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  • 1
    Publication Date: 2013-04-21
    Description: During the middle and late Eocene (∼48-34 Myr ago), the Earth's climate cooled1,2 and an ice sheet built up on Antarctica. The stepwise expansion of ice on Antarctica3,4induced crustal deformation and gravitational perturbations around the continent. Close to the ice sheet, sea level rose5,6despite an overall reduction in the mass of the ocean caused by the transfer of water to the ice sheet. Here we identify the crustal response to ice-sheet growth by forcing a glacial-hydro isostatic adjustment model7 with an Antarctic ice-sheet model. We find that the shelf areas around East Antarctica first shoaled as upper mantle material upwelled and a peripheral forebulge developed. The inner shelf subsequently subsided as lithosphere flexure extended outwards from the ice-sheet margins. Consequently the coasts experienced a progressive relative sea-level rise. Our analysis of sediment cores from the vicinity of the Antarctic ice sheet are in agreement with the spatial patterns of relative sea-level change indicated by our simulations. Our results are consistent with the suggestion8 that near-field processes such as local sea-level change influence the equilibrium state obtained by an icesheet grounding line.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 2
    Publication Date: 2018-10-22
    Description: An International Ocean Discovery Program (IODP) workshop was held at Sydney University, Australia, from 13 to 16 June 2017 and was attended by 97 scientists from 12 countries. The aim of the workshop was to investigate future drilling opportunities in the eastern Indian Ocean, southwestern Pacific Ocean, and the Indian and Pacific sectors of the Southern Ocean. The overlying regional sedimentary strata are underexplored relative to their Northern Hemisphere counterparts, and thus the role of the Southern Hemisphere in past global environmental change is poorly constrained. A total of 23 proposal ideas were discussed, with 12 of these deemed mature enough for active proposal development or awaiting scheduled site survey cruises. Of the remaining 11 proposals, key regions were identified where fundamental hypotheses are testable by drilling, but either site surveys are required or hypotheses need further development. Refinements are anticipated based upon regional IODP drilling in 2017/2018, analysis of recently collected site survey data, and the development of site survey proposals. We hope and expect that this workshop will lead to a new phase of scientific ocean drilling in the Australasian region in the early 2020s.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
    Format: application/pdf
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  • 3
    Publication Date: 2018-02-20
    Description: We examine ocean changes in response to changes in paleogeography from the Cretaceous to present in an intermediate complexity model and in the fully coupled CCSM3 model. Greenhouse gas concentrations are kept constant to allow a focus on effects arising from changing continental configurations. We find consistent and significant geography-related Cenozoic cooling arising from the opening of Southern Ocean (SO) gateways. Both models show significant deep ocean cooling arising from tectonic evolution alone. Simulations employing continental configurations associated with greenhouse climates, namely the Turonian and the Eocene simulations, systematically exhibit warm deep ocean temperatures at elevated pCO2 close to 10 °C. In contrast, continental configurations associated with (later) icehouse climates are associated with cooler deep ocean temperatures at identical pCO2, arising from a progressive strengthening of the Antarctic Circumpolar Current. This suggests that a component of the Cenozoic benthic cooling trend recorded in oxygen isotopes could arise directly from changes in continental configuration, and so be partially decoupled from the Cenozoic greenhouse gas history. In this paper we will present our model results against the background of an extensive review of previous work on ocean gateways and additional modelling results from several other global climate models.
    Type: Article , PeerReviewed
    Format: text
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  • 4
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , NonPeerReviewed
    Format: application/zip
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  • 5
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    PANGAEA
    In:  Supplement to: Bijl, Peter K; Schouten, Stefan; Sluijs, Appy; Reichart, Gert-Jan; Zachos, James C; Brinkhuis, Henk (2009): Early Palaeogene temperature evolution of the southwest Pacific Ocean. Nature, 461, 776-779, https://doi.org/10.1038/nature08399
    Publication Date: 2019-08-03
    Description: Relative to the present day, meridional temperature gradients in the Early Eocene age (~56-53 Myr ago) were unusually low, with slightly warmer equatorial regions (Pearson et al., 2007, doi:10.1130/G23175A.1 ) but with much warmer subtropical Arctic (Sluijs et al., 2008, doi:10.1029/2007PA001495) and mid-latitude (Sluijs et al., 2007, doi:10.1038/nature06400) climates. By the end of the Eocene epoch (~34 Myr ago), the first major Antarctic ice sheets had appeared (Zachos et al., 1992, doi:10.1130/0091-7613(1992)020〈0569:EOISEO〉2.3.CO;2; Barker et al., 2007, doi:10.1016/j.dsr2.2007.07.027), suggesting that major cooling had taken place. Yet the global transition into this icehouse climate remains poorly constrained, as only a few temperature records are available portraying the Cenozoic climatic evolution of the high southern latitudes. Here we present a uniquely continuous and chronostratigraphically well-calibrated TEX86 record of sea surface temperature (SST) from an ocean sediment core in the East Tasman Plateau (palaeolatitude ~65° S). We show that southwest Pacific SSTs rose above present-day tropical values (to ~34° C) during the Early Eocene age (~53 Myr ago) and had gradually decreased to about 21° C by the early Late Eocene age (~36 Myr ago). Our results imply that there was almost no latitudinal SST gradient between subequatorial and subpolar regions during the Early Eocene age (55-50 Myr ago). Thereafter, the latitudinal gradient markedly increased. In theory, if Eocene cooling was largely driven by a decrease in atmospheric greenhouse gas concentration Zachos et al. (2008, doi:10.1038/nature06588), additional processes are required to explain the relative stability of tropical SSTs given that there was more significant cooling at higher latitudes.
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 6
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    PANGAEA
    In:  Supplement to: Sluijs, Appy; Bijl, Peter K; Schouten, Stefan; Röhl, Ursula; Reichart, Gert-Jan; Brinkhuis, Henk (2011): Southern ocean warming, sea level and hydrological change during the Paleocene-Eocene thermal maximum. Climate of the Past, 7(1), 47-61, https://doi.org/10.5194/cp-7-47-2011
    Publication Date: 2019-08-03
    Description: A brief (~150 kyr) period of widespread global average surface warming marks the transition between the Paleocene and Eocene epochs, ~56 million years ago. This so-called "Paleocene-Eocene thermal maximum" (PETM) is associated with the massive injection of 13C-depleted carbon, reflected in a negative carbon isotope excursion (CIE). Biotic responses include a global abundance peak (acme) of the subtropical dinoflagellate Apectodinium. Here we identify the PETM in a marine sedimentary sequence deposited on the East Tasman Plateau at Ocean Drilling Program (ODP) Site 1172 and show, based on the organic paleothermometer TEX86, that southwest Pacific sea surface temperatures increased from ~26 °C to ~33°C during the PETM. Such temperatures before, during and after the PETM are 〉10 °C warmer than predicted by paleoclimate model simulations for this latitude. In part, this discrepancy may be explained by potential seasonal biases in the TEX86 proxy in polar oceans. Additionally, the data suggest that not only Arctic, but also Antarctic temperatures may be underestimated in simulations of ancient greenhouse climates by current generation fully coupled climate models. An early influx of abundant Apectodinium confirms that environmental change preceded the CIE on a global scale. Organic dinoflagellate cyst assemblages suggest a local decrease in the amount of river run off reaching the core site during the PETM, possibly in concert with eustatic rise. Moreover, the assemblages suggest changes in seasonality of the regional hydrological system and storm activity. Finally, significant variation in dinoflagellate cyst assemblages during the PETM indicates that southwest Pacific climates varied significantly over time scales of 103 - 104 years during this event, a finding comparable to similar studies of PETM successions from the New Jersey Shelf.
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 7
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    PANGAEA
    In:  Supplement to: Pross, Jörg; Contreras, Lineth; Bijl, Peter K; Greenwood, David R; Bohaty, Steven M; Schouten, Stefan; Bendle, James A; Röhl, Ursula; Tauxe, Lisa; Raine, J Ian; Huck, Claire E; van de Flierdt, Tina; Jamieson, Stewart S R; Stickley, Catherine E; van de Schootbrugge, Bas; Escutia Dotti, Carlota; Brinkhuis, Henk; IODP Expedition 318 Scientists (2012): Persistent near-tropical warmth on the Antarctic continent during the early Eocene epoch. Nature, 488(7409), 73-77, https://doi.org/10.1038/nature11300
    Publication Date: 2019-08-03
    Description: The warmest global climates of the past 65 million years occurred during the early Eocene epoch (about 55 to 48 million years ago), when the Equator-to-pole temperature gradients were much smaller than today (doi:10.1130/0091-7613(1995)023〈1044:ECCALT〉2.3.CO;2, doi:10.1038/nature08399) and atmospheric carbon dioxide levels were in excess of one thousand parts per million by volume (doi:10.1016/j.gca.2003.09.002, doi:10.1038/ngeo1186). Recently the early Eocene has received considerable interest because it may provide insight into the response of Earth's climate and biosphere to the high atmospheric carbon dioxide levels that are expected in the near future (doi:10.1007/s10584-011-0156-z) as a consequence of unabated anthropogenic carbon emissions (doi:10.1038/ngeo1186, doi:10.1038/nature06588). Climatic conditions of the early Eocene 'greenhouse world', however, are poorly constrained in critical regions, particularly Antarctica. Here we present a well-dated record of early Eocene climate on Antarctica from an ocean sediment core recovered off the Wilkes Land coast of East Antarctica. The information from biotic climate proxies (pollen and spores) and independent organic geochemical climate proxies (indices based on branched tetraether lipids) yields quantitative, seasonal temperature reconstructions for the early Eocene greenhouse world on Antarctica. We show that the climate in lowland settings along the Wilkes Land coast (at a palaeolatitude of about 70° south) supported the growth of highly diverse, near-tropical forests characterized by mesothermal to megathermal floral elements including palms and Bombacoideae. Notably, winters were extremely mild (warmer than 10 °C) and essentially frost-free despite polar darkness, which provides a critical new constraint for the validation of climate models and for understanding the response of high-latitude terrestrial ecosystems to increased carbon dioxide forcing.
    Type: Dataset
    Format: application/zip, 6 datasets
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  • 8
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    PANGAEA
    In:  Supplement to: Contreras, Lineth; Pross, Jörg; Bijl, Peter K; Koutsodendris, Andreas; Raine, J Ian; van de Schootbrugge, Bas; Brinkhuis, Henk (2013): Early to Middle Eocene vegetation dynamics at the Wilkes Land Margin (Antarctica). Review of Palaeobotany and Palynology, 197, 119-142, https://doi.org/10.1016/j.revpalbo.2013.05.009
    Publication Date: 2019-08-03
    Description: The early Eocene epoch was characterized by extreme global warmth, which in terrestrial settings was characterized by an expansion of near-tropical vegetation belts into the high latitudes. During the middle to late Eocene, global cooling caused the retreat of tropical vegetation to lower latitudes. In high-latitude settings, near-tropical vegetation was replaced by temperate floras. This floral change has recently been traced as far south as Antarctica, where along the Wilkes Land margin paratropical forests thrived during the early Eocene and temperate Nothofagus forests developed during the middle Eocene. Here we provide both qualitative and quantitative palynological data for this floral turnover based on a sporomorph record recovered at Integrated Ocean Drilling Program (IODP) Site U1356 off the Wilkes Land margin. Following the nearest living relative concept and based on a comparison with modern vegetation types, we examine the structure and diversity patterns of the Eocene vegetation along the Wilkes Land margin. Our results indicate that the early Eocene forests along the Wilkes Land margin were characterized by a diverse canopy composed of plants that today occur in tropical settings; their richness pattern was similar to that of present-day forests from New Caledonia. The middle Eocene forests were characterized by a canopy dominated by Nothofagus and exhibited richness patterns similar to modern Nothofagus forests from New Zealand.
    Type: Dataset
    Format: application/zip, 3 datasets
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  • 9
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    PANGAEA
    In:  Supplement to: Warnaar, Jeroen; Bijl, Peter K; Huber, Matthew; Sloan, Lisa; Brinkhuis, Henk; Röhl, Ursula; Sriver, Ryan; Visscher, Henk (2009): Orbitally forced climate changes in the Tasman sector during the Middle Eocene. Palaeogeography, Palaeoclimatology, Palaeoecology, 280(3-4), 361-370, https://doi.org/10.1016/j.palaeo.2009.06.023
    Publication Date: 2019-08-03
    Description: The influence of orbital precession on early Paleogene climate and ocean circulation patterns in the southeast Pacific region is investigated by combining environmental analyses of cyclic Middle Eocene sediments and palynomorph records recovered from ODP Hole 1172A on the East Tasman Plateau with climate model simulations. Integration of results indicates that in the marine realm, direct effects of precessional forcing are not pronounced, although increased precipitation/runoff could have enhanced dinoflagellate cyst production. On the southeast Australian continent, the most pronounced effects of precessional forcing were fluctuations in summer precipitation and temperature on the Antarctic Margin. These fluctuations resulted in vegetational changes, most notably in the distribution of Nothofagus (subgenus Brassospora). The climate model results suggest significant fluctuations in sea ice in the Ross Sea, notably during Austral summers. This is consistent with the influx of Antarctic heterotrophic dinoflagellates in the early part of the studied record. The data demonstrate a strong precessionally driven climate variability and thus support the concept that precessional forcing could have played a role in early Antarctic glaciation via changes in runoff and/or precipitation.
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 10
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    PANGAEA
    In:  Supplement to: Houben, Alexander J P; Bijl, Peter K; Pross, Jörg; Bohaty, Steven M; Passchier, Sandra; Stickley, Catherine E; Röhl, Ursula; Sugisaki, Saiko; Tauxe, Lisa; van de Flierdt, Tina; Olney, M; Sangiorgi, Francesca; Sluijs, Appy; Escutia Dotti, Carlota; Brinkhuis, Henk; Sawyer, Dale S (2013): Reorganization of Southern Ocean plankton ecosystem at the onset of Antarctic glaciation. Science, 340(6130), 341-344, https://doi.org/10.1126/science.1223646
    Publication Date: 2019-08-03
    Description: The circum-Antarctic Southern Ocean is an important region for global marine food webs and carbon cycling because of sea-ice formation and its unique plankton ecosystem. However, the mechanisms underlying the installation of this distinct ecosystem and the geological timing of its development remain unknown. Here, we show, on the basis of fossil marine dinoflagellate cyst records, that a major restructuring of the Southern Ocean plankton ecosystem occurred abruptly and concomitant with the first major Antarctic glaciation in the earliest Oligocene (~33.6 million years ago). This turnover marks a regime shift in zooplankton-phytoplankton interactions and community structure, which indicates the appearance of eutrophic and seasonally productive environments on the Antarctic margin. We conclude that earliest Oligocene cooling, ice-sheet expansion, and subsequent sea-ice formation were important drivers of biotic evolution in the Southern Ocean.
    Type: Dataset
    Format: application/zip, 5 datasets
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