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  • Open Access English
    Authors: 
    Van Audenhaege, Loïc; Broad, Emmeline; Hendry, Katharine R; Huvenne, Veerle A I;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: EC | iAtlantic (818123), EC | ICY-LAB (678371)

    We used a multibeam echosounder (Reson7125) front-mounted onto the ROV Isis (Dive D333, DY081 expedition) to map the terrain of a vertical feature marking the edge of a deep-sea glacial trough (Labrador Sea, [63°51.9'N, 53°16.9'W, depth: 650 to 800 m]). After correction of the ROV navigation (i.e. merging of USBL and DVL), bathymetry [m] and backscatter [nominal unit] were extracted at a resolution of 0.3 m and different terrain descriptors were computed: Slope, Bathymetric Position Index (BPI), Terrain Ruggedness Index, Roughness, Mean and Gaussian curvatures and orientations (Northness and Eastness), at scales of 0.9, 3 and 9 m. Using a Principal Component Analysis (PCA), the terrain descriptors enabled to retrieve 4 terrain clusters and their associated confusion index, to investigate the spatial heterogeneity of the terrain. This approach also underlined the presence of geomorphic features in the wall terrain. The extraction of the backscatter intensity for the first time considering vertical terrains, opens space for further acquisition and processing development. Using photographs collected by the ROV Isis (Dive D334, DY081 expedition), epibenthic fauna was annotated. Each image was linked to a terrain cluster in the 3D space and pooled into 20-m² bins of images. A Bray-Curtis dissimilarity matrix was constructed from morphospecies abundances. This enabled to test for differences of assemblage composition among clusters. Few species appeared more abundant in particular clusters such as L. pertusa in high-roughness cluster. However, nMDS suggested differences in assemblage composition but these dissimilarities were not strongly delineated. Whereas the design of this study may have limited distinctive differences among assemblages, this shows the potential of this cost-effective method of top-down habitat mapping to be applied in undersampled benthic habitat in order to provide a priori knwoledge for defining appropriate sampling design.

  • Open Access English
    Authors: 
    Schlolaut, Gordon; Brauer, Achim; Nakagawa, Takeshi; Lamb, Henry F; Tyler, Jonathan J; Staff, Richard A; Marshall, Michael H; Ramsey, Christopher Bronk; Bryant, Charlotte L; Tarasov, Pavel E;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: UKRI | Lake Suigetsu varved sedi... (NE/F003048/1), UKRI | Pan-hemispheric synchrony... (NE/D000289/1)

    The Younger Dryas Stadial (YDS) was an episode of northern hemispheric cooling which occurred within the Last Glacial Interglacial Transition (LGIT). A major driver for the YDS climate was a weakening of the Atlantic Meridional Overturning Circulation (AMOC). It has been inferred that the AMOC began to strengthen mid-YDS, producing a bipartite structure of the YDS in records from continental Europe. These records imply that the polar front and westerlies shifted northward, producing a warmer second phase of the YDS in Europe. Here we present multi-proxy data from the sediments of Lake Suigetsu (Japan), as evidence that a related bi-partition of the YDS also occurred in East Asia. Besides showing for the first time that the bi-partition was not limited to the North Atlantic/European region, the data also imply a climatic dipole between Europe and East Asia since the cold-warm characteristics are reversed at Lake Suigetsu. We suggest that changes in eastward moisture transport from the North Atlantic are the primary mechanism by which the teleconnection can be explained.

  • Open Access English
    Authors: 
    Felis, Thomas; McGregor, Helen V; Linsley, Braddock K; Tudhope, Alexander W; Gagan, Michael K; Suzuki, Atsushi; Inoue, Mayuri; Thomas, Alexander L; Esat, Tezer M; Thompson, William G; +5 more
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: UKRI | Sea level and climate cha... (NE/H014268/1), UKRI | The timing and amplitude ... (NE/H014136/1)

    Tropical south-western Pacific temperatures are of vital importance to the Great Barrier Reef (GBR), but the role of sea surface temperatures (SSTs) in the growth of the GBR since the Last Glacial Maximum remains largely unknown. Here we present records of Sr/Ca and d18O for Last Glacial Maximum and deglacial corals that show a considerably steeper meridional SST gradient than the present day in the central GBR. We find a 1-2 °C larger temperature decrease between 17° and 20°S about 20,000 to 13,000 years ago. The result is best explained by the northward expansion of cooler subtropical waters due to a weakening of the South Pacific gyre and East Australian Current. Our findings indicate that the GBR experienced substantial meridional temperature change during the last deglaciation, and serve to explain anomalous deglacial drying of northeastern Australia. Overall, the GBR developed through significant SST change and may be more resilient than previously thought.

  • Open Access English
    Authors: 
    Roberts, Jenny; Gottschalk, Julia; Skinner, Luke C; Peck, Victoria L; Kender, Sev; Elderfield, Henry; Waelbroeck, Claire; Vázquez Riveiros, Natalia; Hodell, David A;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: EC | ACCLIMATE (339108), UKRI | The bi-polar seesaw and C... (NE/J010545/1), EC | NEWLOG (267931)

    Explanations of the glacial-interglacial variations in atmospheric pCO2 invoke a significant role for the deep ocean in the storage of CO2. Deep-ocean density stratification has been proposed as a mechanism to promote the storage of CO2 in the deep ocean during glacial times. A wealth of proxy data supports the presence of a "chemical divide" between intermediate and deep water in the glacial Atlantic Ocean, which indirectly points to an increase in deep-ocean density stratification. However, direct observational evidence of changes in the primary controls of ocean density stratification, i.e., temperature and salinity, remain scarce. Here, we use Mg/Ca-derived seawater temperature and salinity estimates determined from temperature-corrected d18O measurements on the benthic foraminifer Uvigerina spp. from deep and intermediate water-depth marine sediment cores to reconstruct the changes in density of sub-Antarctic South Atlantic water masses over the last deglaciation (i.e., 22-2 ka before present). We find that a major breakdown in the physical density stratification significantly lags the breakdown of the deep-intermediate chemical divide, as indicated by the chemical tracers of benthic foraminifer d13C and foraminifer/coral 14C. Our results indicate that chemical destratification likely resulted in the first rise in atmospheric pCO2, whereas the density destratification of the deep South Atlantic lags the second rise in atmospheric pCO2 during the late deglacial period. Our findings emphasize that the physical and chemical destratification of the ocean are not as tightly coupled as generally assumed.

  • Open Access English
    Authors: 
    Griffiths, James D; Barker, Stephen; Hendry, Katharine R; Thornalley, David JR; van de Flierdt, Tina; Hall, Ian R; Anderson, Robert F;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NSF | Testing the Silicic Acid ... (1029986), UKRI | Changes in ocean circulat... (NE/F002734/1)

    Antarctic Intermediate Water (AAIW) and Subantarctic Mode Water (SAMW) are the main conduits for the supply of dissolved silicon (silicic acid) from the deep Southern Ocean (SO) to the low-latitude surface ocean and therefore have an important control on low-latitude diatom productivity. Enhanced supply of silicic acid by AAIW (and SAMW) during glacial periods may have enabled tropical diatoms to outcompete carbonate-producing phytoplankton, decreasing the relative export of inorganic to organic carbon to the deep ocean and lowering atmospheric pCO2. This mechanism is known as the "silicic acid leakage hypothesis" (SALH). Here we present records of neodymium and silicon isotopes from the western tropical Atlantic that provide the first direct evidence of increased silicic acid leakage from the Southern Ocean to the tropical Atlantic within AAIW during glacial Marine Isotope Stage 4 (~60-70 ka). This leakage was approximately coeval with enhanced diatom export in the NW Atlantic and across the eastern equatorial Atlantic and provides support for the SALH as a contributor to CO2 drawdown during full glacial development.

  • Open Access English
    Authors: 
    De Schepper, Stijn; Ray, Jessica L; Skaar, Katrine S; Sadatzki, Henrik; Ijaz, Umer Zeeshan; Stein, Ruediger; Larsen, Aud;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: UKRI | Undestanding microbial co... (NE/L011956/1), EC | ICE2ICE (610055), EC | AGENSI (818449)

    At Site GS15-198-38, Greenland Sea, we analysed the surface sample (from a multicore) and eight Late Quaternary samples from a Calypso core. The age model for the Calypso core GS15-198-38CC is based on seven AMS 14C ages down to 345 cm, and a 5-cm resolution N. pachyderma sinistral isotope stratigraphy (1) below that level. We analysed the palynology, generated organic biomarker data (including IP25, sterols) and performed quantitative PCR (droplet digital PCR, ddPCR) of the sympagic dinoflagellate Polarella glacialis. The main funding for this project came from:Research Council of Norway project 268062 (Environmental ancient DNA as proxy for sea ice reconstructions - aDNAPROX)Research Council of Norway project 273455/E10 (KLIMAFORSK mobility) Additional funding came from:Bjerknes Centre for Climate ResearchNatural Environment Research Council (NERC) Independent Research Fellowship NE/L011956/1Lord Kelvin Adam Smith Leadership Fellowship (University of Glasgow)European Research Council under the European Community's Seventh Framework Program (FP7/2007-2013) / ERC grant agreement 610055 as part of the ice2ice project

  • Open Access English
    Authors: 
    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; +6 more
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: EC | UNPACK CLIMATE (230828), UKRI | Antarctic Deep Water Circ... (NE/I006257/1), NSF | Magnetostratigraphy and R... (1058858), UKRI | Antarctic weathering and ... (NE/J019801/1), UKRI | FEC for sailing participa... (NE/H025162/1), UKRI | FEC Recovery for Shipboar... (NE/H020098/1), EC | DINOPRO (259627), NSF | The Stratigraphic Express... (1245283), NSF | RAPID: Collaborative Rese... (1054497)

    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.

  • Open Access English
    Authors: 
    Hendry, Katharine R;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: EC | ICY-LAB (678371)

    DY081 was the first fieldwork component of a European Research Council funded project, ICY-LAB, led by Dr. K. Hendry from the University of Bristol to study nutrient cycling in the North Atlantic. This data release contains seawater bottle data collected during DY081 by standard CTD rosette, remotely operated vehicle and Tow fish, together with ancillary, processed sensor data at the bottle opening depths. Four sites of interest were surveyed: Orphan Knoll off the coast of Newfoundland, and Nuuk, Nasrsaq, and Cape Farewell off southwest Greenland. Description of the data available is given in the Data Documentation file (see Further details).

  • Open Access English
    Authors: 
    Ng, Hong Chin; Cassarino, Lucie; Pickering, Rebecca A; Woodward, E Malcolm S; Hammond, Samantha J; Hendry, Katharine R;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: EC | ICY-LAB (678371)

    The dataset contains pore water and core incubation silicic acid concentration and isotope measurements, sponge silicon isotope measurements, and pore water major and trace elemental concentrations obtained from seven sediment cores collected from the Greenland margin and the Labrador Sea. The samples were collected as part of the European Research Council project ICY-LAB (ERC-2015-STG grant agreement number 678371).

  • Open Access English
    Authors: 
    Rush, Darci; Talbot, Helen M; van der Meer, Marcel T J; Hopmans, Ellen C; Douglas, Ben; Sinninghe Damsté, Jaap S;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NWO | Perturbations of System E... (2300181601), UKRI | Biohopanoid markers as tr... (NE/E017088/1), EC | AMOPROX (258734)

    The eastern Mediterranean Sea sedimentary record is characterised by intervals of organic rich sediment (sapropels), indicating periods of severe anoxia triggered by astronomical forcing. It has been hypothesized that nitrogen fixation was crucial in injecting the Mediterranean Sea with bioavailable nitrogen (N) during sapropel events. However, the evolution of the N biogeochemical cycle of sapropels is poorly understood. For example, the role of the complementary removal reaction, anaerobic ammonium oxidation (anammox), has not been investigated because the traditional lipid biomarkers for anammox, ladderane fatty acids, are not stable over long periods in the sedimentary record. The recent development of an alternative lipid biomarker for anammox (bacteriohopanetetrol stereoisomer; BHT isomer) allowed for the investigation of anammox during sapropel deposition in this marginal sea. We present here the first application of a lipid biomarker for N removal throughout the progression (e.g. formation, propagation, and termination) of basin-wide anoxic events. In this study, BHT isomer and ladderanes were analysed in sapropel records taken from three Eastern Mediterranean sediment cores, spanning the most recent (S1) to Pliocene sapropels. Ladderanes were rapidly degraded in sediments, as recently as the S5 sapropel (ca. 125 ka). BHT isomer, however, was present in all sapropel sediments, as far back as the Pliocene (2.97 Ma), and clearly showed the response of anammox bacteria to marine water column redox shifts in high-resolution records. Two different N removal scenarios were observed in Mediterranean sapropels. During S5, anammox experienced Black Sea-like water column conditions, with the peak of BHT isomer coinciding with the core of the sapropel. Under the alternative scenario observed in the Pliocene sapropel, the anammox biomarker peaked at onset and termination of said sapropel, which may indicate sulphide inhibition of anammox during the core of sapropel deposition. This study shows the use of BHT isomer as a biomarker for anammox in the marine sediment record and highlights its potential in reconstructing anammox during past anoxic events that are too old for ladderanes to be applied (e.g. the history of oxygen minimum zone expansion and oceanic anoxic events).

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