scholarly journals A detailed radiostratigraphic data set for the central East Antarctic Plateau spanning the last half million years

2020 ◽  
Author(s):  
Marie G. P. Cavitte ◽  
Duncan A. Young ◽  
Robert Mulvaney ◽  
Catherine Ritz ◽  
Jamin S. Greenbaum ◽  
...  
Keyword(s):  
Data Center ◽  
Ice Core ◽  
Radar Data ◽  
Glacial Cycles ◽  
Data Set ◽  
Ice Flow ◽  
Antarctic Plateau ◽  
The Past ◽  
Program Data ◽  
The U.S

Abstract. We present an ice-penetrating radar data set which consists of 26 internal reflecting horizons (IRHs) that cover the entire Dome C area of the East Antarctic plateau, the most extensive to date in the region. This data set uses radar surveys collected over the space of 10 years, starting with an airborne international collaboration in 2008 to explore the region, up to the detailed ground based surveys in support of the Beyond EPICA – Oldest Ice (BE-OI) European Consortium. Through direct correlation with the EPICA-DC ice core, we date 19 IRHs that span the past four glacial cycles, from the beginning of the Holocene to over 350 ka. We indirectly date and provide stratigraphic information for seven older IRHs using an 1-D ice flow inverse model, going back to an estimated 700 ka. Depth and age uncertainties are quantified for all IRHs and provided as part of the data set. The IRH data set presented in this study is available at the U.S. Antarctic Program Data Center (USAP-DC) (https://doi.org/10.15784/601411, Cavitte et al., 2020) and represents a contribution to the SCAR AntArchitecture program.

scholarly journals A detailed radiostratigraphic data set for the central East Antarctic Plateau spanning from the Holocene to the mid-Pleistocene

2021 ◽  
Vol 13 (10) ◽  
pp. 4759-4777
Author(s):  
Marie G. P. Cavitte ◽  
Duncan A. Young ◽  
Robert Mulvaney ◽  
Catherine Ritz ◽  
Jamin S. Greenbaum ◽  
...  
Keyword(s):  
Ice Core ◽  
Radar Data ◽  
Glacial Cycles ◽  
Data Set ◽  
Ice Flow ◽  
The Holocene ◽  
Antarctic Plateau ◽  
The Us ◽  
Core Site ◽  
Program Data

Abstract. We present an ice-penetrating radar data set which consists of 26 internal reflecting horizons (IRHs) that cover the entire Dome C area of the East Antarctic plateau, the most extensive to date in the region. This data set uses radar surveys collected over the space of 10 years, starting with an airborne international collaboration in 2008 to explore the region, up to the detailed ground-based surveys in support of the Beyond EPICA – Oldest Ice (BE-OI) European Consortium. Through direct correlation with the EPICA-DC ice core, we date 19 IRHs that span the past four glacial cycles, from 10 ka, beginning of the Holocene, to over 350 ka, ranging from 10 % to 83 % of the ice thickness at the EPICA-DC ice core site. We indirectly date and provide stratigraphic information for seven older IRHs using a 1D ice flow inverse model, going back to an estimated 700 ka. Depth and age uncertainties are quantified for all IRHs and provided as part of the data set. The IRH data set presented in this study is available at the US Antarctic Program Data Center (USAP-DC) (https://doi.org/10.15784/601411, Cavitte et al., 2020) and represents a contribution to the SCAR AntArchitecture action group (AntArchitecture, 2017).

scholarly journals Brief Communication: New radar constraints support presence of ice older than 1.5 Ma at Little Dome C

2020 ◽  
Author(s):  
David A. Lilien ◽  
Daniel Steinhage ◽  
Drew Taylor ◽  
Frédéric Parrenin ◽  
Catherine Ritz ◽  
...  
Keyword(s):  
Flow Model ◽  
Ice Core ◽  
Austral Summer ◽  
Basal Region ◽  
Glacial Cycles ◽  
Ice Flow ◽  
Vhf Radar ◽  
New Instrument ◽  
Drill Site ◽  
Ice Core Record

Abstract. The area near Dome C, East Antarctica, is thought to be one of the most promising targets for recovering a continuous ice-core record spanning more than a million years. The European Beyond EPICA consortium has selected Little Dome C, an area ~35 km south-east of Concordia Station, to attempt to recover such a record. Here, we present the results of the final ice-penetrating radar survey used to refine the exact drill site. These data were acquired during the 2019–2020 Austral summer using a new, multi-channel high-resolution VHF radar operating in the frequency range of 170–230 MHz. This new instrument is able to detect reflections in the near-basal region, where previous surveys were unable to trace continuous horizons. The radar stratigraphy is used to transfer the timescale of the EPICA Dome C ice core (EDC) to the area of Little Dome C, using radar isochrones dating back past 600 ka. We use these data to derive the expected depth–age relationship through the ice column at the now-chosen drill site, termed BELDC. These new data indicate that the ice at BELDC is considerably older than that at EDC at the same depth, and that there is about 375 m of ice older than 600 ka at BELDC. Stratigraphy is well preserved to 2565 m, below which there is a basal unit with unknown properties. A simple ice flow model tuned to the isochrones suggests ages likely reach 1.5 Ma near 2525 m, ~40 m above the basal unit and ~240 m above the bed, with sufficient resolution (14±1 ka m−1) to resolve 41 ka glacial cycles.

scholarly journals Characterizing the glaciological conditions at Halvfarryggen ice dome, Dronning Maud Land, Antarctica

2013 ◽  
Vol 59 (213) ◽  
pp. 9-20 ◽  
Author(s):  
Reinhard Drews ◽  
Carlos Martín ◽  
Daniel Steinhage ◽  
Olaf Eisen
Keyword(s):  
Flow Model ◽  
Ice Core ◽  
Ice Cores ◽  
Radar Data ◽  
Ice Thickness ◽  
Atmospheric Conditions ◽  
Ice Flow ◽  
International Partnerships ◽  
Drill Site ◽  
Dronning Maud Land

AbstractWe present a comprehensive approach (including field data, remote sensing and an anisotropic ice-flow model) to characterize Halvfarryggen ice dome in coastal Dronning Maud Land, Antarctica. This is a potential drill site for the International Partnerships in Ice Core Sciences, which has identified the need for ice cores covering atmospheric conditions during the last few millennia. We derive the surface topography, the ice stratigraphy from radar data, and accumulation rates which vary from 400 to 1670 kg m−2 a−1 due to preferred wind directions and changing surface slope. The stratigraphy shows anticlines and synclines beneath the divides. We transfer Dansgaard–Johnsen age–depth scales from the flanks along isochrones to the divide in the upper 20–50% of the ice thickness and show that they compare well with the results of a full-Stokes, anisotropic ice-flow model which predicts (1) 11 ka BP ice at 90% of the ice thickness, (2) a temporally stable divide for at least 2700–4500 years, (3) basal temperatures below the melting point (−12°C to −5°C) and (4) a highly developed crystal orientation fabric (COF). We suggest drilling into the apices of the deep anticlines, providing a good compromise between record length and temporal resolution and also facilitating studies of the interplay of anisotropic COF and ice flow.

scholarly journals Change of the ice rheology with climatic transitions – implication on ice flow modelling and dating of the EPICA Dome C core

2006 ◽  
Vol 2 (6) ◽  
pp. 1187-1219 ◽  
Author(s):  
G. Durand ◽  
F. Gillet-Chaulet ◽  
A. Svensson ◽  
O. Gagliardini ◽  
S. Kipfstuhl ◽  
...  
Keyword(s):  
Flow Model ◽  
Ice Core ◽  
Ice Sheets ◽  
Ice Cores ◽  
Horizontal Shear ◽  
Ice Flow ◽  
Flow Modelling ◽  
The Past ◽  
Ice Flows ◽  
Crystallographic Orientations

Abstract. The study of the distribution of the crystallographic orientations (the fabric) along ice cores supplies information on the past and current ice flows of ice-sheets. Beside the usually observed formation of a vertical single maximum fabric, the EPICA Dome Concordia ice core (EDC) shows an abrupt and unexpected strenghtening of its fabric during termination II around 1750 m depth. Such strengthenings were already observed for sites located on an ice-sheet. This suggests that horizontal shear could occur along the EDC core. Moreover, the change in the fabric leads to a modification of the viscosity between neighbouring ice layers. Through the use of an anisotropic ice flow model, we quantify the change in viscosity and investigate its implication on ice flow and dating.

scholarly journals Ice Flow Along an I.A.G.P. Flow Line and Interpretation of Data From an Ice Core in Terre Adélie, Antarctica

1979 ◽  
Vol 24 (90) ◽  
pp. 103-115 ◽  
Author(s):  
D. Raynaud ◽  
C. Lorius ◽  
W. F. Budd ◽  
N. W. Young
Keyword(s):  
Flow Line ◽  
Ice Core ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Gas Content ◽  
Ice Flow ◽  
The Core ◽  
The Past ◽  
Terre Adélie ◽  
Inland Ice

AbstractAn ice core has been obtained to the bedrock about 300 m deep in Terre Adélie, 5 km inland from the coast. Stable isotopes and gas content have been measured over the length of the core. The results have been interpreted in terms of the temperature and elevation of origin of the ice further inland on the ice sheet from the data obtained along an 800 km traverse towards Dome “C”, and from Dome “C”, at an elevation of about 3 200 m. The flow of the ice from Dome “C“ to the coast has been modelled to determine the ages and particle trajectories of the ice for present conditions.It has been found that the upper isotope and gas-content values in the core can be matched with the present regime using a base for ice flow above the present bed which is suggested by moraine in the ice core. The ice in the layer from the 200 m depth, where the age is apparently more than 5 000 years, to the 250 m depth, appears to have originated from conditions which differ substantially from those existing on the present inland ice-sheet surface. The results give an indication of a colder climate and greater ice-sheet thickness in the past.

scholarly journals On the occurrence of annual layers in Dome Fuji ice core early Holocene ice

2015 ◽  
Vol 11 (9) ◽  
pp. 1127-1137 ◽  
Author(s):  
A. Svensson ◽  
S. Fujita ◽  
M. Bigler ◽  
M. Braun ◽  
R. Dallmayr ◽  
...  
Keyword(s):  
Ice Core ◽  
Flow Analysis ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Early Holocene ◽  
High Temporal Resolution ◽  
High Accumulation ◽  
Data Set ◽  
Antarctic Plateau ◽  
Annual Layer

Abstract. Whereas ice cores from high-accumulation sites in coastal Antarctica clearly demonstrate annual layering, it is debated whether a seasonal signal is also preserved in ice cores from lower-accumulation sites further inland and particularly on the East Antarctic Plateau. In this study, we examine 5 m of early Holocene ice from the Dome Fuji (DF) ice core at a high temporal resolution by continuous flow analysis. The ice was continuously analysed for concentrations of dust, sodium, ammonium, liquid conductivity, and water isotopic composition. Furthermore, a dielectric profiling was performed on the solid ice. In most of the analysed ice, the multi-parameter impurity data set appears to resolve the seasonal variability although the identification of annual layers is not always unambiguous. The study thus provides information on the snow accumulation process in central East Antarctica. A layer counting based on the same principles as those previously applied to the NGRIP (North Greenland Ice core Project) and the Antarctic EPICA (European Project for Ice Coring in Antarctica) Dronning Maud Land (EDML) ice cores leads to a mean annual layer thickness for the DF ice of 3.0 ± 0.3 cm that compares well to existing estimates. The measured DF section is linked to the EDML ice core through a characteristic pattern of three significant acidity peaks that are present in both cores. The corresponding section of the EDML ice core has recently been dated by annual layer counting and the number of years identified independently in the two cores agree within error estimates. We therefore conclude that, to first order, the annual signal is preserved in this section of the DF core. This case study demonstrates the feasibility of determining annually deposited strata on the central East Antarctic Plateau. It also opens the possibility of resolving annual layers in the Eemian section of Antarctic ice cores where the accumulation is estimated to have been greater than in the Holocene.

scholarly journals A Vital Resource Supporting Antarctic Research

Eos ◽  
2021 ◽  
Vol 102 ◽  
Author(s):  
Suzanne Carbotte ◽  
Frank Nitsche ◽  
Allen Pope ◽  
Neville Shane ◽  
Kirsty Tinto
Keyword(s):  
Data Center ◽  
Valuable Data ◽  
Wide Range ◽  
Antarctic Research ◽  
Program Data ◽  
Vital Resource ◽  
The U.S

The U.S. Antarctic Program Data Center is providing new services to help scientists document, preserve, and disseminate their research and to facilitate reusability of a wide range of valuable data.

scholarly journals Brief communication: New radar constraints support presence of ice older than 1.5 Myr at Little Dome C

2021 ◽  
Vol 15 (4) ◽  
pp. 1881-1888
Author(s):  
David A. Lilien ◽  
Daniel Steinhage ◽  
Drew Taylor ◽  
Frédéric Parrenin ◽  
Catherine Ritz ◽  
...  
Keyword(s):  
Ice Core ◽  
Austral Summer ◽  
Basal Region ◽  
Glacial Cycles ◽  
Very High Frequency ◽  
Ice Flow ◽  
Vhf Radar ◽  
New Instrument ◽  
Drill Site ◽  
Ice Core Record

Abstract. The area near Dome C, East Antarctica, is thought to be one of the most promising targets for recovering a continuous ice-core record spanning more than a million years. The European Beyond EPICA consortium has selected Little Dome C (LDC), an area ∼ 35 km southeast of Concordia Station, to attempt to recover such a record. Here, we present the results of the final ice-penetrating radar survey used to refine the exact drill site. These data were acquired during the 2019–2020 austral summer using a new, multi-channel high-resolution very high frequency (VHF) radar operating in the frequency range of 170–230 MHz. This new instrument is able to detect reflectors in the near-basal region, where previous surveys were largely unable to detect horizons. The radar stratigraphy is used to transfer the timescale of the EPICA Dome C ice core (EDC) to the area of Little Dome C, using radar isochrones dating back past 600 ka. We use these data to derive the expected depth–age relationship through the ice column at the now-chosen drill site, termed BELDC (Beyond EPICA LDC). These new data indicate that the ice at BELDC is considerably older than that at EDC at the same depth and that there is about 375 m of ice older than 600 kyr at BELDC. Stratigraphy is well preserved to 2565 m, ∼ 93 % of the ice thickness, below which there is a basal unit with unknown properties. An ice-flow model tuned to the isochrones suggests ages likely reach 1.5 Myr near 2500 m, ∼ 65 m above the basal unit and ∼ 265 m above the bed, with sufficient resolution (19 ± 2 kyr m−1) to resolve 41 kyr glacial cycles.

scholarly journals Seismic wave propagation in anisotropic ice – Part 2: Effects of crystal anisotropy in geophysical data

2015 ◽  
Vol 9 (1) ◽  
pp. 385-398 ◽  
Author(s):  
A. Diez ◽  
O. Eisen ◽  
C. Hofstede ◽  
A. Lambrecht ◽  
C. Mayer ◽  
...  
Keyword(s):  
Seismic Waves ◽  
Ice Core ◽  
Radar Data ◽  
Seismic Wave Propagation ◽  
Elasticity Tensor ◽  
Seismic Velocities ◽  
Data Set ◽  
Ice Dynamics ◽  
Crystal Anisotropy ◽  
Abrupt Changes

Abstract. We investigate the propagation of seismic waves in anisotropic ice. Two effects are important: (i) sudden changes in crystal orientation fabric (COF) lead to englacial reflections; (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded travel times. Velocities calculated from the polycrystal elasticity tensor derived for the anisotropic fabric from measured COF eigenvalues of the EDML ice core, Antarctica, show good agreement with the velocity trend determined from vertical seismic profiling. The agreement of the absolute velocity values, however, depends on the choice of the monocrystal elasticity tensor used for the calculation of the polycrystal properties. We make use of abrupt changes in COF as a common reflection mechanism for seismic and radar data below the firn–ice transition to determine COF-induced reflections in either data set by joint comparison with ice-core data. Our results highlight the possibility to complement regional radar surveys with local, surface-based seismic experiments to separate isochrones in radar data from other mechanisms. This is important for the reconnaissance of future ice-core drill sites, where accurate isochrone (i.e. non-COF) layer integrity allows for synchronization with other cores, as well as studies of ice dynamics considering non-homogeneous ice viscosity from preferred crystal orientations.

scholarly journals Airborne ultra-wideband radar sounding over the shear margins and along flow lines at the onset region of the Northeast Greenland Ice Stream

2021 ◽  
Author(s):  
Steven Franke ◽  
Daniela Jansen ◽  
Tobias Binder ◽  
John D. Paden ◽  
Nils Dörr ◽  
...  
Keyword(s):  
High Resolution ◽  
Ice Core ◽  
Radar Data ◽  
Ultra Wideband ◽  
Flow Lines ◽  
Data Set ◽  
Ice Surface ◽  
Ice Stream ◽  
Spatial Coverage ◽  
Wideband Radar

Abstract. We present a high-resolution airborne radar data set (EGRIP-NOR-2018) for the onset region of the Northeast Greenland Ice Stream (NEGIS). The radar data were acquired in May 2018 with Alfred Wegener Institute’s multichannel ultra-wideband (UWB) radar mounted on the Polar6 aircraft. Radar profiles cover an area of ~24000 km2 and extend over the well-defined shear margins of the NEGIS. The survey area is centred at the location of the drill site of the East Greenland Ice-Core Project (EastGRIP) and several radar lines intersect at this location. The survey layout was designed to: (i) map the stratigraphic signature of the shear margins with radar profiles aligned perpendicular to ice flow, (ii) trace the radar stratigraphy along several flow lines and (iii) provide spatial coverage of ice thickness and basal properties. While we are able to resolve radar reflections in the deep stratigraphy, we can not fully resolve the steeply inclined reflections at the tightly folded shear margins in the lower part of the ice column. The NEGIS is causing the most significant discrepancies between numerically modelled and observed ice surface velocities. Given the high likelihood of future climate and ocean warming, this extensive data set of new high-resolution radar data in combination with the EastGRIP ice core will be a key contribution to understand the past and future dynamics of the NEGIS. The EGRIP-NOR-2018 radar data products can be obtained at the PANGAEA Data Publisher (https://doi.pangaea.de/10.1594/PANGAEA.928569; Franke et al. 2021a).

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