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  • 1
    Publication Date: 2016-04-06
    Description: Changes observed in the West Antarctic Ice Sheet (WAIS) and Antarctic Peninsula Ice Sheet (APIS) over recent decades include thinning and break up of ice shelves, glacier flow acceleration and grounding line retreat. How rapidly and how far these ice sheets will retreat in a warmer climate, however, remains uncertain. For example, it remains unclear whether or not the marine-based WAIS “collapsed” during Quaternary interglacial periods, including the last one, contributing more than 3 m to global sea-level rise. Continuous long-term records of ice sheet change with precise chronology are needed in order to answer these questions. On the Antarctic continental shelf, sedimentary records are interrupted by numerous unconformities resulting from glacial erosion, good core recovery has only been achieved from platforms sited on sea ice or ice shelves, and establishing reliable chronologies has proved challenging. In contrast, sediment drifts on the upper continental rise around Antarctica contain expanded, continuous successions dominated by muddy lithologies from which good recovery can be achieved using standard scientific ocean drilling methods. Ocean Drilling Program (ODP) Leg 178 demonstrated that sediment drifts west of the Antarctic Peninsula contain a rich high-resolution archive of Southern Ocean paleoceanography and APIS history that extends back to at least the late Miocene. The potential of existing ODP cores from the drifts is, however, compromised by incomplete composite sections and lack of precise chronological control. An International Ocean Discovery Program proposal (732-Full2) for future drilling on these drifts has been scientifically approved and is with the JOIDES Resolution Facilities Board for scheduling. The main aims of the proposal are to obtain continuous, high-resolution records from sites on sediment drifts off both the Antarctic Peninsula and West Antarctica (southern Bellingshausen Sea). The challenges will then be achieving good chronological control using a range of established and novel techniques and interpreting what facies variations indicate in terms of changes in the ice sheets. During a 2015 research cruise on RRS James Clark Ross (JR298) we obtained additional site survey data around the proposed sites including high-resolution multichannel seismic reflection data, piston cores and box cores. We will present results from this cruise and interpret them in terms of sedimentary processes that operated during the development of the drifts, and links between depositional systems on the continental rise, paleoice-sheet dynamics and paleoceanographic processes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 2
    Publication Date: 2018-08-10
    Description: We will present new multibeam bathymetry data that make the Anvers-Hugo Trough west of the Antarctic Peninsula one of the most completely surveyed palaeo-ice stream pathways in Antarctica. We interpret landforms revealed by these data as indicating that subglacial water availability played an important role in facilitating ice stream flow in the trough during late Quaternary glacial periods. Specifically, we observe a set of northward-shoaling valleys that are eroded into the upstream edge of a sedimentary basin, extend northwards from a zone containing landforms typical of erosion by subglacial water flow, and coincide spatially with the onset of mega-scale glacial lineations. Water was likely supplied to the ice stream bed episodically as a result of outbursts from a subglacial lake previously hypothesized to have been located in the Palmer Deep basin on the inner continental shelf. In a palaeo-ice stream confluence area, close juxtaposition of mega-scale glacial lineations with landforms that are characteristic of slow, dry-based ice flow, suggests that water availability was also an important control on the lateral extent of these palaeo-ice streams. These interpretations are consistent with the hypothesis that subglacial lakes or areas of elevated geothermal heat flux play a critical role in the onset of many large ice streams. The interpretations also have implications for the dynamic behaviour of the Anvers-Hugo Trough palaeo-ice stream and, potentially, of several other Antarctic palaeo-ice streams. Keywords: multibeam bathymetry, ice stream, subglacial water, landform
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
    Format: application/pdf
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  • 3
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    PANGAEA
    In:  Supplement to: Hogan, Kelly A; Dowdeswell, Julian A; Noormets, R; Evans, Jeffrey; Ó'Cofaigh, Colm; Jakobsson, Martin (2010): Submarine landforms and ice-sheet flow in the Kvitøya Trough, northwestern Barents Sea. Quaternary Science Reviews, 29(25-26), 3545-3562, https://doi.org/10.1016/j.quascirev.2010.08.015
    Publication Date: 2020-01-18
    Description: High-resolution geophysical and sediment core data are used to investigate the pattern and dynamics of former ice flow in Kvitøya Trough, northwestern Barents Sea. A new swath-bathymetric dataset identifies three types of submarine landform in the study area (streamlined landforms, meltwater channels and cavities, iceberg scours). Subglacially produced streamlined landforms provide a record of ice flow through Kvitøya Trough during the last glaciation. Flow directions are inferred from the orientations of streamlined landforms (drumlins, crag-and-tail features). Ice flowed northward for at least 135 km from an ice divide at the southern end of Kvitøya Trough. A large channel-cavity system incised into bedrock in the southern trough indicates that subglacial meltwater was present at the former ice-sheet base. Modest landform elongation ratios and a lack of mega-scale glacial lineations suggest that, although ice in Kvitøya Trough was melting at the bed and flowed faster than the likely thin and cold-based ice on adjacent banks, a major ice stream probably did not occupy the trough. Retreat was relatively rapid after 14-13.5 14C kyr B.P. and probably progressed via ice sheet-bed decoupling in response to rising sea level. There is little evidence for still stands during ice retreat or of ice-proximal deglacial sediments. Relict iceberg scours in present-day water depths of more than 350 m in the northern trough indicate that calving was an important mass loss mechanism during retreat.
    Type: Dataset
    Format: text/tab-separated-values, 12 data points
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  • 4
    Publication Date: 2018-08-12
    Description: It is becoming increasingly apparent that bathymetry plays a crucial role in determining the behavior of marine-terminating glaciers. This is because variations in the shape of the bed can produce both pinning points where glaciers (or their floating tongues) can ground and stabilize, as well as pathways for warm waters to move across the shelf and access the grounding line. Ahead of the first ITGC field season we present the existing state of knowledge about the bed in front of Thwaites Glacier (TG). We have compiled existing multibeam-bathymetric datasets from the UK, the USA and international partners (Korea, Germany) to produce a high-resolution grid (50-m cells) for the area. From this grid we identify possible pathways for warm Circumpolar Deep Water to the TG grounding line, a topographic high – as shallow as 130 m in places - that likely acted as a pinning point and is less than 18 km from the current eastern ice-shelf margin, and landforms indicative of the past behavior of the glacier (e.g. meltwater channels and basins, streamlined landforms). This exercise also highlights important data gaps to target for surveying in 2019, including for example, the area left vacant by the calving of the B-22 iceberg. Secondly, we explore existing sub-bottom and seismic-reflection profiles from the Amundsen Sea Embayment to investigate the nature of the substrate in front of TG. Unlithified sediment cover is generally thin (〈5 m) over scoured crystalline bedrock but thickens to up to 40 m in basins. We discuss potential coring targets close to pathways for warm water incursions, and former stability points including the possibility of unknown basins in front of TG.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 5
  • 6
    Publication Date: 2019-09-25
    Description: Late Miocene to Recent sediments offshore from the Antarctic Peninsula are predominantly lithogenic, having originated through glacial erosion. Sediments that accumulated during interglacial periods commonly have a greater biogenic component, but deposits in which this constitutes a substantial fraction are rare. Only a small fraction of the continental block is above sea level and even during interglacial periods temperatures are only warm enough to generate significant melt at low elevations for a few weeks each summer, so sediment input to the sea from surface runoff is minor. Sediment transport to the continental margin takes place mainly at the ice bed during glacial periods when the grounding line advances to the shelf edge. On the Pacific margin, downslope transport from the shelf edge region occurs mainly through gravitational mass transport processes. These processes are likely most active during glacial periods when rapid delivery of glacial sediment leads to instability on the uppermost slope and discharge of sediment-laden subglacial meltwater at the shelf edge grounding line initiates turbidity currents. The lack of obvious large slide scars along most of the relatively steep continental slope suggests that most individual failures are small in volume. Dendritic networks of small channels on the lower slope feed into large turbidity current channels that run out across the continental rise for hundreds of kilometres. Between the channels are giant sediment drifts, some with more than a kilometre of relief, which are composed predominantly of finely-bedded silt and clay layers. The drifts have been produced through entrainment of the fine-grained components of turbidity currents in the ambient bottom current that flows southwestward along the margin. Results from Ocean Drilling Program Leg 178 showed that these drifts contain high-resolution records of ice sheet and oceanographic changes, although unfortunately insufficient core material was recovered to generate continuous composite sections. During a 2015 research cruise on RRS James Clark Ross (JR298) we obtained new data over several of the drifts and channels, including high-resolution multichannel seismic reflection data, piston cores and box cores. We will present results from these new data, interpreting them in terms of sedimentary processes that operated during the development of the giant sediment drifts, and links between depositional systems on the continental rise, palaeo-ice-sheet dynamics and palaeoceanographic processes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 7
  • 8
    Publication Date: 2017-12-01
    Description: Greenland's bed topography is a primary control on ice flow, grounding line migration, calving dynamics and subglacial drainage. Moreover, fjord bathymetry regulates the penetration of warm Atlantic Water (AW) that rapidly melts and undercuts Greenland's marine-terminating glaciers. Here, we present a new compilation of Greenland bed topography that assimilates seafloor bathymetry and ice thickness data through a mass conservation (MC) approach. A new 150-m horizontal resolution bed topography/bathymetric map of Greenland is constructed with seamless transitions at the ice/ocean interface, yielding major improvements over previous datasets, particularly in the marine-terminating sectors of northwest and southeast Greenland. Our map reveals the total sea level potential of the Greenland Ice Sheet is 7.42±0.05 m, which is 7 cm greater than previous estimates. Furthermore, it explains recent calving front response of numerous outlet glaciers and reveals new pathways by which AW can access glaciers with marine-based basins, thereby highlighting sectors of Greenland that are most vulnerable to future oceanic forcing.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 9
    Publication Date: 2015-07-20
    Description: Observations across both the West Antarctic and Antarctic Peninsula ice sheets over recent decades have confirmed that the region is warming and undergoing major and potentially rapid changes as a result. These changes have manifest in the form of significant ice-sheet thinning and retreat, and in dramatic short-lived events such as ice-shelf collapses. The longer-term backdrop to this recent change is vital information for our understanding of future ice and climate evolution, and for wider knowledge of ice-sheet function and sensitivity. Providing context on geological timescales, such records can be obtained from two main sources: (1) from ice cores extracted from the ice sheet interiors and (2) from continuous marine sedimentary sequences recovered from the sea floor surrounding the Antarctic continent. Whilst ice cores provide a very high-resolution archive of palaeo-climate, they offer data over only a relatively short window of time (〈1 million years) and provide little information on how the ice and oceans were changing at the ice sheet periphery. By contrast, sediments derived from the Antarctic continent have discharged continuously to the continental slope and deeper ocean over millions of years, and are sensitive recorders of both ice sheet an oceanographic variability. Repeated continental margin-derived turbidity currents, in combination with the activity of along-slope currents, have led to the accumulation of large hemi-pelagic depositional bodies, termed sediment drifts that are, today, oriented orthogonal to the continental margin and record continuous sedimentation on the continental rise since at least the Miocene. Along the Antarctic Peninsula Pacific margin, a chain of twelve large sediment drifts separated out by channels eroded by turbidity currents provide unique archives of environmental changes in Antarctica‘s ice sheets and the Southern Ocean. IODP proposal 732FULL2 aims to recover drill cores extending back into the Pliocene from the crests of a number of the drifts, as well as from the top of the Belgica trough mouth fan, during a future leg to the region. Two further sites will recover older strata that can be accessed at relatively shallow depth by drilling through eroded drift flanks where the overburden is particularly thin. However, before recovering sequences from these bodies, a full understanding of their geometry, internal architecture, age and stratigraphic evolution is required. We present preliminary results from recent Natural Environment Research Council (UKIODP Programme) funded site survey cruise JR298 that obtained high-resolution multichannel seismic (MCS) reflection data over the proposed drill sites and adjacent working areas. A first look at the seismic data from several of the drilling targets will be presented, and some initial interpretations regarding the (i) sedimentary processes that operated during the formation and evolution of the drifts and fan, and (ii) links between depositional systems on the continental rise, palaeo-ice-sheet dynamics and past oceanographic processes within the datasets will be discussed. Further geophysical analyses, in combination with marine sediment cores retrieved from the proposed sites, will aim to shed light upon continental margin sediment delivery, Antarctic ice-sheet history and stability, and Antarctic margin palae-oceanography that form the key scientific objectives of the planned drilling campaign.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 10
    Publication Date: 2018-01-17
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geophysical Research Letters 44 (2017): 11,051–11,061, doi:10.1002/2017GL074954.
    Description: Greenland's bed topography is a primary control on ice flow, grounding line migration, calving dynamics, and subglacial drainage. Moreover, fjord bathymetry regulates the penetration of warm Atlantic water (AW) that rapidly melts and undercuts Greenland's marine-terminating glaciers. Here we present a new compilation of Greenland bed topography that assimilates seafloor bathymetry and ice thickness data through a mass conservation approach. A new 150 m horizontal resolution bed topography/bathymetric map of Greenland is constructed with seamless transitions at the ice/ocean interface, yielding major improvements over previous data sets, particularly in the marine-terminating sectors of northwest and southeast Greenland. Our map reveals that the total sea level potential of the Greenland ice sheet is 7.42 ± 0.05 m, which is 7 cm greater than previous estimates. Furthermore, it explains recent calving front response of numerous outlet glaciers and reveals new pathways by which AW can access glaciers with marine-based basins, thereby highlighting sectors of Greenland that are most vulnerable to future oceanic forcing.
    Description: National Aeronautics and Space Administration; Cryospheric Sciences Program Grant Number: NNX15AD55G; National Science Foundation's ARCSS program Grant Number: 1504230; NERC Grant Number: NE/M000869/1
    Keywords: Greenland ; Bathymetry ; Mass conservation ; Multibeam echo sounding ; Radar echo sounding ; Glaciology
    Repository Name: Woods Hole Open Access Server
    Type: Article
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