High-resolution subglacial topography around Dome Fuji, Antarctica, based on ground-based radar surveys over 30 years (original) (raw)
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Geological Society, London, Special Publications, 2017
Ice cores in Antarctica and Greenland reveal ice-crystal fabrics that can be softer under simple shear compared with isotropic ice. Owing to the sparseness of ice cores in regions away from the ice divide, we currently lack information about the spatial distribution of ice fabrics and its association with ice flow. Radio-wave reflections are influenced by ice-crystal alignments, allowing them to be tracked provided reflections are recorded simultaneously in orthogonal orientations (polarimetric measurements). Here, we image spatial variations in the thickness and extent of ice fabric across Dome A in East Antarctica, by interpreting polarimetric radar data. We identify four prominent fabric units, each several hundred metres thick, extending over hundreds of square kilometres. By tracing internal ice-sheet layering to the Vostok ice core, we are able to determine the approximate depth–age profile at Dome A. The fabric units correlate with glacial–interglacial cycles, most noticeably...
Annals of Glaciology, 2013
This study aims to demonstrate that deep ice cores can be synchronized using internal horizons in the ice between the drill sites revealed by airborne radio-echo sounding (RES) over a distance of >1000km, despite significant variations in glaciological parameters, such as accumulation rate between the sites. In 2002/03 a profile between the Kohnen station and Dome Fuji deep ice-core drill sites, Antarctica, was completed using airborne RES. The survey reveals several continuous internal horizons in the RES section over a length of 1217 km. The layers allow direct comparison of the deep ice cores drilled at the two stations. In particular, the counterpart of a visible layer observed in the Kohnen station (EDML) ice core at 1054 m depth has been identified in the Dome Fuji ice core at 575 m depth using internal RES horizons. Thus the two ice cores can be synchronized, i.e. the ice at 1560 m depth (at the bottom of the 2003 EDML drilling) is ∼49ka old according to the Dome Fuji age/...
Site information and initial results from deep ice drilling on Law Dome, Antarctica
Journal of Glaciology, 1997
The aim of deep ice drilling on Law Dome, Antarctica, has been to exploit the special characteristics of Law Dome summit, i.e. low temperature and high accumulation near an ice divide, to obtain a high-resolution ice core for climatic/environmental studies of the Holocene and the Last Glacial Maximum (LGM). Drilling was completed in February 1993, when basal ice containing small fragments of rock was reached at a depth of 1196 m. Accurate ice dating, obtained by counting annual layers revealed by fine-detail δ18О, peroxide and electrical-conductivity measurements, is continuous down to 399 m, corresponding to a date of AD 1304. Sulphate concentration measurements, made around depths where conductivity tracing indicates volcanic fallout, allow confirmation of the dating (for Agung in 1963 and Tambora in 1815) or estimates of the eruption date from the ice dating (for the Kuwae, Vanuatu, eruption ~1457). The lower part of the core is dated by extrapolating the layer-counting using a s...
The ANDRILL Initiative: Stratigraphic Drilling for Climatic and Tectonic History in Antarctica
2002
Limited exposures of Cenozoic strata in Antarctica (due to ice cover) and the low number of stratigraphic drillholes on the continental margin has forced geoscientists to interpret ice sheet history from information derived from lower latitude proxy records. Leading paradigms have been driven by the oxygen isotope record from deep-sea cores and eustatic changes inferred from sequence stratigraphic records on passive continental margins. Interpretations based on these proxy records have little direct confirmation from geologic records in Antarctica. Sedimentary archives that were recently recovered by the Cape Roberts Project (CRP) prove that high-quality proximal records of past ice sheet behavior are obtainable. The ANDRILL (ANtarctic DRILLing) Initiative is a consortium of five nations - Germany, Italy, New Zealand, United Kingdom and United States that proposes to drill a portfolio of sites in McMurdo Sound to recover new sections of Cenozoic strata from locations proximal to the ice sheet that are ideally suited to record and date ice sheet oscillations, and associated oceanic and climatic variations. Five themes with an overarching climate and glacial focus are the core of ANDRILL's scientific plan and include: 1) glacial transitions/steps and stages in the development of the Antarctic cryosphere, 2) periods of climatic warmth, 3) orbital and sub-orbital climatic variability, and the role of Antarctic ice cover on global sea-level and oceanic circulation, 4) origins and adaptations of polar biota, and 5) Antarctic Rift evolution and uplift of the Transantarctic Mountains. ANDRILL's McMurdo Sound Portfolio will achieve its scientific objectives through an integrated three-phase approach. The first phase comprises a geophysical survey program including gravity and magnetic surveys, and seismic acquisition from the sea-ice and ice shelf to document basin extent, architecture and to correlate drilling targets to existing drillcores. The second phase includes four seasons of drilling to obtain high-resolution, seismically-linked, chronologically well-constrained stratigraphic sections from the Antarctic margin to link proximal pre-glacial and interglacial-glacial records to proxy climate records from lower latitudes. The last phase will integrate newly acquired geological data into glaciological, climate and oceanographic models in order to determine global links and the past and future role of the Antarctic cryosphere in global environmental change. New drilling tools are currently being developed from proven technology that was employed during the CRP. The new ANDRILL drilling systems will have the potential for: 1) high percentage core recovery (> 97%), 2) recovery of strata from a sea-ice and ice shelf platform over water up to 1000 m deep, 3) a drilling rate 2-3 times faster than the CRP system, and 4) recovery of soft sediment.