7 research outputs found
Lakes beneath the ice sheet: The occurrence, analysis, and future exploration of Lake Vostok and other Antarctic subglacial lakes
Airborne geophysics has been used to identify more than 100 lakes beneath the ice sheets of Antarctica. The largest, Lake Vostok, is more than 250 km in length and 1 km deep. Subglacial lakes occur because the ice base is kept warm by geothermal heating, and generated meltwater collects in topographic hollows. For lake water to be in equilibrium with the ice sheet, its roof must slope ten times more than the ice sheet surface. This slope causes differential temperatures and melting/freezing rates across the lake ceiling, which excites water circulation. The exploration of subglacial lakes has two goals: to find and understand the life that may inhabit these unique environments and to measure the climate records that occur in sediments on lake floors. The technological developments required for in situ measurements mean, however, that direct studies of subglacial lakes may take several years to happen
Physiography and tectonic setting of the subglacial lake district between Vostok and Belgica subglacial highlands (Antarctica)
We present the interpretation of 11 radio echo-sounding (RES) missions carried out over the
Vostok–Dome Concordia region during the Italian Antarctic expeditions in the period 1995–
2001. The extension and the density of the radar data in the surveyed area allowed to reconstruct
a reliable subglacial morphology and to identify four relevant morphological structures namely:
the Aurora trench, the Concordia trench, the Concordia ridge and the South Hills. These
structures show evidence compatible with the presence of tectonic features. Morphological
considerations indicate their development in Cenozoic time. Hybrid cellular automata (HCA)-
based numerical modelling allowed to justify a possible role played by the tectonics of the
Aurora and Concordia trench evolution. This was accomplished by matching the bed profiles
along opportunely projected sections with the modelled surfaces as derived by the activity of
normal faults with variable surfaces within the continental crust. The Vostok–Dome C region
is characterized by a large number of subglacial lakes. From the analysis of basal reflected
power echo, we identified 14 new lakes and obtained information about their physiography as
well as their possible relations with tectonics.We propose a grouping of subglacial lakes on the
base of their physiography and geological setting, namely relief lakes, basin lakes and trench
lakes. Relief lakes located in the Belgica subglacial highlands and are characterized by sharp
and steep symmetric edges, suggesting a maximum water depth of the order of 100 m. Their
origin may well relate to localized, positive geothermal flux anomalies. Basin lakes located
in the Vincennes subglacial basin and are characterized by wider dimension that allow the
development of well-defined, flat ice surface anomalies. Trench lakes characterize the Aurora
and Concordia trenches as the possible effect of normal fault activity
Geological setting of the Concordia Trench-Lake system in East Antarctica
This study presents the interpretation of radio echo-sounding (RES) data collected during the 2003 geophysical campaign of PNRA (Italian National Research Project in Antarctica), which focused on the exploration of the Concordia Trench-Lake system in East Antarctica. The data allow us to identify a new lake (ITL-28) at the southern edge of the Concordia Trench and a series of N\u2013S trending subglacial troughs cutting through the Belgica Highlands. We have mapped the bedrock morphology at 3 km resolution, which led to an improved geographical and geomorphological characterization of the Concordia Trench, Concordia Ridge, Concordia Lake and South Hills. Improved knowledge of the Concordia Trench allowed us to model the 3-D geometry of the Concordia fault, suggesting that it played a role in governing the morpho-tectonic evolution of the bedrock in the Dome C region, and to propose a Cenozoic age for its activity. We recognize the importance of catchment basin morphology in hosting subglacial lakes, and discuss the role played by tectonics, glacial scouring and volcanism in the origin of the trench lakes, basin lakes and relief lakes, respectively