Since their discovery, subglacial lakes beneath the Antarctic ice sheet have been a focus of scientific curiosity and study. It has been postulated that subglacial lakes present a viable habitat for microbial life and are underlain by sediments containing a record of changes in the ice sheet above. Subglacial Lake Ellsworth, West Antarctica, is the subject of a continued project aiming to achieve clean access in order to explore these hypotheses. One of the key outcomes of lake sampling is to establish the hydrochemistry, from which deductions about the limnology of the system can be made. A new theoretical insight into the hydrochemistry of subglacial lakes is achieved through reanalysis of the geochemical dataset published from meteoric and accretion ice from above Subglacial Lake Vostok, East Antarctica. It is shown that Subglacial Lake Vostok is a well-mixed system at steady-state. Of the flux of water to the lake, ~60% drains away from the lake and ~40% freezes at the ice-water interface. A downstream subglacial hydrological catchment is strongly indicated. An average cationic denudation rate of ~9meq∑+·m-2·yr-1 is inferred at the lake-sediment interface. The methods and outcomes of the Subglacial Lake Vostok model form the theoretical basis to scope the controls on the hydrochemistry of Subglacial Lake Ellsworth. A hydrologically open lake system leads to dilute, isotopically heavier water. A hydrologically more isolated lake system results in more concentrated waters with a stable water isotope composition that is removed from the local meteoric water line. Geochemical weathering reactions are expected to contribute the majority of dissolved ionic species and meteoric ice is shown to deliver oxygen and nitrogen to the lake. The model results provide a theoretical framework for the interpretation of analyses from lake water samples. The model results are also used to guide a sampling and analysis strategy which would optimise the scientific gains of subglacial lake sampling. The precise nature of the processes within Subglacial Lakes Ellsworth and Vostok remain untested, but this thesis provides a robust basis for interpreting the hydrochemistry of both lakes.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:665174 |
| Date | January 2014 |
| Creators | Harris, William Noel Laurence |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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