Browsing by Author "Tulaczyk, Slawek"

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Antarctic subglacial water: Origin, evolution and ecology
(2008-09) Priscu, John C.; Tulaczyk, Slawek; Studinger, Michael; Kennicutt II, Mahlon C.; Christner, Brent C.; Foreman, Christine M.
Recent discoveries in the polar regions have revealed that subglacial environments provide a habitat for life in a setting that was previously thought to be inhospitable. These habitats consist of large lakes, intermittently flowing rivers, wetlands, and subglacial aquifers. This chapter presents an overview of the geophysical, chemical, and biological properties of selected subglacial environments. The focus is on the large subglacial systems lying beneath Antarctic ice sheets where most of the subglacial water on our planet is thought to exist. Specifically, this chapter addresses the following topics: (1) the distribution, origin, and hydrology of Antarctic subglacial lakes; (2) Antarctic ice streams as regions of dynamic liquid-water movement that influence ice-sheet dynamics; and (3) subglacial environments as habitats for life and reservoirs of organic carbon.
Subglacial Lake Whillans microbial biogeochemistry: a synthesis of current knowledge
(2016-01) Mikucki, Jill A.; Lee, P.A.; Ghosh, D.; Purcell, A.D.; Mitchell, Andrew C.; Mankoff, K.D.; Fisher, A.T.; Tulaczyk, Slawek; Carter, Sasha; Siegfried, Matthew R.; Fricker, H.A.; Hodson, Timothy; Coenen, J.; Powell, Ross; Scherer, Reed; Vick-Majors, Trista J.; Achberger, Amanda M.; Christner, Brent C.; Tranter, Martyn
Liquid water occurs below glaciers and ice sheets globally, enabling the existence of an array of aquatic microbial ecosystems. In Antarctica, large subglacial lakes are present beneath hundreds to thousands of metres of ice, and scientific interest in exploring these environments has escalated over the past decade. After years of planning, the first team of scientists and engineers cleanly accessed and retrieved pristine samples from a West Antarctic subglacial lake ecosystem in January 2013. This paper reviews the findings to date on Subglacial Lake Whillans and presents new supporting data on the carbon and energy metabolism of resident microbes. The analysis of water and sediments from the lake revealed a diverse microbial community composed of bacteria and archaea that are close relatives of species known to use reduced N, S or Fe and CH4 as energy sources. The water chemistry of Subglacial Lake Whillans was dominated by weathering products from silicate minerals with a minor influence from seawater. Contributions to water chemistry from microbial sulfide oxidation and carbonation reactions were supported by genomic data. Collectively, these results provide unequivocal evidence that subglacial environments in this region of West Antarctica host active microbial ecosystems that participate in subglacial biogeochemical cycling.
WISSARD at Subglacial Lake Whillans, West Antarctica: scientific operations and initial observations
(2014-09) Tulaczyk, Slawek; Mikucki, Jill A.; Siegfried, Matthew R.; Priscu, John C.; Barcheck, C. Grace; Beem, Lucas H.
A clean hot-water drill was used to gain access to Subglacial Lake Whillans (SLW) in late January 2013 as part of the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project. Over 3 days, we deployed an array of scientific tools through the SLW borehole: a downhole camera, a conductivity–temperature–depth (CTD) probe, a Niskin water sampler, an in situ filtration unit, three different sediment corers, a geothermal probe and a geophysical sensor string. Our observations confirm the existence of a subglacial water reservoir whose presence was previously inferred from satellite altimetry and surface geophysics. Subglacial water is about two orders of magnitude less saline than sea water (0.37–0.41 psu vs 35 psu) and two orders of magnitude more saline than pure drill meltwater (<0.002 psu). It reaches a minimum temperature of –0.55°C, consistent with depression of the freezing point by 7.019 MPa of water pressure. Subglacial water was turbid and remained turbid following filtration through 0.45 μm filters. The recovered sediment cores, which sampled down to 0.8 m below the lake bottom, contained a macroscopically structureless diamicton with shear strength between 2 and 6 kPa. Our main operational recommendation for future subglacial access through water-filled boreholes is to supply enough heat to the top of the borehole to keep it from freezing.