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Probing Subglacial Environments Under the Whillans Ice Stream

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Probing Subglacial Environments Under the Whillans Ice Stream Eos, Vol. 91, No. 29, 20 July 2010 thermal and geotechnical probes, and Probing Subglacial Environments oceanographic moorings, some of which will remain as long- term observatories. Under the Whillans Ice Stream WISSARD Components PAGES 253–254 of the bed, constrain long- term history of WISSARD consists of three interrelated ice flow across the region, and provide subprojects. Lake and Ice Stream Water and wet sediments under ice sheets spatial context for interpretation of Subglacial Access Research Drilling can play an important role in regulating borehole findings. ( LISSARD) focuses on how active the rate of ice stream flow in Antarctica, Boreholes will be used to (1) collect subglacial lakes control temporal particularly over short time scales. Indeed, samples of subglacial water, sediments, variability of ice stream dynamics the discharge of subglacial lakes has been and basal ice for biological, geochemical, and mass balance. Robotic Access to linked to an increase in ice velocity of Byrd glaciological, sedimentological, and Grounding- zones for Exploration and Glacier by 10% for 14 months [Stearns et al., micropaleontological analyses; (2) measure Science ( RAGES) concentrates on stability 2008], and studies in West Antarctica have physical and chemical conditions of an of ice stream grounding zones, the shown that subglacial water can significantly ice shelf cavity and determine their spatial regions of the ice sheet where conditions influence overall ice stream dynamics variability; and (3) investigate sedimentary change from grounded ice sheet to freely [Fricker and Scambos, 2009], particularly at features and components, subglacial water floating ice shelf as the ice flows to the the seaward margin [Pollard and DeConto, discharge, oceanography, and basal ice sea. Typically several kilometers wide, 2009]. at the seaward side of the grounding zone the grounding zone may be perturbed The subglacial environment of Antarctica and within the cavity beneath the ice shelf. by increased thermal ocean forcing, also is an unexplored component of the Subglacial access and data collection internal ice stream dynamics, subglacial biosphere. Low temperatures, complete have required designing or customizing sediment flux to the grounding zone, and/ darkness, and direct isolation from the many instruments, including a submersible or filling or draining cycles of subglacial atmosphere for millions of years make this multisensor, a remotely operated vehicle lakes upstream. Finally, Geomicrobiology one of the most extreme environments for surveying under ice, sediment corers, of Antarctic Subglacial Environments on the planet [Priscu et al., 2008]. Additionally, microorganisms beneath the ice sheet may play an important role in mineral weathering of basement rock and sediments, making them likely contributors to geochemical inputs into the surrounding ocean. Despite the potential importance of subglacial environments, these areas have yet to be sampled in a comprehensive, integrated fashion. To address this issue, the Antarctic Integrated System Science program of the U.S. National Science Foundation’s (NSF) Office of Polar Programs has funded a 6- year integrative study of subglacial environments in West Antarctica, called the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project (http:// www . wissard .org). Begun in 2009, WISSARD will assess how water beneath a West Antarctic ice stream and beneath the Ross Ice Shelf influences complex glaciological, geological, microbiological, geochemical, hydrological, and oceanographic systems (see Figure 1). Scientific Goals The WISSARD project will integrate surface geophysical surveys with borehole and subglacial sampling to test the overarching hypothesis that active hydrological systems connect various subglacial environments and exert major control on ice sheet dynamics, geochemistry, and metabolic and Fig. 1. Map of the Whillans Ice Stream subglacial hydrologic system (modified from Fricker phylogenetic diversity within glacial and Scamos [2009]) with annotation of the predicted flow path (light gray) of subglacial environments. Exact selection of drill sites water from subglacial Lake Whillans to the grounding line (marked in black). Marked are the will be based on safety considerations geographical study areas for the Lake and Ice Stream Subglacial Access Research Drilling and accessibility as determined through ( LISSARD), Geomicrobiology of Antarctic Subglacial Environments ( GBASE), and Robotic Access radar, seismic, and satellite data. Surface to Grounding- zones for Exploration and Science ( RAGES) components of the project. The white geophysical surveys will also determine outlines indicate the locations of subglacial lakes. Inset map shows the location of Whillans Ice regional geologic and hydrologic structures Stream (black square) with respect to the Ross Ice Shelf and the Antarctic continent. Eos, Vol. 91, No. 29, 20 July 2010 ( GBASE) addresses microbial metabolic U.S. National Oceanic and Atmospheric Acknowledgments and phylogenetic diversity and associated Administration and the Gordon and Betty biogeochemical rock weathering and Moore Foundation. We thank the following principal elemental transformations in subglacial The current plan is to use an NSF- funded investigators and associates of WISSARD, lake and grounding zone environments. hot- water drill that can reach the subglacial whose ideas and data are presented in LISSARD and GBASE will target environment within a day of initiating a this brief report: S. Kelly, A. Mitchell, and subglacial Lake Whillans, a hydrologically borehole. Meltwater from the borehole will R. L. Edwards (Montana State University); active lake beneath the Whillans Ice be filtered through 0.5- and 0.2- micrometer S. Anandakrishnan and H. Horgan Stream (Figure 1). Through WISSARD’s filters and passed through an ultraviolet (Pennsylvania State University); B. C. drilling program, access to the lake sterilization system to reduce the number Christner (Louisiana State University); H. A. is scheduled for the 2012–2013 field of viable cells within the fluid. Bacterial Fricker and J. P. Severinghaus (Scripps season. The lake is part of an extensive numbers will be monitored in the borehole Institution of Oceanography); D. M. Holland hydrological system under the Mercer and water to ensure it remains below that in the (New York University); R. W. Jacobel Whillans ice streams that was discovered ice sheet. This process will ensure that the (St. Olaf College); J. A. Mikucki (Dartmouth through analysis of repeat track laser subglacial environment remains pristine College); and R. P. Scherer (Northern Illinois altimetry data from NASA’s Ice, Cloud, and and that samples will not be contaminated University). land Elevation Satellite ( ICESat) [Fricker by our drilling efforts. et al., 2007]. The discovery was based on Scientists intend to demonstrate a clean References the detection of ice surface deformation, sampling strategy by conducting two Fricker, H. A., and T. Scambos (2009), Connected presumed to be a response to subglacial intensive tests of this technology before subglacial lake activity on lower Mercer and water activity. In fact, surface expressions making any attempt at subglacial access Whillans ice streams, West Antarctica, 2003– of two complete fill and drain cycles of the drilling. The first test will occur in the 2008, J. Glaciol., 55(190), 303–315. lake between October 2003 and October United States in 2010, and the second will Fricker, H. A., T. Scambos, R. Bindschadler, and 2009 were observed, leading researchers occur during the 2011–2012 season on the L. Padman (2007), An active subglacial water sys- to estimate that water in the lake drains Ross Ice Shelf, which will more closely tem in West Antarctica mapped from space, Sci- and refills about every 3 years. approach conditions expected at the ence, 315(5818), 1544–1548, doi:10.1126/​­science During the 2007–2008 field season, ice- study site. This testing will demonstrate . 1136897. Pollard, D., and R. M. DeConto (2009), Modelling penetrating radar surveys showed that ice the efficacy of the filtration system, West Antarctic ice sheet growth and collapse thickness above subglacial Lake Whillans putting researchers in compliance with through the past five million years, Nature, 458, is only 700 meters and that the depth of the Protocol on Environmental Protection 329–332, doi:10.1038/nature07809. water in the lake is greater than 8 meters to the Antarctic Treaty, which states that Priscu, J. C., S. Tulaczyk, M. Studinger, M. C. Ken- even after lake drainage events. RAGES activities in the treaty area shall be planned nicutt II, B. C. Christner, and C. M. Foreman and GBASE will examine the Whillans Ice and conducted so as to limit adverse (2008), Antarctic subglacial water: Origin, evolu- Stream grounding zone site because of its impacts on the Antarctic environment and tion and ecology, in Polar Lakes and Rivers: Lim- hydropotential linkage with subglacial Lake dependent and associated ecosystems. nology of Arctic and Antarctic Aquatic Ecosystems, Whillans, and because a wedge of sediment edited by W. F. Vincent and J. Laybourn- Parry, pp. 119–135, Oxford Univ. Press, New York. has been detected in a zone behind the Toward a New Chapter in Polar Science Stearns, L. A., B. E. Smith, and G. S. Hamilton grounding line. This wedge could cause (2008), Increased flow speed on a large East Ant- water to pool, influencing ice flow. Sampling Following more than
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