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72 Research products, page 1 of 8

  • European Marine Science
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  • Aurora Universities Network

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  • Open Access English
    Authors: 
    Romero-Alvarez, Johana; Lupaşcu, Aurelia; Lowe, Douglas; Badia, Alba; Acher-Nicholls, Scott; Dorling, Steve R.; Reeves, Claire E.; Butler, Tim;
    Project: EC | ASIBIA (616938)

    Tropospheric ozone (O3) concentrations depend on a combination of hemispheric, regional, and local-scale processes. Estimates of how much O3 is produced locally vs. transported from further afield are essential in air quality management and regulatory policies. Here, a tagged-ozone mechanism within the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) is used to quantify the contributions to surface O3 in the UK from anthropogenic nitrogen oxide (NOx) emissions from inside and outside the UK during May–August 2015. The contribution of the different source regions to three regulatory O3 metrics is also examined. It is shown that model simulations predict the concentration and spatial distribution of surface O3 with a domain-wide mean bias of −3.7 ppbv. Anthropogenic NOx emissions from the UK and Europe account for 13 % and 16 %, respectively, of the monthly mean surface O3 in the UK, as the majority (71 %) of O3 originates from the hemispheric background. Hemispheric O3 contributes the most to concentrations in the north and the west of the UK with peaks in May, whereas European and UK contributions are most significant in the east, south-east, and London, i.e. the UK's most populated areas, intensifying towards June and July. Moreover, O3 from European sources is generally transported to the UK rather than produced in situ. It is demonstrated that more stringent emission controls over continental Europe, particularly in western Europe, would be necessary to improve the health-related metric MDA8 O3 above 50 and 60 ppbv. Emission controls over larger areas, such as the Northern Hemisphere, are instead required to lessen the impacts on ecosystems as quantified by the AOT40 metric.

  • Open Access English
    Authors: 
    Wu, Jiawang; Liu, Zhifei; Michard, Annie; Tachikawa, Kazuyo; Filippidi, Amalia; He, Zhiwei; Hennekam, Rick; Yang, Shouye; Davies, Gareth R; de Lange, Gert J;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    Here we present the data of a sequential extraction scheme, which aims to evaluate the effect of barite-bound Sr in the residual fraction after decarbonation. The investigation is done with pertinent examples for Mediterranean sediments, focusing on the most-recent sapropel S1 interval. A total of 130 samples were taken from 10 cores in the eastern Mediterranean Sea (EMS) and 1 core in the western Mediterranean Sea. This selection represents a geographic and bathymetric coverage of the EMS and permits the basin-wide comparison between organic-rich and -lean sediments. After decarbonation using 1 M HCl solution, the residual sediments were subject to NH4Cl extraction (2 M, pH 7), known to selectively dissolve barite. Our results demonstrate the presence of Sr-bearing barite after traditional carbonate removal and its effect on the derived “detrital” Sr signature, with important implications for detrital provenance studies.

  • Other research product . Collection . Other ORP type . 2021
    Open Access English
    Authors: 
    van der Does, Michèlle; Wengler, Marc; Lamy, Frank; Martínez-García, Alfredo; Jaccard, Samuel L; Kuhn, Gerhard; Lanny, Verena; Stuut, Jan-Berend W; Winckler, Gisela;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    This dataset describes dust particle size of two marine sediment records in the Southern Ocean. The first record is South-Pacific core PS75/056-1 (55.16°S, 114.78°W; at 3581m water depth), recovered during R/V Polarstern expedition ANT-XXVI/2, PS75 (Gersonde, 2011). Samples from 0.07-9.93 m core depth were analysed (N=183), and grain sizes were analysed with the laser particle sizer Beckmann Coulter LS13 320 at NIOZ, The Netherlands. This record spans the last ~260 kyr. The second sediment record is ODP Site 1090 (42.91°S, 8.90°E, at 3702m water depth), recovered during the Ocean Drilling Program Leg 177 expedition (Gersonde et al., 1999). Samples from 0.00-4.84 m were analysed (N=333), and grain sizes for ODP Site 1090 were analysed with the laser particle sizer Malvern Mastersizer 2000 at ETH Zurich, Switzerland. This record spans the last ~160 kyr. For both records, grain-size analyses were performed on the isolated terrigenous fraction, after the biogenic components (organics, carbonates and biogenic opals) were removed. In addition, different size fractions were determined, and the mean grain sizes of four size fractions were calculated using the program GRADISTAT (Blott & Pye, 2001).

  • Other research product . Collection . Other ORP type . 2020
    English
    Authors: 
    Salvatteci, Renato;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    Here we present data of multiple types of fish debris in a composite record covering the last 25 kyr BP. The fish debris include fish scales, vertebrae and other bones. We also include 4 preservation indices, total organic carbon and carbonate fluxes.

  • Open Access English
    Authors: 
    Mischke, Steffen; Lai, Zhongping; Aichner, Bernhard; Heinecke, Liv; Makhmudov, Zafar; Kuessner, Marie L; Herzschuh, Ulrike;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    Lake Karakul in the eastern Pamirs is a large and closed-basin lake in a partly glaciated catchment. Two parallel sediment cores were collected from 12 m water depth. The cores were correlated using XRF analysis and the composite core of 12.26 m length represents continuous accumulation of sediments in the lake basin since 31 ka. To establish an age-model, radiocarbon dating of 24 samples (aquatic plant remains and bulk sediments) derived from all cores, and OSL dating of 10 sediment slices (8 - 12 cm) derived from core KK12-2 has been conducted. The age results of the two methods are generally in agreement. The lake reservoir effect (1386 years) was determined by dating of living aquatic plants and remained relatively constant over the length of the record. High sediment accumulation rates (SARs) were recorded before 23 ka and after 6.5 ka and interpreted to indicate relatively low lake levels. In contrast, low SARs between 23 and 6.5 ka suggest higher lake levels. The sediment cores from Lake Karakul represent an important climate archive with robust chronology for the last glacial-interglacial cycle from Central Asia.

  • Open Access English
    Authors: 
    Bar, Marijke W.; Ullgren, Jenny E.; Thunnell, Robert C.; Wakeham, Stuart G.; Brummer, Geert-Jan A.; Stuut, Jan-Berend W.; Sinninghe Damsté, Jaap S.; Schouten, Stefan;
    Project: EC | DUSTTRAFFIC (311152), EC | DIOLS (339206), NWO | TRAFFIC: Transatlantic fl... (2300175166), NWO | Perturbations of System E... (2300181601)

    In this study we analyzed sediment trap time series from five tropical sites to assess seasonal variations in concentrations and fluxes of long-chain diols (LCDs) and associated proxies with emphasis on the long-chain diol index (LDI) temperature proxy. For the tropical Atlantic, we observe that generally less than 2 % of LCDs settling from the water column are preserved in the sediment. The Atlantic and Mozambique Channel traps reveal minimal seasonal variations in the LDI, similar to the two other lipid-based temperature proxies TEX86 and U37K′. In addition, annual mean LDI-derived temperatures are in good agreement with the annual mean satellite-derived sea surface temperatures (SSTs). In contrast, the LDI in the Cariaco Basin shows larger seasonal variation, as do the TEX86 and U37K′. Here, the LDI underestimates SST during the warmest months, which is possibly due to summer stratification and the habitat depth of the diol producers deepening to around 20–30 m. Surface sediment LDI temperatures in the Atlantic and Mozambique Channel compare well with the average LDI-derived temperatures from the overlying sediment traps, as well as with decadal annual mean SST. Lastly, we observed large seasonal variations in the diol index, as an indicator of upwelling conditions, at three sites: in the eastern Atlantic, potentially linked to Guinea Dome upwelling; in the Cariaco Basin, likely caused by seasonal upwelling; and in the Mozambique Channel, where diol index variations may be driven by upwelling from favorable winds and/or eddy migration.

  • Open Access English
    Authors: 
    Perner, Kerstin; Moros, Matthias; Jansen, Eystein; Kuijpers, Antoon; Troelstra, Simon; Prins, Maarten Arnoud;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: EC | ICE2ICE (610055)

    Expansion of fresh and sea-ice loaded surface waters from the Arctic Ocean into the sub-polar North Atlantic is suggested to modulate the northward heat transport within the North Atlantic Current (NAC). The Reykjanes Ridge south of Iceland is a suitable area to reconstruct changes in the mid- to late Holocene fresh and sea-ice loaded surface water expansion, which is marked by the Subarctic Front (SAF). Here, shifts in the location of the SAF result from the interaction of freshwater expansion and inflow of warmer and saline (NAC) waters to the Ridge. Using planktic foraminiferal assemblage and concentration data from a marine sediment core on the eastern Reykjanes Ridge elucidates SAF location changes and thus, changes in the water-mass composition (upper ~200 m) during the last c. 5.8 ka BP. Our foraminifer data highlight a late Holocene shift (at c. 3.0 ka BP) in water-mass composition at the Reykjanes Ridge, which reflects the occurrence of cooler and fresher surface waters when compared to the mid-Holocene. We document two phases of SAF presence at the study site: from (i) c. 5.5 to 5.0 ka BP and (ii) c. 2.7 to 1.5 ka BP. Both phases are characterized by marked increases in the planktic foraminiferal concentration, which coincides with freshwater expansions and warm subsurface water conditions within the sub-polar North Atlantic. We link the SAF changes, from c. 2.7 to 1.5 ka BP, to a strengthening of the East Greenland Current and awarming in the NAC, as identified by various studies underlying these two currents. From c. 1.5 ka BP onwards, we record a prominent subsurface cooling and continued occurrence of fresh and sea-ice loaded surface waters at the study site. This implies that the SAF migrated to the southeast of our core site during the last millennium.

  • Open Access English
    Authors: 
    Lamy, Frank; Chiang, John C H; Martínez Méndez, Gema; Thierens, Mieke; Arz, Helge Wolfgang; Bosmans, Joyce H C; Hebbeln, Dierk; Lambert, Fabrice; Lembke-Jene, Lester; Stuut, Jan-Berend W;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NSF | Collaborative Proposal: E... (1537496)

    The southern westerly wind belt (SWW) interacts with the Antarctic Circumpolar Current and strongly impacts the Southern Ocean carbon budget, and Antarctic ice-sheet dynamics across glacial- interglacial cycles. We investigated precipitation-driven sediment input changes to the Southeast Pacific off the southern margin of the Atacama Desert in Chile over the past one million years, revealing strong precession (19/23-ka) cycles. Our simulations with 2 ocean-atmosphere general circulation models suggest that observed cyclic rainfall changes are linked to meridional shifts in water vapor transport from the tropical Pacific toward the southern Atacama Desert. These changes reflect a precessional modulation of the split in the austral winter South Pacific jet stream. For precession maxima, we infer significantly enhanced rainfall in the southern Atacama Desert due to a stronger South Pacific split jet with enhanced subtropical/subpolar jets, and a weakermidlatitude jet. Conversely, we derive dry conditions in northern Chile related to reduced subtropical/subpolar jets and an enhanced midlatitude jet for precession minima. The presence of precessional cycles in the Pacific SWW, and lack thereof in other basins, indicate that orbital-scale changes of the SWW were not zonally homogeneous across the Southern Hemisphere, in contrast to the hemispherewide shifts of the SWW suggested for glacial terminations. The strengthening of the jet is unique to the South Pacific realm and might have affected winter-controlled changes in the mixed layer depth, the formation of intermediate water, and the built-up of sea-ice around Antarctica, with implications for the global overturning circulation and the oceanic storage of atmospheric CO2.

  • Other research product . Collection . Other ORP type . 2019
    Open Access English
    Authors: 
    Waelbroeck, Claire; Lougheed, Bryan C; Vázquez Riveiros, Natalia; Missiaen, Lise; Pedro, Joel B; Dokken, Trond; Hajdas, Irka; Wacker, Lukas; Abbott, Peter M; Dumoulin, Jean-Pascal; +53 more
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: EC | ACCLIMATE (339108), FCT | UID/Multi/04326/2019 (UID/Multi/04326/2019), EC | ICE2ICE (610055)

    Rapid changes in ocean circulation and climate have been observed in marine-sediment and ice cores over the last glacial period and deglaciation, highlighting the non-linear character of the climate system and underlining the possibility of rapid climate shifts in response to anthropogenic greenhouse gas forcing. To date, these rapid changes in climate and ocean circulation are still not fully explained. One obstacle hindering progress in our understanding of the interactions between past ocean circulation and climate changes is the difficulty of accurately dating marine cores. Here, we present a set of 92 marine sediment cores from the Atlantic Ocean for which we have established age-depth models that are consistent with the Greenland GICC05 ice core chronology, and computed the associated dating uncertainties, using a new deposition modeling technique. This is the first set of consistently dated marine sediment cores enabling paleoclimate scientists to evaluate leads/lags between circulation and climate changes over vast regions of the Atlantic Ocean. Moreover, this data set is of direct use in paleoclimate modeling studies.

  • Open Access English
    Authors: 
    Hollstein, Martina; Mohtadi, Mahyar; Rosenthal, Yair; Prange, Matthias; Oppo, Delia W; Martínez Méndez, Gema; Tachikawa, Kazuyo; Moffa-Sanchez, Paola; Steinke, Stephan; Hebbeln, Dierk;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science

    Surface and thermocline conditions of the Western Pacific Warm Pool (WPWP) reflect changes in regional and basin scale ocean and atmosphere circulations and in turn may affect climate globally. Previous studies suggest that a range of factors influences the WPWP on different timescales, however the precise forcings and mechanisms are unclear. Combining surface and thermocline records from sediment cores offshore Papua New Guinea we explore the influence of local and remote processes on the WPWP in response to astronomical forcing and changing glacial-interglacial boundary conditions over the past 110 kyr. We find that thermocline temperatures change with variations in Earth's obliquity with higher temperatures coinciding with high obliquity, which is attributed to variations in subduction and advection of the South Pacific Tropical Water. In contrast, rainfall variations associated with meridional migrations of the Intertropical Convergence Zone are primarily driven by changes in insolation due to precession. Records of bulk sedimentary Ti/Ca and foraminiferal Nd/Ca indicate an additional influence of obliquity, which, however, cannot unambiguously be related to changes in precipitation. Finally, our results suggest a thermocline deepening during the Last Glacial Maximum (LGM). A compilation of available proxy records illustrates a dipole-like pattern of LGM thermocline depth anomalies with a shoaling (deepening) in the northern (southern) WPWP. A comparison of the proxy compilation with an ensemble of Paleoclimate Model Intercomparison Project (PMIP) climate model simulations reveals that the spatial pattern of LGM thermocline depth anomalies is mainly attributable to a contraction of the Pacific Walker circulation on its western side.