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  • 1
    Electronic Resource
    Electronic Resource
    Late Quaternary shedding of shallow-marine carbonate along a tropical mixed siliciclastic–carbonate shelf: Great Barrier Reef, Australia (2003)
    Oxford, UK : Blackwell Science Ltd
    Sedimentology 50 (2003), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract The north-east Australian margin is the largest modern example of a tropical mixed siliciclastic/carbonate depositional system, with an outer shelf hosting the Great Barrier Reef (GBR) and an inner shelf dominated by fluvially sourced siliciclastic sediment wedges. The long-term interplay between these sediment components and sea level is recorded in the Queensland Trough, a 1–2 km deep N–S elongate basin situated between the GBR platform and the Queensland Plateau. In this paper, 154 samples from 45 surface grabs and six well-dated piston cores were analysed for total carbonate content, carbonate mineralogy and Sr concentration to establish spatial and temporal patterns of carbonate accumulation in the Queensland Trough over the last 300 kyr. Surface carbonate contents are lowest on the inner-shelf (〈5%) and in the trough axis (〈60%) because of siliciclastic dilution. Carbonate on the shelf is mostly Sr-rich aragonite and high-Mg calcite (HMC), whereas that in the basin is mostly low-Mg calcite. Once normalized to remove the effects of siliciclastic dilution, surface Sr-rich aragonite and HMC abundances decrease linearly to background levels ≈ 100 km seaward of the shelf edge. Core samples show that, over time, normalized aragonite and Sr abundances are greatest during periods of shelf flooding and lowest when sea level drops below the shelf edge. This is consistent with changes in the production of coral and calcareous algae, and the shedding of their debris from the shelf. Interestingly, normalized HMC concentrations on the slope peak during periods of major transgression, perhaps because of maximum off-shelf transport from inter-reef areas or intermediate water dissolution. After accounting for siliciclastic dilution, there are strong similarities in both spatial and temporal patterns of carbonate minerals between slopes and basins of the north-east Australian margin and those of pure carbonate margins such as the Bahamas. A limited set of basic processes, including the formation and breakdown of carbonate on the shelf, the transport of carbonate off the shelf and eustatic sea level, probably controls carbonate accumulation in slope and basin settings of tropical environments, irrespective of proximal siliciclastic sediment sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3091.2003.00593.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Orbitally induced oscillations in the East Antarctic ice sheet at the Oligocene/Miocene boundary (2001)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 413 (2001), S. 719-723 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Between 34 and 15 million years (Myr) ago, when planetary temperatures were 3–4 °C warmer than at present and atmospheric CO2 concentrations were twice as high as today, the Antarctic ice sheets may have been unstable. Oxygen isotope records from deep-sea ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35099534
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  • 3
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    Reassessing the post-Last Glacial Maximum retreat history from the Southwest Ross Sea (2017)
    SCAR
    In:  EPIC3Past Antarctic Ice Sheet Dynamics (PAIS) Conference, Trieste, 2017-09-10-2017-09-15SCAR
    Details
    Publication Date: 2018-08-10
    Description: Constraining the timing of the retreat of the Last Glacial Maximum (LGM) Antarctic Ice Sheet in the Ross Sea provides insights into the processes controlling marine-based ice sheet retreat. The over-deepened Ross Sea continental shelf is an ideal configuration for marine ice-sheet instability, and this region was thought to be one of the largest Antarctic contributors to post-LGM sea level rise. However, the chronology and pattern of retreat of the LGM ice sheet in the Ross Sea is largely constrained by coastal records along the Transantarctic Mountain front in the Western Ross Sea. Although these offer more reliable dating techniques than marine sediment cores, they may be influenced by local glaciers derived from East Antarctic outlet glaciers. Consequently, these coastal records may be ambiguous in the broader context of retreat in the central regions of the Ross Sea. However, previous studies have inferred that records in this region retreated in a north to south pattern, and was fed by ice sourced from the central Ross Sea – with the implication that broader ice sheet retreat in the central Ross Sea occurred as late as the mid Holocene. We present two lines of evidence that counter this established interpretation of the pattern of retreat in the Ross Sea: 1) a sedimentary facies succession and foraminifera-based radiocarbon chronology from within the Ross Sea embayment that indicates glacial retreat and open marine conditions to the east of Ross Island was already in place before 8.6 cal ka BP, at least 1 kyr earlier than indicated by terrestrial records in McMurdo Sound; and 2) a new multibeam swath bathymetry data that identifies well-preserved glacial features indicating thick (〉700m) marine-based ice derived from the East Antarctic Ice Sheet (EAIS) coastal outlet glaciers dominated the ice sheet input into the southwestern Ross Sea during the last phases of glaciation – and thus may have acted independent of any ice in the central Ross Sea embayment. Comparing these data to new modelling experiments, we hypothesize that marine-based ice sheet retreat was triggered by oceanic forcings along most of the Pacific Ocean coastline of Antarctica, but continued early Holocene retreat into the inner shelf region of the Ross Sea occurred primarily as a consequence of marine ice sheet instability. Keywords: Ross Sea, deglaciation, Last Glacial Maximum, Holocene
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
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  • 4
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    Reassessing the post-Last Glacial Maximum retreat history from the Southwest Ross Sea (2017)
    SCAR
    In:  EPIC3Past Antarctic Ice Sheet Dynamics (PAIS) Conference, Trieste, 2017-09-10-2017-09-15SCAR
    Details
    Publication Date: 2018-08-10
    Description: Constraining the timing of the retreat of the Last Glacial Maximum (LGM) Antarctic Ice Sheet in the Ross Sea provides insights into the processes controlling marine-based ice sheet retreat. The over-deepened Ross Sea continental shelf is an ideal configuration for marine ice-sheet instability, and this region was thought to be one of the largest Antarctic contributors to post-LGM sea level rise. However, the chronology and pattern of retreat of the LGM ice sheet in the Ross Sea is largely constrained by coastal records along the Transantarctic Mountain front in the Western Ross Sea. Although these offer more reliable dating techniques than marine sediment cores, they may be influenced by local glaciers derived from East Antarctic outlet glaciers. Consequently, these coastal records may be ambiguous in the broader context of retreat in the central regions of the Ross Sea. However, previous studies have inferred that records in this region retreated in a north to south pattern, and was fed by ice sourced from the central Ross Sea – with the implication that broader ice sheet retreat in the central Ross Sea occurred as late as the mid Holocene. We present two lines of evidence that counter this established interpretation of the pattern of retreat in the Ross Sea: 1) a sedimentary facies succession and foraminifera-based radiocarbon chronology from within the Ross Sea embayment that indicates glacial retreat and open marine conditions to the east of Ross Island was already in place before 8.6 cal ka BP, at least 1 kyr earlier than indicated by terrestrial records in McMurdo Sound; and 2) a new multibeam swath bathymetry data that identifies well-preserved glacial features indicating thick (〉700m) marine-based ice derived from the East Antarctic Ice Sheet (EAIS) coastal outlet glaciers dominated the ice sheet input into the southwestern Ross Sea during the last phases of glaciation – and thus may have acted independent of any ice in the central Ross Sea embayment. Comparing these data to new modelling experiments, we hypothesize that marine-based ice sheet retreat was triggered by oceanic forcings along most of the Pacific Ocean coastline of Antarctica, but continued early Holocene retreat into the inner shelf region of the Ross Sea occurred primarily as a consequence of marine ice sheet instability. Keywords: Ross Sea, deglaciation, Last Glacial Maximum, Holocene
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
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  • 5
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    A high-resolution climate record spanning the past 17 000 years recovered from Lake Ohau, South Island, New Zealand (2019)
    Details
    Publication Date: 2019-10-24
    Description: A new annually resolved sedimentary record of Southern Hemisphere mid-latitude hydroclimate was recovered from Lake Ohau, South Island, New Zealand, in March 2016. The Lake Ohau Climate History (LOCH) project acquired cores from two sites (LOCH-1 and -2) that preserve sequences of laminated mud that accumulated since the lake formed similar to 17 000 years ago. Cores were recovered using a purpose-built barge and drilling system designed to recover soft sediment from thick sedimentary sequences in lake systems up to 150m deep. This system can be transported in two to three 40 ft long shipping containers and is suitable for use in a range of geographic locations. A comprehensive suite of data has been collected from the sedimentary sequence using state-of-the-art analytical equipment and techniques. These new observations of past environmental variability augment the historical instrumental record and are currently being integrated with regional climate and hydrological modelling studies to explore causes of variability in extreme/flood events over the past several millennia.
    Description: Published
    Description: 41-50
    Description: 4A. Oceanografia e clima
    Description: 5A. Paleoclima e ricerche polari
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    Antarctic marine ice-sheet retreat in the Ross Sea during the early Holocene (2016)
    GSA pubs
    In:  EPIC3Geology, GSA pubs, 44(1), pp. 7-10, ISSN: 1943-2682
    Details
    Publication Date: 2018-08-10
    Description: Geological constraints on the timing of retreat of the Last Glacial Maximum (LGM) Antarctic Ice Sheets provide critical insights into the processes controlling marine-based ice-sheet retreat. The over-deepened, landward-sloping bathymetry of Antarctica's continental shelves is an ideal configuration for marine ice-sheet instability, with the potential for past and future ice-sheet collapse and accelerated sea-level rise. However, the chronology of retreat of the LGM ice sheet in the Ross Sea is largely constrained by imprecise radiocarbon chronology of bulk marine sediments or by coastal records that offer more reliable dating techniques but which may be influenced by local piedmont glaciers derived from East Antarctic outlet glaciers. Consequently, these coastal records may be ambiguous in the broader context of retreat in the central regions of the Ross Sea. Here, we present a sedimentary facies succession and foraminifera-based radiocarbon chronology from within the Ross Sea embayment that indicates glacial retreat and open-marine conditions to the east of Ross Island before 8.6 cal. (calibrated) kyr B.P., at least 1 k.y. earlier than indicated by terrestrial records in McMurdo Sound. Comparing these data to new modeling experiments, we hypothesize that marine-based ice-sheet retreat was triggered by oceanic forcings along most of the Pacific Ocean coastline of Antarctica, but continued Holocene retreat into the inner shelf region of the Ross Sea occurred primarily as a consequence of bathymetric controls on marine ice-sheet instability.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 7
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    Holocene Marine-Based Ice Sheet Instability in the Ross Sea (2015)
    In:  EPIC3XII International Symposium on Antarctic Earth Sciences, Goa, India, 2015-07-13-2015-07-17
    Details
    Publication Date: 2018-08-10
    Description: Given the hypothesized instability of marine-based ice sheets to future warming, constraining the rate of retreat under past natural warming regimes can provide new insight into the mechanics of ice sheet retreat and their sensitivity to environmental change. However, the timing of this retreat in Antarctica is variably well-constrained. In part this is due to a paucity of suitable post-LGM records, but also due to the well-documented difficulties in reliably dating marine deposits with the 14C method around Antarctica due to a lack of suitable carbonate material. Most chronologies from the marine realm in the Ross Sea are largely dependent on Acid Insoluble Organic radiocarbon ages from bulk sediments that inherently overestimate the timing of glacial retreat ages due to pervasive reworking of older carbon on the continental shelves of the Antarctic. Here, we report a lithofacies-based retreat history from the ANDRILL Coulman High drill site in the Central Ross Embayment. This site was located within the paleo-drainage path of the Byrd Glacier, the largest East Antarctic Ice Sheet outlet glacier draining in to the Ross Sea at the LGM. Planktic and benthic formaniferal-based radiocarbon dates from a laminated-diatom- and icerafted debris-bearing glaciomarine mud constrain the retreat history of the Last Glacial Maximum (LGM) ice sheet in the Ross Embayment. During post-LGM retreat of the ice sheet margin in western Ross Sea, the calving line became ‗pinned‘ in the Ross Island region and the grounding line continued its retreat toward its present day location. This establishes that the modern-day calving line location of the Ross Ice Shelf was established by the Early Holocene, and that the ice sheet retreat was initiated in the Ross Sea prior to this time, but also continued through into the mid-Holocene. We examine our results in the context of oceanic drivers and marine instability mechanisms for the LGM retreat of the ice sheets in the Ross Embayment.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 8
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    Sensitivity of the West Antarctic Ice Sheet to +2 °C (SWAIS 2C) (2022)
    In:  EPIC3Scientific Drilling, 30, pp. 101-112, ISSN: 1816-3459
    Details
    Publication Date: 2022-03-14
    Description: The West Antarctic Ice Sheet (WAIS) presently holds enough ice to raise global sea level by 4.3 m if completely melted. The unknown response of the WAIS to future warming remains a significant challenge for numerical models in quantifying predictions of future sea level rise. Sea level rise is one of the clearest planet-wide signals of human-induced climate change. The Sensitivity of the West Antarctic Ice Sheet to a Warming of 2 ∘C (SWAIS 2C) Project aims to understand past and current drivers and thresholds of WAIS dynamics to improve projections of the rate and size of ice sheet changes under a range of elevated greenhouse gas levels in the atmosphere as well as the associated average global temperature scenarios to and beyond the +2 ∘C target of the Paris Climate Agreement. Despite efforts through previous land and ship-based drilling on and along the Antarctic margin, unequivocal evidence of major WAIS retreat or collapse and its causes has remained elusive. To evaluate and plan for the interdisciplinary scientific opportunities and engineering challenges that an International Continental Drilling Program (ICDP) project along the Siple coast near the grounding zone of the WAIS could offer (Fig. 1), researchers, engineers, and logistics providers representing 10 countries held a virtual workshop in October 2020. This international partnership comprised of geologists, glaciologists, oceanographers, geophysicists, microbiologists, climate and ice sheet modelers, and engineers outlined specific research objectives and logistical challenges associated with the recovery of Neogene and Quaternary geological records from the West Antarctic interior adjacent to the Kamb Ice Stream and at Crary Ice Rise. New geophysical surveys at these locations have identified drilling targets in which new drilling technologies will allow for the recovery of up to 200 m of sediments beneath the ice sheet. Sub-ice-shelf records have so far proven difficult to obtain but are critical to better constrain marine ice sheet sensitivity to past and future increases in global mean surface temperature up to 2 ∘C above pre-industrial levels. Thus, the scientific and technological advances developed through this program will enable us to test whether WAIS collapsed during past intervals of warmth and determine its sensitivity to a +2 ∘C global warming threshold (UNFCCC, 2015).
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
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    Neogene tectonic and climatic evolution of the Western Ross Sea, Antarctica — Chronology of events from the AND-1B drill hole (2012)
    In:  EPIC3Global and Planetary Change, 96-97, pp. 189-203, ISSN: 09218181
    Details
    Publication Date: 2018-08-10
    Description: Stratigraphic drilling from the McMurdo Ice Shelf in the 2006/2007 austral summer recovered a 1284.87 m sedimentary succession from beneath the sea floor. Key age data for the core include magnetic polarity stratigraphy for the entire succession, diatom biostratigraphy for the upper 600 m and 40Ar/39Ar ages for in-situ volcanic deposits as well as reworked volcanic clasts. A vertical seismic profile for the drill hole allows correlation between the drill hole and a regional seismic network and inference of age constraint by correlation with well‐dated regional volcanic events through direct recognition of interlayered volcanic deposits as well as by inference from flexural loading of pre‐existing strata. The combined age model implies relatively rapid (1 m/2–5 ky) accumulation of sediment punctuated by hiatuses, which account for approximately 50% of the record. Three of the longer hiatuses coincide with basin‐wide seismic reflectors and, along with two thick volcanic intervals, they subdivide the succession into seven chronostratigraphic intervals with characteristic facies: 1. The base of the cored succession (1275–1220 mbsf) comprises middle Miocene volcaniclastic sandstone dated at approx 13.5 Ma by several reworked volcanic clasts; 2. A late-Miocene sub-polar orbitally controlled glacial–interglacial succession (1220–760 mbsf) bounded by two unconformities correlated with basin‐wide reflectors associated with early development of the terror rift; 3. A late Miocene volcanigenic succession (760–596 mbsf) terminating with a ~1 my hiatus at 596.35 mbsf which spans the Miocene–Pliocene boundary and is not recognised in regional seismic data; 4. An early Pliocene obliquity-controlled alternating diamictite and diatomite glacial–interglacial succession (590–440 mbsf), separated from; 5. A late Pliocene obliquity-controlled alternating diamictite and diatomite glacial–interglacial succession (440–150 mbsf) by a 750 ky unconformity interpreted to represent a major sequence boundary at other locations; 6. An early Pleistocene interbedded volcanic, diamictite and diatomite succession (150–80 mbsf), and; 7. A late Pleistocene glacigene succession (80–0 mbsf) comprising diamictite dominated sedimentary cycles deposited in a polar environment.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
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    Skeletal density of Porites
    PANGAEA
    In:  Supplement to: Gagan, Michael K; Dunbar, Gavin B; Suzuki, Atsushi (2012): The effect of skeletal mass accumulation in Porites on coral Sr/Ca and d18O paleothermometry. Paleoceanography, 27(1), PA1203, https://doi.org/10.1029/2011PA002215
    Details
    Publication Date: 2023-05-12
    Description: Paleotemperature estimates based on coral Sr/Ca have not been widely accepted because the reconstructed glacial-Holocene shift in tropical sea-surface temperature (~4-6°C) is larger than that indicated by foraminiferal Mg/Ca (~2-4°C). We show that corals over-estimate changes in sea-surface temperature (SST) because their records are attenuated during skeletogenesis within the living tissue layer. To quantify this process, we microprofiled skeletal mass accumulation within the tissue layer of Porites from Australasian coral reefs and laboratory culturing experiments. The results show that the sensitivity of the Sr/Ca and d18O thermometers in Porites will be suppressed, variable, and dependent on the relationship between skeletal growth rate and mass accumulation within the tissue layer. Our findings help explain why d18O-SST sensitivities for Porites range from -0.08 per mil/°C to -0.22 per mil/°C and are always less than the value of -0.23 per mil/°C established for biogenic aragonite. Based on this observation, we recalibrated the coral Sr/Ca thermometer to determine a revised sensitivity of -0.084 mmol/mol/°C. After rescaling, most of the published Sr/Ca-SST estimates for the Indo-Pacific region for the last ~14,000 years (-7°C to +2°C relative to modern) fall within the 95% confidence envelope of the foraminiferal Mg/Ca-SST records. We conclude that two types of calibration scales are required for coral paleothermometry; an attenuated Porites-specific thermometer sensitivity for studies of seasonal to interannual change in SST and, importantly, the rescaled -0.084 mmol/mol/°C Sr/Ca sensitivity for studies of 20th-century trends and millennial-scale changes in mean SST. The calibration-scaling concept will apply to the development of transfer functions for all geochemical tracers in corals.
    Type: Dataset
    Format: application/zip, 2 datasets
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