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  • 1
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    Online Resource
    A representative density profile of the North Greenland snowpack
    Copernicus GmbH ; 2016
    In:  The Cryosphere Vol. 10, No. 5 ( 2016-09-07), p. 1991-2002
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 10, No. 5 ( 2016-09-07), p. 1991-2002
    Abstract: Abstract. Along a traverse through North Greenland in May 2015 we collected snow cores up to 2 m depth and analyzed their density and water isotopic composition. A new sampling technique and an adapted algorithm for comparing data sets from different sites and aligning stratigraphic features are presented. We find good agreement of the density layering in the snowpack over hundreds of kilometers, which allows the construction of a representative density profile. The results are supported by an empirical statistical density model, which is used to generate sets of random profiles and validate the applied methods. Furthermore we are able to calculate annual accumulation rates, align melt layers and observe isotopic temperatures in the area back to 2010. Distinct relations of δ18O with both accumulation rate and density are deduced. Inter alia the depths of the 2012 melt layers and high-resolution densities are provided for applications in remote sensing.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    DOI: 10.5194/tc-10-1991-2016
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2016
    detail.hit.zdb_id: 2393169-3
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  • 2
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    Relating regional and point measurements of accumulation in southwest Greenland
    Copernicus GmbH ; 2020
    In:  The Cryosphere Vol. 14, No. 1 ( 2020-01-31), p. 385-402
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 14, No. 1 ( 2020-01-31), p. 385-402
    Abstract: Abstract. In recent decades, the Greenland ice sheet (GrIS) has frequently experienced record melt events, which have significantly affected surface mass balance (SMB) and estimates thereof. SMB data are derived from remote sensing, regional climate models (RCMs), firn cores and automatic weather stations (AWSs). While remote sensing and RCMs cover regional scales with extents ranging from 1 to 10 km, AWS data and firn cores are point observations. To link regional scales with point measurements, we investigate the spatial variability of snow accumulation (bs) within areas of approximately 1–4 km2 and its temporal changes within 2 years of measurements. At three different sites on the southwestern GrIS (Swiss Camp, KAN-U, DYE-2), we performed extensive ground-penetrating radar (GPR) transects and recorded multiple snow pits. If the density is known and the snowpack dry, radar-measured two-way travel time can be converted to snow depth and bs. We spatially filtered GPR transect data to remove small-scale noise related to surface characteristics. The combined uncertainty of bs from density variations and spatial filtering of radar transects is at 7 %–8 % per regional scale of 1–4 km2. Snow accumulation from a randomly selected snow pit is very likely representative of the regional scale of 1–4 km2 (with probability p=0.8 for a value within 10 % of the regional mean for KAN-U, and p〉0.95 for Swiss Camp and DYE-2). However, to achieve such high representativeness of snow pits, it is required to determine the average snow depth within the vicinity of the pits. At DYE-2, the spatial pattern of snow accumulation was very similar for 2 consecutive years. Using target reflectors placed at respective end-of-summer-melt horizons, we additionally investigated the occurrences of lateral redistribution within one melt season. We found no evidence of lateral flow of meltwater in the current climate at DYE-2. Such studies of spatial representativeness and temporal changes in accumulation are necessary to assess uncertainties of the linkages of point measurements and regional-scale data, which are used for validation and calibration of remote-sensing data and RCM outputs.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    DOI: 10.5194/tc-14-385-2020
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2393169-3
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  • 3
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    Representative surface snow density on the East Antarctic Plateau
    Copernicus GmbH ; 2020
    In:  The Cryosphere Vol. 14, No. 11 ( 2020-11-05), p. 3663-3685
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 14, No. 11 ( 2020-11-05), p. 3663-3685
    Abstract: Abstract. Surface mass balances of polar ice sheets are essential to estimate the contribution of ice sheets to sea level rise. Uncertain snow and firn densities lead to significant uncertainties in surface mass balances, especially in the interior regions of the ice sheets, such as the East Antarctic Plateau (EAP). Robust field measurements of surface snow density are sparse and challenging due to local noise. Here, we present a snow density dataset from an overland traverse in austral summer 2016/17 on the Dronning Maud Land plateau. The sampling strategy using 1 m carbon fiber tubes covered various spatial scales, as well as a high-resolution study in a trench at 79∘ S, 30∘ E. The 1 m snow density has been derived volumetrically, and vertical snow profiles have been measured using a core-scale microfocus X-ray computer tomograph. With an error of less than 2 %, our method provides higher precision than other sampling devices of smaller volume. With four spatially independent snow profiles per location, we reduce the local noise and derive a representative 1 m snow density with an error of the mean of less than 1.5 %. Assessing sampling methods used in previous studies, we find the highest horizontal variability in density in the upper 0.3 m and therefore recommend the 1 m snow density as a robust measure of surface snow density in future studies. The average 1 m snow density across the EAP is 355 kg m−3, which we identify as representative surface snow density between Kohnen Station and Dome Fuji. We cannot detect a temporal trend caused by the temperature increase over the last 2 decades. A difference of more than 10 % to the density of 320 kg m−3 suggested by a semiempirical firn model for the same region indicates the necessity for further calibration of surface snow density parameterizations. Our data provide a solid baseline for tuning the surface snow density parameterizations for regions with low accumulation and low temperatures like the EAP.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    DOI: 10.5194/tc-14-3663-2020
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
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  • 4
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    Promising Oldest Ice sites in East Antarctica based on thermodynamical modelling
    Copernicus GmbH ; 2018
    In:  The Cryosphere Vol. 12, No. 8 ( 2018-08-30), p. 2773-2787
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 12, No. 8 ( 2018-08-30), p. 2773-2787
    Abstract: Abstract. To resolve the mechanisms behind the major climate reorganisation, which occurred between 0.9 and 1.2 Ma, the recovery of a suitable 1.5 million-year-old ice core is fundamental. The quest for an Oldest Ice core requires a number of key boundary conditions, of which the poorly known basal geothermal heat flux (GHF) is lacking. We use a transient thermodynamical 1-D vertical model that solves for the rate of change of temperature in the vertical, with surface temperature and modelled GHF as boundary conditions. For each point on the ice sheet, the model is forced with variations in atmospheric conditions over the last 2 Ma and modelled ice-thickness variations. The process is repeated for a range of GHF values to determine the value of GHF that marks the limit between frozen and melting conditions over the whole ice sheet, taking into account 2 Ma of climate history. These threshold values of GHF are statistically compared to existing GHF data sets. The new probabilistic GHF fields obtained for the ice sheet thus provide the missing boundary conditions in the search for Oldest Ice. High spatial resolution radar data are examined locally in the Dome Fuji and Dome C regions, as these represent the ice core community's primary drilling sites. GHF, bedrock variability, ice thickness and other essential criteria combined highlight a dozen major potential Oldest Ice sites in the vicinity of Dome Fuji and Dome C, where GHF could allow for Oldest Ice.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    DOI: 10.5194/tc-12-2773-2018
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
    detail.hit.zdb_id: 2393169-3
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  • 5
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    Reviews and syntheses: A framework to observe, understand and project ecosystem response to environmental change in the East Antarctic Southern Ocean
    Copernicus GmbH ; 2022
    In:  Biogeosciences Vol. 19, No. 22 ( 2022-11-23), p. 5313-5342
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 19, No. 22 ( 2022-11-23), p. 5313-5342
    Abstract: Abstract. Systematic long-term studies on ecosystem dynamics are largely lacking from the East Antarctic Southern Ocean, although it is well recognized that they are indispensable to identify the ecological impacts and risks of environmental change. Here, we present a framework for establishing a long-term cross-disciplinary study on decadal timescales. We argue that the eastern Weddell Sea and the adjacent sea to the east, off Dronning Maud Land, is a particularly well suited area for such a study, since it is based on findings from previous expeditions to this region. Moreover, since climate and environmental change have so far been comparatively muted in this area, as in the eastern Antarctic in general, a systematic long-term study of its environmental and ecological state can provide a baseline of the current situation, which will be important for an assessment of future changes from their very onset, with consistent and comparable time series data underpinning and testing models and their projections. By establishing an Integrated East Antarctic Marine Research (IEAMaR) observatory, long-term changes in ocean dynamics, geochemistry, biodiversity, and ecosystem functions and services will be systematically explored and mapped through regular autonomous and ship-based synoptic surveys. An associated long-term ecological research (LTER) programme, including experimental and modelling work, will allow for studying climate-driven ecosystem changes and interactions with impacts arising from other anthropogenic activities. This integrative approach will provide a level of long-term data availability and ecosystem understanding that are imperative to determine, understand, and project the consequences of climate change and support a sound science-informed management of future conservation efforts in the Southern Ocean.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    DOI: 10.5194/bg-19-5313-2022
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
    detail.hit.zdb_id: 2158181-2
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  • 6
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    Mapping age and basal conditions of ice in the Dome Fuji region, Antarctica, by combining radar internal layer stratigraphy and flow modeling
    Copernicus GmbH ; 2023
    In:  The Cryosphere Vol. 17, No. 10 ( 2023-10-10), p. 4297-4314
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 17, No. 10 ( 2023-10-10), p. 4297-4314
    Abstract: Abstract. The Dome Fuji (DF) region in Antarctica is a potential site for an ice core with a record of over 1 Myr. Here, we combine large-scale internal airborne radar stratigraphy with a 1-D model to estimate the age of basal ice in the DF region. The radar data used in the study were collected in a survey during the 2016–2017 Antarctic season. We transfer the latest age–depth scales from the DF ice core to isochrones traced in radargrams in the surrounding 500 km × 550 km region. At each point of the survey the 1-D model uses the ages of isochrones to construct the age–depth scale at depths where dated isochrones do not exist, the surface accumulation rate and the basal thermal condition, including melt rate and the thickness of stagnant ice. Our resulting age distribution and age density suggest that several promising sites with ice older than 1.5 Myr in the DF region might exist. The deduced melt rates and presence of stagnant ice provide more constraints for locating sites with a cold base. The accumulation rates range from 0.015 to 0.038 m a−1 ice equivalent. Based on sensitivity studies we find that the number and depth of picked isochrones and the timescale of the ice core severely affect the model results. Our study demonstrates that constraints from deep radar isochrones and a trustworthy timescale could improve the model estimation to find old ice in the DF region.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    URL: Article
    DOI: 10.5194/tc-17-4297-2023
    DOI: 10.5194/tc-17-4297-2023-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2023
    detail.hit.zdb_id: 2393169-3
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  • 7
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    The regional-scale surface mass balance of Pine Island Glacier, West Antarctica, over the period 2005–2014, derived from airborne radar soundings and neutron probe measurements
    Copernicus GmbH ; 2021
    In:  The Cryosphere Vol. 15, No. 3 ( 2021-03-11), p. 1285-1305
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 15, No. 3 ( 2021-03-11), p. 1285-1305
    Abstract: Abstract. We derive recent surface mass balance (SMB) estimates from airborne radar observations along the iSTAR traverse (2013, 2014) at Pine Island Glacier (PIG), West Antarctica. Ground-based neutron probe measurements provide information of snow and firn density with depth at 22 locations and were used to date internal annual reflection layers. The 2005 layer was traced for a total distance of 2367 km to determine annual mean SMB for the period 2005–2014. Using complementary SMB estimates from two regional climate models, RACMO2.3p2 and MAR, and a geostatistical kriging scheme, we determine a regional-scale SMB distribution with similar main characteristics to that determined for the period 1985–2009 in previous studies. Local departures exist for the northern PIG slopes, where the orographic precipitation shadow effect appears to be more pronounced in our observations, and the southward interior, where the SMB gradient is more pronounced in previous studies. We derive total mass inputs of 79.9±19.2 and 82.1±19.2 Gt yr−1 to the PIG basin based on complementary ASIRAS–RACMO and ASIRAS–MAR SMB estimates, respectively. These are not significantly different to the value of 78.3±6.8 Gt yr−1 for the period 1985–2009. Thus, there is no evidence of a secular trend at decadal scales in total mass input to the PIG basin. We note, however, that our estimated uncertainty is more than twice the uncertainty for the 1985–2009 estimate on total mass input. Our error analysis indicates that uncertainty estimates on total mass input are highly sensitive to the selected krige methodology and assumptions made on the interpolation error, which we identify as the main cause for the increased uncertainty range compared to the 1985–2009 estimates.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    URL: Article
    DOI: 10.5194/tc-15-1285-2021
    DOI: 10.5194/tc-15-1285-2021-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
    detail.hit.zdb_id: 2393169-3
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  • 8
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    Age stratigraphy in the East Antarctic Ice Sheet inferred from radio-echo sounding horizons
    Copernicus GmbH ; 2019
    In:  Earth System Science Data Vol. 11, No. 3 ( 2019-07-18), p. 1069-1081
    Details
    In: Earth System Science Data, Copernicus GmbH, Vol. 11, No. 3 ( 2019-07-18), p. 1069-1081
    Abstract: Abstract. The East Antarctic Ice Sheet contains a wealth of information that can be extracted from its internal architecture such as distribution of age, past flow features, and surface and basal properties. Airborne radar surveys can sample this stratigraphic archive across broad areas. Here, we identify and trace key horizons across several radar surveys to obtain the stratigraphic information. We transfer the age–depth scales from ice cores to intersecting radar data. We then propagate these age scales across the ice sheet using the high fidelity continuity of the radar horizons. In Dronning Maud Land, including Dome Fuji, we mapped isochrones with ages of 38 and 74 ka. In the central region of East Antarctica around Dome Concordia, Vostok and Dome Argus, we use isochrone ages of 38, 48, 90 and 161 ka. Taking together both regions, we provide isochrone depths traced along a combined profile length of more than 40 000 km and discuss uncertainties of the obtained stratigraphy, as well as factors important to consider for further expansion. This data set is the most extensive distribution of internal horizons in East Antarctica to date. The isochrone depths presented in this study are available on PANGAEA (https://doi.org/10.1594/PANGAEA.895528; Winter et al., 2018).
    Type of Medium: Online Resource
    ISSN: 1866-3516
    URL: Article
    DOI: 10.5194/essd-11-1069-2019
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2475469-9
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  • 9
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    Investigating the internal structure of the Antarctic ice sheet: the utility of isochrones for spatiotemporal ice-sheet model calibration
    Copernicus GmbH ; 2021
    In:  The Cryosphere Vol. 15, No. 8 ( 2021-08-18), p. 3839-3860
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 15, No. 8 ( 2021-08-18), p. 3839-3860
    Abstract: Abstract. Ice-sheet models are a powerful tool to project the evolution of the Greenland and Antarctic ice sheets and thus their future contribution to global sea-level changes. Testing the ability of ice-sheet models to reproduce the ongoing and past evolution of the ice cover in Greenland and Antarctica is a fundamental part of every modelling effort. However, benchmarking ice-sheet model results against real-world observations is a non-trivial process as observational data come with spatiotemporal gaps in coverage. Here, we present a new approach to assess the accuracy of ice-sheet models which makes use of the internal layering of the Antarctic ice sheet. We calculate isochrone elevations from simulated Antarctic geometries and velocities via passive Lagrangian tracers, highlighting that a good fit of the model to two-dimensional datasets such as surface velocity and ice thickness does not guarantee a good match against the 3D architecture of the ice sheet and thus correct evolution over time. We show that palaeoclimate forcing schemes derived from ice-core records and climate models commonly used to drive ice-sheet models work well to constrain the 3D structure of ice flow and age in the interior of the East Antarctic ice sheet and especially along ice divides but fail towards the ice-sheet margin. The comparison to isochronal horizons attempted here reveals that simple heuristics of basal drag can lead to an overestimation of the vertical interior ice-sheet flow especially over subglacial basins. Our model observation intercomparison approach opens a new avenue for the improvement and tuning of current ice-sheet models via a more rigid constraint on model parameterisations and climate forcing, which will benefit model-based estimates of future and past ice-sheet changes.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    DOI: 10.5194/tc-15-3839-2021
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
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  • 10
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    Airborne ultra-wideband radar sounding over the shear margins and along flow lines at the onset region of the Northeast Greenland Ice Stream
    Copernicus GmbH ; 2022
    In:  Earth System Science Data Vol. 14, No. 2 ( 2022-02-21), p. 763-779
    Details
    In: Earth System Science Data, Copernicus GmbH, Vol. 14, No. 2 ( 2022-02-21), p. 763-779
    Abstract: 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 the Alfred Wegener Institute's multichannel ultra-wideband (UWB) radar mounted on the Polar 6 aircraft. Radar profiles cover an area of ∼24 000 km2 and extend over the well-defined shear margins of the NEGIS. The survey area is centered 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 cannot 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 modeled 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 from the PANGAEA data publisher (https://doi.pangaea.de/10.1594/PANGAEA.928569; Franke et al., 2021a).
    Type of Medium: Online Resource
    ISSN: 1866-3516
    URL: Article
    DOI: 10.5194/essd-14-763-2022
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
    detail.hit.zdb_id: 2475469-9
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