HR: 12:05h
AN: C12C-08 INVITED     [Abstracts]
TI: A New Hot Water Drill for Glaciological, Geochemical and Biological Studies of the Subglacial Lakes Beneath the Vatnaj”kull Ice Cap, Iceland
AU: * Thorsteinsson, T
EM: thor@os.is
AF: National Energy Authority, Grensasvegi 9, Reykjavik, IS-108 Iceland
AU: Elefsen, S
EM: se@os.is
AF: National Energy Authority, Grensasvegi 9, Reykjavik, IS-108 Iceland
AU: Johannesson, T
EM: tj@vedur.is
AF: Icelandic Meteorological Office, Bustadavegi 9, Reykjavik, IS-150 Iceland
AU: Thorsteinsson, T
EM: throsturt@raunvis.hi.is
AF: University of Iceland, Sturlugata 7, Reykjavik, IS-101 Iceland
AB: The center of hot-spot volcanic activity in Iceland is located beneath the NW-part of Vatnaj”kull, giving rise to frequent and intense ice-volcano interactions. Five subglacial lakes are known to exist in regions of high geothermal and/or volcanic activity within this area [1], which is now attracting the interest of researchers studying the possible presence of microbial life in Lake Vostok and other subglacial lakes beneath the Antarctic ice sheet [2]. In addition, the lakes beneath Vatnaj”kull are increasingly being viewed as terrestrial analogs of water bodies beneath ice covers on planets and moons in the Solar System, e.g. Mars and Europa. The ice shelf covering the Gr¡msv”tn subglacial lake was penetrated with a hot water drill in June 2002, a few months after a j”kulhlaup that released most of the water from the lake. The ice thickness was 280 m and the water depth was 20 m at the drilling site. The lake water was found to be at the melting point, dominated by glacial melt and not mixed with hydrothermal fluids from the geothermal system. The microbial population found in samples from the lake water (2*10e4 cells/ml) and bottom sediment (4*10e7 cells/g) [3] may be derived from organisms transported with windborne dust particles from nearby deserts and deposited on the surface of the ice shelf. Studies of an ice core drilled to 115 m depth at the same site revealed an average dust concentration of 4 ppmv in the ice shelf, and the timescale for downward transport through the ice shelf is estimated to be 150-200 years. Basal melting of the ice shelf leads to dust deposition on the lake bottom at an estimated rate of 0.024 kg/m2/yr [4]. A new hot water drilling system capable of drilling through 600 m of ice has now been constructed for follow-up studies of the subglacial lakes in Iceland. In this system, glycol is heated in a combustion unit and then circulated in a closed loop system through a heat exchanger located within a 0.6 m3 snow melter. The meltwater is then heated to 95 °C in a high-pressure pump and passed through filters and a UV-sterilization unit prior to entering the hose and drill stem. The new system has been tested with success on the Langj”kull ice cap in June 2005, where the snow melting efficiency was found to be 500 liters/hr and the water consumption during maximum load was 480 liters/hr. The average drilling speed was 45 m/hr in the depth interval 0-100 m, in ice that did not contain any layers of volcanic tephra. The sterilization efficiency of the system is currently being investigated and it is hoped that the new system will be capable of drilling into subglacial lakes with a minimal risk of borehole contamination. Among the targets for future drillings are two hitherto unsampled water bodies, the Skaft rkatlar (Skaftar cauldrons), located beneath 550 m thick ice cover 10-15 km NW of Grimsv”tn. The cauldrons empty out in j”kulhlaups every 2 years on average, and existing data on the j”kulhlaup hydrographs and floodwater geochemistry make these subglacial water bodies prime candidates for future glaciological, geochemical and biological investigations. References: [1] H. Bj”rnsson (2002), Glob. Planet. Change 35, 255-271. [2] J.C. Priscu et al. (1999), Science, 286, 2141-2144. [3] E.J. Gaidos et al., Astrobiology, 4, 327-344. [4] Thorsteinsson et al. (2003), 3rd Mars Polar Conference, Alberta, Canada (Abstract # 8134).
DE: 0456 Life in extreme environments
DE: 0776 Glaciology (1621, 1827, 1863)
SC: Cryosphere [C]
MN: Fall Meeting 2005