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  • 1
    Article
    Article
    Schmelzen die Polkappen? : wenn sich das Eis der Antarktis und Grönlands infolge der globalen Erwärmung in Wasser verwandelt, kommt es zu weltweiten Überflutungen (2001)
    Associated volumes
    Details Availability
    In: Spektrum der Wissenschaft, Heidelberg : Spektrum-der-Wiss.-Verl.-Ges., 1978, (2001), 11, Seite 30-37, 0170-2971
    In: year:2001
    In: number:11
    In: pages:30-37
    Type of Medium: Article
    Pages: zahlr. Ill
    ISSN: 0170-2971
    Language: German
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  • 2
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    High-resolution boundary conditions of an old ice target near Dome C, Antarctica (2018)
    Details
    Publication Date: 2020-10-13
    Description: A high-resolution (1 km line spacing) aerogeophysical survey was conducted over a region near the East Antarctic Ice Sheet’s Dome C that may hold a 1.5 Myr climate record. We combined new ice thickness data derived from an airborne coherent radar sounder with unpublished data that was in part unavailable for earlier compilations, and we were able to remove older data with high positional uncertainties. We generated a revised high-resolution digital elevation model (DEM) to investigate the potential for an old ice record in this region, and used laser altimetry to confirm a Cryosat-2 derived DEM for inferring the glaciological state of the candidate area. By measuring the specularity content of the bed, we were able to find an additional 50 subglacial lakes near the candidate site, and by Doppler focusing the radar data, we were able to map out the roughness of the bed at length scales of hundreds of meters. We find that the primary candidate region contains elevated rough topography interspersed with scattered subglacial lakes and some regions of smoother bed. Free subglacial water appears to be restricted from bed overlain by ice thicknesses of less than 3000 m. A site near the ice divide was selected for further investigation. The high resolution of this ice thickness data set also allows us to explore the nature of ice thickness uncertainties in the context of radar geometry and processing.
    Description: Published
    Description: 1897-1911
    Description: 5A. Paleoclima e ricerche polari
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    Geothermal flux and basal melt rate in the Dome C region inferred from radar reflectivity and heat modelling (2018)
    Details
    Publication Date: 2020-10-13
    Description: Basal melt rate is the most important physical quantity to be evaluated when looking for an old-ice drilling site, and it depends to a great extent on the geothermal flux (GF), which is poorly known under the East Antarctic ice sheet. Given that wet bedrock has higher reflectivity than dry bedrock, the wetness of the ice–bed interface can be assessed using radar echoes from the bedrock. But, since basal conditions depend on heat transfer forced by climate but lagged by the thick ice, the basal ice may currently be frozen whereas in the past it was generally melting. For that reason, the risk of bias between present and past conditions has to be evaluated. The objective of this study is to assess which locations in the Dome C area could have been protected from basal melting at any time in the past, which requires evaluating GF. We used an inverse approach to retrieve GF from radar inferred distribution of wet and dry beds. A 1-D heat model is run over the last 800 ka to constrain the value of GF by assessing a critical ice thickness, i.e. the minimum ice thickness that would allow the present local distribution of basal melting. A regional map of the GF was then inferred over a 80 kmx130 km area, with a N–S gradient and with values ranging from 48 to 60mWm-2. The forward model was then emulated by a polynomial function to compute a timeaveraged value of the spatially variable basal melt rate over the region. Three main subregions appear to be free of basal melting, two because of a thin overlying ice and one, north of Dome C, because of a low GF.
    Description: Published
    Description: 2231–2246
    Description: 4A. Oceanografia e clima
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    High resolution boundary conditions of an old ice target near Dome C, Antarctica (2017)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3The Cryosphere, COPERNICUS GESELLSCHAFT MBH, 11, pp. 1897-1911
    Details
    Publication Date: 2017-10-17
    Description: A high-resolution (1 km line spacing) aerogeophysical survey was conducted over a region near the East Antarctic Ice Sheet's Dome C that may hold a 1.5 Myr climate record. We combined new ice thickness data derived from an airborne coherent radar sounder with unpublished data that was in part unavailable for earlier compilations, and we were able to remove older data with high positional uncertainties. We generated a revised high-resolution digital elevation model (DEM) to investigate the potential for an old ice record in this region, and used laser altimetry to confirm a Cryosat-2 derived DEM for inferring the glaciological state of the candidate area. By measuring the specularity content of the bed, we were able to find an additional 50 subglacial lakes near the candidate site, and by Doppler focusing the radar data, we were able to map out the roughness of the bed at length scales of hundreds of meters. We find that the primary candidate region contains elevated rough topography interspersed with scattered subglacial lakes and some regions of smoother bed. Free subglacial water appears to be restricted from bed overlain by ice thicknesses of less than 3000 m. A site near the ice divide was selected for further investigation. The high resolution of this ice thickness data set also allows us to explore the nature of ice thickness uncertainties in the context of radar geometry and processing.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , notRev
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  • 5
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    Polarimetric radar reveals the spatial distribution of ice fabric at domes and divides in East Antarctica (2022)
    In:  EPIC3The Cryosphere, 16(5), pp. 1719-1739, ISSN: 1994-0424
    Details
    Publication Date: 2022-05-18
    Description: Ice crystals are mechanically and dielectrically anisotropic. They progressively align under cumulative deformation, forming an ice-crystal-orientation fabric that, in turn, impacts ice deformation. However, almost all the observations of ice fabric are from ice core analysis, and its influence on the ice flow is unclear. Here, we present a non-linear inverse approach to process co- and cross-polarized phase-sensitive radar data. We estimate the continuous depth profile of georeferenced ice fabric orientation along with the reflection ratio and horizontal anisotropy of the ice column. Our method approximates the complete second-order orientation tensor and all the ice fabric eigenvalues. As a result, we infer the vertical ice fabric anisotropy, which is an essential factor to better understand ice deformation using anisotropic ice flow models. The approach is validated at two Antarctic ice core sites (EPICA (European Project for Ice Coring in Antarctica) Dome C and EPICA Dronning Maud Land) in contrasting flow regimes. Spatial variability in ice fabric characteristics in the dome-to-flank transition near Dome C is quantified with 20 more sites located along with a 36 km long cross-section. Local horizontal anisotropy increases under the dome summit and decreases away from the dome summit. We suggest that this is a consequence of the non-linear rheology of ice, also known as the Raymond effect. On larger spatial scales, horizontal anisotropy increases with increasing distance from the dome. At most of the sites, the main driver of ice fabric evolution is vertical compression, yet our data show that the horizontal distribution of the ice fabric is consistent with the present horizontal flow. This method uses polarimetric-radar data, which are suitable for profiling radar applications and are able to constrain ice fabric distribution on a spatial scale comparable to ice flow observations and models.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
    Format: application/pdf
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  • 6
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    Antarctic Geothermal Heat Flow: Future research directions (2020)
    Scientific Committee on Antarctic Research (SCAR)
    In:  EPIC3SCAR-SERCE White Paper, Scientific Committee on Antarctic Research (SCAR), 9 p.
    Details
    Publication Date: 2022-05-31
    Description: Antarctic geothermal heat flow (GHF) affects the ice sheet temperature, determining how it slides and internally deforms, as well as the rheological behaviour of the lithosphere. However, GHF remains poorly constrained, with few borehole-derived estimates, and there are large discrepancies in currently available glaciological and geophysical estimates. This SCAR White Paper details current methods, discusses their challenges and limitations, and recommends key future directions in GHF research. We highlight the timely need for a more multidisciplinary and internationally-coordinated approach to tackle this complex problem.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Other , notRev
    Format: application/pdf
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  • 7
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    Stagnant ice and age modelling in the Dome C region, Antarctica (2023)
    Copernicus Publications
    In:  EPIC3The Cryosphere, Copernicus Publications, 17(8), pp. 3461-3483, ISSN: 1994-0416
    Details
    Publication Date: 2023-10-19
    Description: The European Beyond EPICA project aims to extract a continuous ice core of up to 1.5 Ma, with a maximum age density of 20 kyr m-1 at Little Dome C (LDC). We present a 1D numerical model which calculates the age of the ice around Dome C. The model inverts for basal conditions and accounts either for melting or for a layer of stagnant ice above the bedrock. It is constrained by internal reflecting horizons traced in radargrams and dated using the EPICA Dome C (EDC) ice core age profile. We used three different radar datasets ranging from a 10 000 km2 airborne survey down to 5 km long ground-based radar transects over LDC. We find that stagnant ice exists in many places, including above the LDC relief where the new Beyond EPICA drill site (BELDC) is located. The modelled thickness of this layer of stagnant ice roughly corresponds to the thickness of the basal unit observed in one of the radar surveys and in the autonomous phase-sensitive radio-echo sounder (ApRES) dataset. At BELDC, the modelled stagnant ice thickness is 198±44 m and the modelled oldest age of ice is 1.45±0.16 Ma at a depth of 2494±30 m. This is very similar to all sites situated on the LDC relief, including that of the Million Year Ice Core project being conducted by the Australian Antarctic Division. The model was also applied to radar data in the area 10-15 km north of EDC (North Patch), where we find either a thin layer of stagnant ice (generally 〈60 m) or a negligible melt rate (〈0.1 mm yr-1). The modelled maximum age at North Patch is over 2 Ma in most places, with ice at 1.5 Ma having a resolution of 9-12 kyr m-1, making it an exciting prospect for a future Oldest Ice drill site.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 8
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    Brief communication: New radar constraints support presence of ice older than 1.5 Myr at Little Dome C (2021)
    Copernicus Publications
    In:  EPIC3The Cryosphere, Copernicus Publications, 15(4), pp. 1881-1888, ISSN: 1994-0416
    Details
    Publication Date: 2024-03-14
    Description: 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 highresolution 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 375m 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, ∼65m above the basal unit and ∼265m above the bed, with sufficient resolution (19±2 kyrm-1) to resolve 41 kyr glacial cycles.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 9
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    Enhancement factors for grounded ice and ice shelves inferred from an anisotropic ice-flow model (2011)
    Cambridge University Press
    Details
    Publication Date: 2011-02-01
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of The International Glaciological Society (IGS).
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  • 10
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    Basal age, surface accumulation, basal melting, geothermal flux and Lliboutry exponent of the velocity profile in the Dome C area (2017)
    PANGAEA
    In:  Supplement to: Parrenin, Frédéric; Cavitte, Marie G P; Blankenship, Donald D; Chappellaz, Jérôme A; Fischer, Hubertus; Gagliardini, Olivier; Masson-Delmotte, Valerie; Passalacqua, Olivier; Ritz, Catherine; Roberts, Jason L; Siegert, Martin J; Young, Duncan A (2017): Is there 1.5-million-year-old ice near Dome C, Antarctica? The Cryosphere, 11(6), 2427-2437, https://doi.org/10.5194/tc-11-2427-2017
    Details
    Publication Date: 2023-03-31
    Description: Ice sheets provide exceptional archives of past changes in polar climate, regional environment and global atmospheric composition. The oldest dated deep ice core drilled in Antarctica has been retrieved at EPICA Dome C (EDC), reaching ~800,000 years. Obtaining an older paleoclimatic record from Antarctica is one of the greatest challenges of the ice core community. Here, we use internal isochrones, identified from airborne radar coupled to ice-flow modelling to estimate the age of basal ice along transects in the Dome C area. Three glaciological properties are inverted from isochrones: surface accumulation rate; geothermal flux; and the exponent of the Lliboutry velocity profile. We find that old ice (〉1 Myr, 1 million years) likely exists in two regions: one ~40 km south-west of Dome C along the ice divide to Vostok, close to a secondary dome that we name "Little Dome C" (LDC); and a second region named "North Patch" (NP) located 10-30 km north-east of Dome C, in a region where the geothermal flux is apparently relatively low. Our work demonstrates the value of combining radar observations with ice flow modelling to accurately represent the true nature of ice flow, and the formation of ice-sheet architecture, in the centre of large ice sheets.
    Keywords: Accumulation rate, standard deviation; Accumulation rate in ice equivalent per year; AGE; Antarctica; Distance; DomeC_area; Factor; Ground heat, flux; Ground heat, flux, standard deviation; Height; Ice thickness; LATITUDE; LONGITUDE; Melt rate; Melt rate, standard deviation; MULT; Multiple investigations; Number of years; Standard deviation
    Type: Dataset
    Format: text/tab-separated-values, 95189 data points
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