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  1. Article ; Online: Spatial characterization of near-surface structure and meltwater runoff conditions across the Devon Ice Cap from dual-frequency radar reflectivity

    K. Chan / C. Grima / A. Rutishauser / D. A. Young / R. Culberg / D. D. Blankenship

    The Cryosphere, Vol 17, Pp 1839-

    2023  Volume 1852

    Abstract: Melting and refreezing processes in the firn of the Devon Ice Cap control meltwater infiltration and runoff across the ice cap, but their full spatial extent and effect on near-surface structure is difficult to measure with surface-based traverses or ... ...

    Abstract Melting and refreezing processes in the firn of the Devon Ice Cap control meltwater infiltration and runoff across the ice cap, but their full spatial extent and effect on near-surface structure is difficult to measure with surface-based traverses or existing satellite remote sensing. Here, we derive the coherent component of the near-surface return from airborne ice-penetrating radar surveys over the Devon Ice Cap, Canadian Arctic, to characterize firn containing centimeter- to meter-thick ice layers (i.e., ice slabs) formed from refrozen meltwater in firn. We assess the use of dual-frequency airborne ice-penetrating radar to characterize the spatial and vertical near-surface structure of the Devon Ice Cap by leveraging differences in range resolution of the radar systems. Comparison with reflectivities using a thin layer reflectivity model, informed by surface-based radar and firn core measurements, indicates that the coherent component is sensitive to the near-surface firn structure composed of quasi-specular ice and firn layers, limited by the bandwidth-constrained radar range resolution. Our results suggest that average ice slab thickness throughout the Devon Ice Cap percolation zone ranges from 4.2 to 5.6 m. This implies conditions that can enable lateral meltwater runoff and potentially contribute to the total surface runoff routed through supraglacial rivers down glacier. Together with the incoherent component of the surface return previously studied, our dual-frequency approach provides an alternative method for characterizing bulk firn properties, particularly where high-resolution radar data are not available.
    Keywords Environmental sciences ; GE1-350 ; Geology ; QE1-996.5
    Subject code 550
    Language English
    Publishing date 2023-05-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article: Effect of Graphene Nanoparticles on the Physical Properties of Ophthalmic Polymer Containing Pyrrolidone Group.

    Kim, Duck-Hyun / Seok, Jae-Wuk / Sung, D A-Young

    Journal of nanoscience and nanotechnology

    2019  Volume 19, Issue 10, Page(s) 6516–6523

    Abstract: In this study, the functional ophthalmic hydrogel lens containing graphen oxide nanoparticles, PVP (polyvinylpyrrolidone) were manufactured. For 2-hydroxyethyl methacrylate (HEMA), which is the main component of the ophthalmic hydrogel lens, and ... ...

    Abstract In this study, the functional ophthalmic hydrogel lens containing graphen oxide nanoparticles, PVP (polyvinylpyrrolidone) were manufactured. For 2-hydroxyethyl methacrylate (HEMA), which is the main component of the ophthalmic hydrogel lens, and azobisisobutyronitrile (AIBN), an initiator for thermal polymerization. And for photopolymerization, 2-hydroxy-2-methylpropiophenone (2H2M). And used for cross linker ethylene glycol dimethacrylate (EGDMA). The prepared ophthalmic hydrogel lens samples were hydrated in a sterile physiological saline solution for 24 hours before evaluating their physical properties, such as optical transmittance, refractive index, and water content. The surface characteristics of the lenses were also evaluated by measuring the AFM and contact angle. The results of this study suggest that PVP and graphene oxide nanoparticles have high wettability as additives, and that the lens manufactured by using the photopolymerization method demonstrated an ultraviolet shielding effect, thereby prompting us to conclude its suitability as a highly functional ophthalmic lens.
    MeSH term(s) Graphite ; Hydrogels ; Nanoparticles ; Polymerization ; Polymers
    Chemical Substances Hydrogels ; Polymers ; Graphite (7782-42-5)
    Language English
    Publishing date 2019-04-22
    Publishing country United States
    Document type Journal Article
    ISSN 1533-4880
    ISSN 1533-4880
    DOI 10.1166/jnn.2019.17074
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: High mid-Holocene accumulation rates over West Antarctica inferred from a pervasive ice-penetrating radar reflector

    J. A. Bodart / R. G. Bingham / D. A. Young / J. A. MacGregor / D. W. Ashmore / E. Quartini / A. S. Hein / D. G. Vaughan / D. D. Blankenship

    The Cryosphere, Vol 17, Pp 1497-

    2023  Volume 1512

    Abstract: Understanding the past and future evolution of the Antarctic Ice Sheet is challenged by the availability and quality of observed paleo-boundary conditions. Numerical ice-sheet models often rely on these paleo-boundary conditions to guide and evaluate ... ...

    Abstract Understanding the past and future evolution of the Antarctic Ice Sheet is challenged by the availability and quality of observed paleo-boundary conditions. Numerical ice-sheet models often rely on these paleo-boundary conditions to guide and evaluate their models' predictions of sea-level rise, with varying levels of confidence due to the sparsity of existing data across the ice sheet. A key data source for large-scale reconstruction of past ice-sheet processes are internal reflecting horizons (IRHs) detected by radio-echo sounding (RES). When IRHs are isochronal and dated at ice cores, they can be used to determine paleo-accumulation rates and patterns on large spatial scales. Using a spatially extensive IRH over the Pine Island Glacier (PIG), Thwaites Glacier (THW), and the Institute and Möller ice streams (IMIS, covering a total of 610 000 km 2 or 30 % of the West Antarctic Ice Sheet (WAIS)), and a local layer approximation model, we infer mid-Holocene accumulation rates over the slow-flowing parts of these catchments for the past ∼4700 years. By comparing our results with modern climate reanalysis models (1979–2019) and observational syntheses (1651–2010), we estimate that accumulation rates over the Amundsen–Weddell–Ross Divide were on average 18 % higher during the mid-Holocene than modern rates. However, no significant spatial changes in the accumulation pattern were observed. The higher mid-Holocene accumulation-rate estimates match previous paleo-accumulation estimates from ice-core records and targeted RES surveys over the ice divide, and they also coincide with periods of grounding-line readvance during the Holocene over the Weddell and Ross sea sectors. We find that our spatially extensive, mid-Holocene-to-present accumulation estimates are consistent with a sustained late-Holocene period of higher accumulation rates occurring over millennia reconstructed from the WAIS Divide ice core (WD14), thus indicating that this ice core is spatially representative of the wider West Antarctic region. We ...
    Keywords Environmental sciences ; GE1-350 ; Geology ; QE1-996.5
    Subject code 910
    Language English
    Publishing date 2023-04-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Aerogeophysical characterization of Titan Dome, East Antarctica, and potential as an ice core target

    L. H. Beem / D. A. Young / J. S. Greenbaum / D. D. Blankenship / M. G. P. Cavitte / J. Guo / S. Bo

    The Cryosphere, Vol 15, Pp 1719-

    2021  Volume 1730

    Abstract: Based on sparse data, Titan Dome has been identified as having a higher probability of containing ice that would capture the middle Pleistocene transition (1.25 to 0.7 Ma). New aerogeophysical observations (radar and laser altimetry) collected over Titan ...

    Abstract Based on sparse data, Titan Dome has been identified as having a higher probability of containing ice that would capture the middle Pleistocene transition (1.25 to 0.7 Ma). New aerogeophysical observations (radar and laser altimetry) collected over Titan Dome, located about 200 km from the South Pole within the East Antarctic Ice Sheet, were used to characterize the region (e.g., geometry, internal structure, bed reflectivity, and flow history) and assess its suitability as a paleoclimate ice core site. The radar coupled with an available ice core chronology enabled the tracing of dated internal reflecting horizons throughout the region, which also served as constraints on basal ice age modeling. The results of the survey revealed new basal topographic detail and better constrain the ice topographical location of Titan Dome, which differs between community datasets. Titan Dome is not expected to be relevant to the study of the middle Pleistocene transition due to a combination of past fast flow dynamics, the basal ice likely being too young, and the temporal resolution likely being too coarse if 1 Ma ice were to exist.
    Keywords Environmental sciences ; GE1-350 ; Geology ; QE1-996.5
    Subject code 290
    Language English
    Publishing date 2021-04-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Radar sounding survey over Devon Ice Cap indicates the potential for a diverse hypersaline subglacial hydrological environment

    A. Rutishauser / D. D. Blankenship / D. A. Young / N. S. Wolfenbarger / L. H. Beem / M. L. Skidmore / A. Dubnick / A. S. Criscitiello

    The Cryosphere, Vol 16, Pp 379-

    2022  Volume 395

    Abstract: Prior geophysical surveys provided evidence for a hypersaline subglacial lake complex beneath the center of Devon Ice Cap, Canadian Arctic; however, the full extent and characteristics of the hydrological system remained unknown due to limited data ... ...

    Abstract Prior geophysical surveys provided evidence for a hypersaline subglacial lake complex beneath the center of Devon Ice Cap, Canadian Arctic; however, the full extent and characteristics of the hydrological system remained unknown due to limited data coverage. Here, we present results from a new, targeted aerogeophysical survey that provides evidence (i) supporting the existence of a subglacial lake complex and (ii) for a network of shallow brine/saturated sediments covering ∼170 km 2 . Newly resolved lake shorelines indicate three closely spaced lakes covering a total area of 24.6 km 2 . These results indicate the presence of a diverse hypersaline subglacial hydrological environment with the potential to support a range of microbial habitats, provide important constraints for future investigations of this compelling scientific target, and highlight its relevance as a terrestrial analog for aqueous systems on other icy worlds.
    Keywords Environmental sciences ; GE1-350 ; Geology ; QE1-996.5
    Subject code 333
    Language English
    Publishing date 2022-02-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: Seasonal dynamics of Totten Ice Shelf controlled by sea ice buttressing

    C. A. Greene / D. A. Young / D. E. Gwyther / B. K. Galton-Fenzi / D. D. Blankenship

    The Cryosphere, Vol 12, Pp 2869-

    2018  Volume 2882

    Abstract: Previous studies of Totten Ice Shelf have employed surface velocity measurements to estimate its mass balance and understand its sensitivities to interannual changes in climate forcing. However, displacement measurements acquired over timescales of days ... ...

    Abstract Previous studies of Totten Ice Shelf have employed surface velocity measurements to estimate its mass balance and understand its sensitivities to interannual changes in climate forcing. However, displacement measurements acquired over timescales of days to weeks may not accurately characterize long-term flow rates wherein ice velocity fluctuates with the seasons. Quantifying annual mass budgets or analyzing interannual changes in ice velocity requires knowing when and where observations of glacier velocity could be aliased by subannual variability. Here, we analyze 16 years of velocity data for Totten Ice Shelf, which we generate at subannual resolution by applying feature-tracking algorithms to several hundred satellite image pairs. We identify a seasonal cycle characterized by a spring to autumn speedup of more than 100 m yr −1 close to the ice front. The amplitude of the seasonal cycle diminishes with distance from the open ocean, suggesting the presence of a resistive back stress at the ice front that is strongest in winter. Springtime acceleration precedes summer surface melt and is not attributable to thinning from basal melt. We attribute the onset of ice shelf acceleration each spring to the loss of buttressing from the breakup of seasonal landfast sea ice.
    Keywords Environmental sciences ; GE1-350 ; Geology ; QE1-996.5
    Language English
    Publishing date 2018-09-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  7. Article ; Online: Promising Oldest Ice sites in East Antarctica based on thermodynamical modelling

    B. Van Liefferinge / F. Pattyn / M. G. P. Cavitte / N. B. Karlsson / D. A. Young / J. Sutter / O. Eisen

    The Cryosphere, Vol 12, Pp 2773-

    2018  Volume 2787

    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 ... ...

    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.
    Keywords Environmental sciences ; GE1-350 ; Geology ; QE1-996.5
    Subject code 290
    Language English
    Publishing date 2018-08-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  8. Article ; Online: Surface and basal boundary conditions at the Southern McMurdo and Ross Ice Shelves, Antarctica – CORRIGENDUM

    C. Grima / I. Koch / J. S. Greenbaum / K. M. Soderlund / D. D. Blankenship / D. A. Young / D. M. Schroeder / S. Fitzsimons

    Journal of Glaciology, Vol 66, Pp 348-

    2020  Volume 348

    Keywords Environmental sciences ; GE1-350 ; Meteorology. Climatology ; QC851-999
    Language English
    Publishing date 2020-04-01T00:00:00Z
    Publisher Cambridge University Press
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  9. Article ; Online: Aerogeophysical characterization of an active subglacial lake system in the David Glacier catchment, Antarctica

    L. E. Lindzey / L. H. Beem / D. A. Young / E. Quartini / D. D. Blankenship / C.-K. Lee / W. S. Lee / J. I. Lee / J. Lee

    The Cryosphere, Vol 14, Pp 2217-

    2020  Volume 2233

    Abstract: In the 2016–2017 austral summer, the University of Texas Institute for Geophysics (UTIG) and the Korea Polar Research Institute (KOPRI) collaborated to perform a helicopter-based radar and laser altimeter survey of lower David Glacier with the goals of ... ...

    Abstract In the 2016–2017 austral summer, the University of Texas Institute for Geophysics (UTIG) and the Korea Polar Research Institute (KOPRI) collaborated to perform a helicopter-based radar and laser altimeter survey of lower David Glacier with the goals of characterizing the subglacial water distribution that supports a system of active subglacial lakes and informing the site selection for a potential subglacial access drilling project. This survey overlaps with and expands upon an earlier survey of the Drygalski Ice Tongue and the David Glacier grounding zone from 2011 and 2012 to create a 5 km resolution survey extending 200 km upstream from the grounding zone. The surveyed region covers two active subglacial lakes and includes reflights of ICESat ground tracks that extend the surface elevation record in the region. This is one of the most extensive aerogeophysical surveys of an active lake system and provides higher-resolution boundary conditions and basal characterizations that will enable process studies of these features. This paper introduces a new helicopter-mounted ice-penetrating radar and laser altimetry system, notes a discrepancy between the original surface-elevation-derived lake outlines and locations of possible water collection based on basal geometry and hydraulic potential, and presents radar-based observations of basal conditions that are inconsistent with large collections of ponded water despite laser altimetry showing that the hypothesized active lakes are at a highstand.
    Keywords Environmental sciences ; GE1-350 ; Geology ; QE1-996.5
    Subject code 550
    Language English
    Publishing date 2020-07-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  10. Article ; Online: Surface and basal boundary conditions at the Southern McMurdo and Ross Ice Shelves, Antarctica

    C. GRIMA / I. KOCH / J. S. GREENBAUM / K. M. SODERLUND / D. D. BLANKENSHIP / D. A. YOUNG / D. M. SCHROEDER / S. FITZSIMONS

    Journal of Glaciology, Vol 65, Pp 675-

    2019  Volume 688

    Abstract: We derive the surface and basal radar reflectance and backscatter coefficients of the southern McMurdo Ice Shelf (SMIS) and part of the nearby Ross Ice Shelf (RIS), Antarctica, from radar statistical reconnaissance using a 60-MHZ airborne survey. The ... ...

    Abstract We derive the surface and basal radar reflectance and backscatter coefficients of the southern McMurdo Ice Shelf (SMIS) and part of the nearby Ross Ice Shelf (RIS), Antarctica, from radar statistical reconnaissance using a 60-MHZ airborne survey. The surface coefficients are further inverted in terms of snow density and roughness, providing a spatial distribution of the processes contributing to the surface boundary conditions. We disentangle the basal coefficients from surface transmission losses, and we provide the basal coherent content, an indicator of the boundary geometric disorder that is also self-corrected from englacial attenuation. The basal radar properties exhibit sharp gradients along specific iso-depths, suggesting an abrupt modification of the ice composition and geometric structure. We interpret this behavior as locations where the pressure-melting point is reached, outlining fields of freezing and melting ice. Basal steps are observed at both SMIS and RIS, suggesting a common geometric expression of widespread basal processes. This technique offers a simultaneous view of both the surface and basal boundary conditions to help investigate the ice-shelf stability, while its application to airborne data significantly improves coverage of the difficult-to-observe ice–ocean boundary. It also provides constraints on thermohaline circulation in ice shelves cavities, which are analogs for ice-covered ocean worlds.
    Keywords basal ; ice shelf ; processes ; radar ; roughness ; surface ; Environmental sciences ; GE1-350 ; Meteorology. Climatology ; QC851-999
    Subject code 550
    Language English
    Publishing date 2019-08-01T00:00:00Z
    Publisher Cambridge University Press
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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