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Browsing Book Chapters by Subject "Antarctica"

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    10Be concentrations in snow at Law Dome, Antarctica following the 29 October 20 and 20 January 2005 solar cosmic ray events
    (World Scientific, 2009-08) Pedro, JB; Smith, AM; Duldig, ML; Klekociuk, AR; Simon, KJ; Curran, MAJ; van Ommen, TD; Fink, D; Morgan, VI; Galton-Fenzi, BK
    Recent model calculations have attempted to quantify the contribution of major energetic solar cosmic ray (SCR) events to 10Be production.1,2 In this study we compare modeled 10Be production by SCR events to measured 10Be concentrations in a Law Dome snow pit record. The snow pit record spans 2.7 years, providing a quasi-monthly 10Be sampling resolution which overlaps with the SCR events of 29 Oct 2003 and 20 Jan 2005. These events were calculated to increase monthly 10Be production in the polar atmosphere (>65° S geomagnetic latitude) by ~60% and ~120% above the GCR background, respectively2. A strong peak in 10Be concentrations (>4σ above the 2.7 y mean value) was observed ~1 month after the 20 Jan 2005 event. By contrast, no signal in 10Be concentrations was observed following the weaker 29 Oct 2003 series of events. The concentration of 10Be in ice core records involves interplay between production, transport, and deposition processes. We used a particle dispersion model to assess vertical and meridional transport of aerosols from the lower stratosphere where SCR production of 10Be is expected to occur, to the troposphere from where deposition to the ice sheet occurs. Model results suggested that a coherent SCR production signal could be transported to the troposphere within weeks to months following both SCR events. We argue that only the 20 Jan 2005 SCR event was observed in measured concentrations due to favorable atmospheric transport, relatively high production yield compared to the 29 Oct 2003 event, and a relatively high level of precipitation in the Law Dome region in the month following the event. This result encourages further examination of SCR signals in 10Be ice core data. © 2009 World Scientific Publishing
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    Ellsworth Subglacial Lake, West Antarctica: a review of its history and recent field campaigns
    (John Wiley & Sons, Inc, 2011-01-01) Ross, N; Siegert, MJ; Rivera, A; Bentley, MJ; Blake, D; Capper, L; Clarke, R; Cockell, CS; Corr, HFJ; Harris, W; Hill, C; Hindmarsh, RCA; Hodgson, DA; King, EC; Lamb, H; Maher, B; Makinson, K; Mowlem, M; Parnell, J; Pearce, DA; Priscu, J; Smith, AM; Tait, A; Tranter, M; Wadham, JL; Whalley, WB; Woodward, JC
    Ellsworth Subglacial Lake, first observed in airborne radio echo sounding data acquired in 1978, is located within a long, deep subglacial trough within the Ellsworth Subglacial Highlands of West Antarctica. Geophysical surveys have characterized the lake, its subglacial catchment, and the thickness, structure, and flow of the overlying ice sheet. Covering 28.9 km2 , Ellsworth Subglacial Lake is located below 2.9 to 3.3 km of ice at depths of -1361 to -1030 m. Seismic reflection data have shown the lake to be up to 156 m deep and underlain by unconsolidated sediments. Ice sheet flow over the lake is characterized by low velocities (<6 m yr-1 ), flow convergence, and longitudinal extension. The lake appears to be in steady state, although the hydrological balance may vary over glacial-interglacial cycles. Direct access, measurement, and sampling of Ellsworth Subglacial Lake are planned for the 2012/2013 Antarctic field season. The aims of this access experiment are to determine (1) the presence, character, and maintenance of microbial life in Antarctic subglacial lakes and (2) the Quaternary history of the West Antarctic ice sheet. Geophysical data have been used to define a preferred lake access site. The factors that make this location suitable for exploration are (1) a relatively thin overlying ice column (~3.1 km), (2) a significant measured water depth (~143 m), (3) >2 m of sediment below the lake floor, (4) water circulation modeling suggesting a melting ice-water interface, and (5) coring that can target the deepest point of the lake floor away from marginal, localized sediment sources. © 2011 American Geophysical Union.
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    Modern to Glacial Age subglacial meltwater drainage at Law Dome, coastal East Antarctica from topography, sediments and jökulhlaup observations
    (The Geological Society of London, 2017-07-12) Goodwin, ID; Roberts, JL; Etheridge, DM; Hellstrom, JC; Moy, AD; Ribo, M; Smith, AM
    Rare jökulhlaup events, also known as subglacial lake outburst flood events, have been observed at the Law Dome ice margin and provide an insight into the physical characteristics of subglacial meltwater and drainage. The subglacial topography based on data from the BEDMAP2 and ICECAP projects, together with subsurface transects of the ice margin obtained using ground-penetrating radar, reveal several lakes and lake-like depressions and the drainage pathways of two jökulhlaup events. Oxygen isotope typing of the meltwater during the most recent (2014) jökulhlaup event, combined with ice margin stratigraphy, enable the identification of ice tunnel melt pathways that exploit the 30–90° dipping basal ice layering. The presence of subglacial meltwater beneath Law Dome during the Holocene to Glacial periods is confirmed by the dendritic drainage pattern in the subglacial morphology and extensive layers of basal regelation ice and subglacial carbonate precipitate deposits found within the Løken Moraines sediments. These subglacial carbonates, including ooid layers, formed from the mixing of glacial meltwater and seawater at 72 ka BP. The combined evidence indicates that the ocean discharge of subglacial meltwater may be variable and/or is periodically blocked by basal freezing events near the ice sheet terminus. © 2018 The Author(s). Published by The Geological Society of London.