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  • 1
    Publication Date: 2023-03-14
    Keywords: Barium/Calcium ratio; Carbon dioxide, partial pressure; Growth rate per area; Identification; Linear extension; Lithium/Calcium ratio; Magnesium/Calcium ratio; Magnesium/Lithium ratio; pH; pH, standard deviation; Salinity; Species; Temperature, water; Temperature, water, standard deviation; δ11B, borate; δ11B, carbonate; δ11B, standard deviation
    Type: Dataset
    Format: text/tab-separated-values, 708 data points
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  • 2
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    In:  Supplement to: Gutjahr, Marcus; Vance, Derek; Hoffmann, Dirk L; Hillenbrand, Claus-Dieter; Foster, Gavin L; Rae, James W B; Kuhn, Gerhard (2013): Structural limitations in deriving accurate U-series ages from calcitic cold-water corals contrast with robust coral radiocarbon and Mg/Ca systematics. Chemical Geology, 355, 69-87, https://doi.org/10.1016/j.chemgeo.2013.07.002
    Publication Date: 2023-05-12
    Description: Radiocarbon and uranium-thorium dating results are presented from a genus of calcitic Antarctic cold-water octocorals (family Coralliidae), which were collected from the Marie Byrd Seamounts in the Amundsen Sea (Pacific sector of the Southern Ocean) and which to date have not been investigated geochemically. The geochronological results are set in context with solution and laser ablation-based element/Ca ratios (Li, B, Mg, Mn, Sr, Ba, U, Th). Octocoral radiocarbon ages on living corals are in excellent agreement with modern ambient deep-water D14C, while multiple samples of individual fossil coral specimens yielded reproducible radiocarbon ages. Provided that local radiocarbon reservoir ages can be derived for a given time, fossil Amundsen Sea octocorals should be reliably dateable by means of radiocarbon. In contrast to the encouraging radiocarbon findings, the uranium-series data are more difficult to interpret. The uranium concentration of these calcitic octocorals is an order of magnitude lower than in the aragonitic hexacorals that are conventionally used for geochronological investigations. While modern and Late Holocene octocorals yield initial d234U in good agreement with modern seawater, our results reveal preferential inward diffusion of dissolved alpha-recoiled 234U and its impact on fossil coral d234U. Besides alpha-recoil related 234U diffusion, high-resolution sampling of two fossil octocorals further demonstrates that diagenetic uranium mobility has offset apparent coral U-series ages. Combined with the preferential alpha-recoil 234U diffusion, this process has prevented fossil octocorals from preserving a closed system U-series calendar age for longer than a few thousand years. Moreover, several corals investigated contain significant initial thorium, which cannot be adequately corrected for because of an apparently variable initial 232Th/230Th. Our results demonstrate that calcitic cold-water corals are unsuitable for reliable U-series dating. Mg/Ca ratios within single octocoral specimens are internally strikingly homogeneous, and appear promising in terms of their response to ambient temperature. Magnesium/lithium ratios are significantly higher than usually observed in other deep marine calcifiers and for many of our studied corals are remarkably close to seawater compositions. Although this family of octocorals is unsuitable for glacial deep-water D14C reconstructions, our findings highlight some important differences between hexacoral (aragonitic) and octocoral (calcitic) biomineralisation. Calcitic octocorals could still be useful for trace element and some isotopic studies, such as reconstruction of ambient deep water neodymium isotope composition or pH, via boron isotopic measurements.
    Keywords: AWI_Paleo; Paleoenvironmental Reconstructions from Marine Sediments @ AWI
    Type: Dataset
    Format: application/zip, 3 datasets
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  • 3
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    In:  Supplement to: Crocket, Kirsty C; Vance, Derek; Foster, Gavin L; Richards, David A; Tranter, D J (2012): Continental weathering fluxes during the last glacial/interglacial cycle: insights from the marine sedimentary Pb isotope record at Orphan Knoll, NW Atlantic. Quaternary Science Reviews, 38, 89-99, https://doi.org/10.1016/j.quascirev.2012.02.004
    Publication Date: 2023-05-12
    Description: Regional weathering intensity must have changed dramatically at high latitudes during the Quaternary as a consequence of repeated continental glaciation. Investigation of these glacial/interglacial changes at high temporal resolution is possible with the recent development of Pb isotopes in FeMn oxyhydroxide phases as a proxy for region-specific weathering intensity, where increases in the radiogenic component are thought to correspond to increased continental weathering fluxes. Here we present a Pb isotope record sourced from the FeMn oxyhydroxide fraction in marine sediments from IODP Sites U1302/3 on Orphan Knoll (~3500 mbsl, NW Atlantic), spanning the last 37 ka. Located at the eastern edge of the Laurentide Ice Sheet (LIS), Site U1302/3 is well-placed to monitor changes in weathering intensity associated with LIS glacial history. Overall, the data show a close correspondence to local surface water d18O, with least radiogenic values during times of heavy d18O (glacial maximum) and most radiogenic values during times of light d18O (Holocene). This supports the prediction that weathering intensity in glaciated regions of the North Atlantic correlates with the exposure age of glacial debris. Superimposed on these background trends are extreme radiogenic excursions (e.g. variation in 206Pb/204Pb from ~19.2-21.0) contemporaneous with Heinrich events and the Younger Dryas. These data are substantially more radiogenic than existing records from the NW Atlantic, and most likely represent episodes of exceptionally high inputs of pre-formed FeMn oxyhydroxides during drainage of the LIS. Due to its extreme isotope composition, at least in the NW Atlantic region, Pb would appear to be a good proxy for the fluxes of weathered continental material and perhaps, by inference, nutrients to the surface ocean
    Keywords: Integrated Ocean Drilling Program / International Ocean Discovery Program; IODP
    Type: Dataset
    Format: application/zip, 5 datasets
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  • 4
    Publication Date: 2023-01-13
    Description: The geochemical measurements within the long-lived, crustose coralline red alga Clathromorphum compactum in calibration experiments, and the environmental conditions selected for the controlled laboratory aquaria.
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 5
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    In:  Supplement to: Rae, James W B; Sarnthein, Michael; Foster, Gavin L; Ridgwell, Andy; Grootes, Pieter Meiert; Elliott, Tim (2014): Deep water formation in the North Pacific and deglacial CO2 rise. Paleoceanography, 29(6), 645-667, https://doi.org/10.1002/2013PA002570
    Publication Date: 2023-01-13
    Description: Deep water formation in the North Atlantic and Southern Ocean is widely thought to influence deglacial CO2 rise and climate change; here we suggest that deep water formation in the North Pacific may also play an important role. We present paired radiocarbon and boron isotope data from foraminifera from sediment core MD02-2489 at 3640 m in the North East Pacific. These show a pronounced excursion during Heinrich Stadial 1, with benthic-planktic radiocarbon offsets dropping to ~350 years, accompanied by a decrease in benthic d11B. We suggest this is driven by the onset of deep convection in the North Pacific, which mixes young shallow waters to depth, old deep waters to the surface, and low-pH water from intermediate depths into the deep ocean. This deep water formation event was likely driven by an increase in surface salinity, due to subdued atmospheric/monsoonal freshwater flux during Heinrich Stadial 1. The ability of North Pacific Deep Water (NPDW) formation to explain the excursions seen in our data is demonstrated in a series of experiments with an intermediate complexity Earth system model. These experiments also show that breakdown of stratification in the North Pacific leads to a rapid ~30 ppm increase in atmospheric CO2, along with decreases in atmospheric d13C and D14C, consistent with observations of the early deglaciation. Our inference of deep water formation is based mainly on results from a single sediment core, and our boron isotope data are unavoidably sparse in the key HS1 interval, so this hypothesis merits further testing. However we note that there is independent support for breakdown of stratification in shallower waters during this period, including a minimum in d15N, younging in intermediate water 14C, and regional warming. We also re-evaluate deglacial changes in North Pacific productivity and carbonate preservation in light of our new data, and suggest that the regional pulse of export production observed during the Bølling-Allerød is promoted by relatively stratified conditions, with increased light availability and a shallow, potent nutricline. Overall, our work highlights the potential of NPDW formation to play a significant and hitherto unrealized role in deglacial climate change and CO2 rise.
    Type: Dataset
    Format: application/zip, 7 datasets
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  • 6
    Publication Date: 2023-01-30
    Description: Atmospheric dust is a primary source of iron (Fe) to the open ocean, and its flux is particularly important in the high nutrient, low chlorophyll (HNLC) Southern Ocean where Fe currently limits productivity. Alleviation of this Fe limitation in the Subantarctic Zone of the Atlantic by increased dust-borne Fe supply during glacial periods has been shown to increase primary productivity. However, previous work has found no such increase in productivity in the Pacific sector. In order to constrain the relative importance of Southern Ocean Fe fertilization on glacial-interglacial carbon cycles, records of dust fluxes outside of the Atlantic sector of the Southern Ocean at the Last Glacial Maximum (LGM) are required. Here we use grain size and U-series analyses to reconstruct lithogenic and CaCO3 fluxes, and Nd, Sr and Pb isotopes to ascertain the provenance of terrigenous material delivered to four deep-water cores in the SW Pacific Ocean over the last ~30kyr. We find evidence for an increase in the relative proportion of fine-grained (0.5-12 µm) terrigenous sediment and higher detrital fluxes during the LGM compared to the Holocene. The provenance of the LGM dust varied spatially, with an older, more "continental" signature (low εNd, high 87Sr/86Sr) sourced from Australia in the northern cores, and a younger, more volcanogenic source in the southern cores (high εNd, low 87Sr/86Sr), likely sourced locally from New Zealand. Given this increase in lithogenic flux to the HNLC subantarctic Pacific Southern Ocean during the LGM, factors besides Fe-supply must have regulated the biological productivity here.
    Keywords: 232Th-fluxes; Dust provenance; grain size analysis; Last Glacial Maximum; Nd; Pb isotopes; Sr; Subantarctic zone; SW Pacific
    Type: Dataset
    Format: application/zip, 6 datasets
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  • 7
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    In:  Supplement to: Lang, David C; Bailey, Ian; Wilson, Paul A; Chalk, Thomas B; Foster, Gavin L; Gutjahr, Marcus (2016): Incursions of southern-sourced water into the deep North Atlantic during late Pliocene glacial intensification. Nature Geoscience, 9(5), 375-379, https://doi.org/10.1038/ngeo2688
    Publication Date: 2023-02-24
    Description: The circulation and internal structure of the oceans exert a strong influence on Earth's climate because they control latitudinal heat transport and the segregation of carbon between the atmosphere and the abyss (Sigman et al., 2010, doi:10.1038/nature09149). Circulation change, particularly in the Atlantic Ocean, is widely suggested (Bartoli et al., 2005, doi:10.1016/j.epsl.2005.06.020; Haug and Tiedemann, 1998, doi:10.1038/31447; Woodard et al., 2014, doi:10.1126/science.1255586; McKay et al., 2012, doi:10.1073/pnas.1112248109) to have been instrumental in the intensification of Northern Hemisphere glaciation when large ice sheets first developed on North America and Eurasia during the late Pliocene, approximately 2.7 million years ago (Bailey et al., 2013, doi:10.1016/j.quascirev.2013.06.004). Yet the mechanistic link and cause/effect relationship between ocean circulation and glaciation are debated. Here we present new records of North Atlantic Ocean structure using the carbon and neodymium isotopic composition of marine sediments recording deep water for both the Last Glacial to Holocene (35-5 thousand years ago) and the late Pliocene to earliest Pleistocene (3.3-2.4 million years ago). Our data show no secular change. Instead we document major southern-sourced water incursions into the deep North Atlantic during prominent glacials from 2.7 million years ago. Our results suggest that Atlantic circulation acts as a positive feedback rather than as an underlying cause of late Pliocene Northern Hemisphere glaciation. We propose that, once surface Southern Ocean stratification (Sigman, et al., 2004, doi:10.1038/nature02357) and/or extensive sea-ice cover (McKay et al., 2012, doi:10.1073/pnas.1112248109) was established, cold-stage expansions of southern-sourced water such as those documented here enhanced carbon dioxide storage in the deep ocean, helping to increase the amplitude of glacial cycles.
    Keywords: Integrated Ocean Drilling Program / International Ocean Discovery Program; IODP
    Type: Dataset
    Format: application/zip, 5 datasets
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  • 8
    Publication Date: 2023-05-12
    Keywords: 303-U1302; AGE; COMPCORE; Composite Core; DEPTH, sediment/rock; DSDP/ODP/IODP sample designation; Exp303; Integrated Ocean Drilling Program / International Ocean Discovery Program; IODP; Joides Resolution; Lead; Lead-206/Lead-204 ratio; Lead-207/Lead-204 ratio; Lead-207/Lead-206 ratio; Lead-208/Lead-204 ratio; Lead-208/Lead-206 ratio; North Atlantic Climate 1; Northwest Atlantic; Sample code/label
    Type: Dataset
    Format: text/tab-separated-values, 342 data points
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  • 9
    Publication Date: 2023-05-12
    Keywords: 303-U1302; Age model; Calculated; COMPCORE; Composite Core; Datum level; Depth, composite bottom; Depth, composite top; DEPTH, sediment/rock; Exp303; Integrated Ocean Drilling Program / International Ocean Discovery Program; IODP; Joides Resolution; North Atlantic Climate 1; Northwest Atlantic; Sedimentation rate
    Type: Dataset
    Format: text/tab-separated-values, 25 data points
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  • 10
    Publication Date: 2023-05-12
    Keywords: 303-U1302; AGE; COMPCORE; Composite Core; DEPTH, sediment/rock; Exp303; Integrated Ocean Drilling Program / International Ocean Discovery Program; IODP; Joides Resolution; North Atlantic Climate 1; Northwest Atlantic; Sample comment; Strontium; Strontium-87/Strontium-86 ratio; Strontium-87/Strontium-86 ratio, error
    Type: Dataset
    Format: text/tab-separated-values, 94 data points
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