rates of about 1 cm/yr as we have presented earlier. The observation of melting in the north and freezing in the south is consistent with the predictions for pressure dependent freezing being controlled by the thicker ice thickness in the north compared to the thinner ice above the lake in the south. We are also able to identify distinctive structures in the internal layers over the lake inherited from the basal topography on the western upstream shore of the lake to track the ice flow. Over the northern part of the lake we observe flow divergence with respect to the southern part of the lake possibly related to an ice divide east of the lake. Internal deformation, reflected in the changes in relative ice thickness between internal layers, is more pronounced in the northern half of the lake.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA....12927T