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  • 1
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    Black Sea hydroclimate and coupled hydrology was strongly controlled by high-latitude glacial climate dynamics (2021)
    Nature Publishing Group UK
    Details
    Publication Date: 2023-09-14
    Description: Abstract The Black Sea experienced pronounced millennial-scale changes in temperature and rainfall during the last glacial coinciding with Dansgaard-Oeschger cycles. However, little is known regarding the amount and sources of freshwater reaching this inland basin. Here, we present detailed ostracod δ〈sup〉18〈/sup〉O data from the glacial Black Sea showing subdued Dansgaard-Oeschger cyclicity and four prominent longer-term saw-tooth shaped Bond-like cycles. We propose that the δ〈sup〉18〈/sup〉Oostracods signature primarily reflects changes in the atmospheric circulation in response to the waxing and waning Eurasian Ice Sheet. The millennial-scale ice sheet variations likely resulted not only in latitudinal migrations of atmospheric frontal systems but also in shifts of dominant moisture sources for the Black Sea. Heavier isotopic precipitation arrived from the North Atlantic-Mediterranean realm during the warmer interstadials and lighter isotopic precipitation from the Eurasian continental interior during the colder stadials. The subdued Dansgaard-Oeschger variability likely reflects an integrated precipitation signal additionally affected by the long mixing times of the large Black Sea volume up to 1,500 years as suggested from hydrologic-isotope-balance modelling.
    Description: Moisture sources to the Black Sea changed in response to atmospheric frontal displacements driven by Eurasian Ice Sheet dynamics during the last glacial period, according to analyses of ostracod oxygen and strontium isotope data from Black Sea sediments.
    Description: Deutsche Forschungsgemeinschaft (German Research Foundation) https://doi.org/10.13039/501100001659
    Description: https://doi.org/10.5281/zenodo.4545579
    Keywords: ddc:551 ; paleohydrology ; palaeoclimate ; Black Sea ; Archangelsky Ridge ; isotope geochemistry ; Dansgaard-Oeschger cycles
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 2
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    2. Wochenbericht POS507 (2016)
    IOW
    In:  IOW, Warnemünde, Germany, 2 pp.
    Details
    Publication Date: 2016-11-16
    Description: FS Poseidon Reise 507 - Sedimenttransport im Landsort Tief und die holozäne Paläozeanographie der zentralen Ostsee, Warnemünde - Warnemünde (15.10.-02.11.2016)
    Type: Report , NonPeerReviewed
    Format: text
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    OceanRep: Report - Weekly report
  • 3
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    1. Wochenbericht POS507 (2016)
    In:  UNSPECIFIED, 2 pp.
    Details
    Publication Date: 2016-11-16
    Description: FS Poseidon Reise 507 - Sedimenttransport im Landsort Tief und die holozäne Paläozeanographie der zentralen Ostsee, Warnemünde - Warnemünde (15.10.-02.11.2016)
    Type: Report , NonPeerReviewed
    Format: text
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    OceanRep: Report - Weekly report
  • 4
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    North Atlantic control on precipitation pattern in the eastern Mediterranean/Black Sea region during the last glacial (2009)
    Elsevier
    In:  Quaternary Research, 71 . pp. 375-384.
    Details
    Publication Date: 2019-09-23
    Description: Based on proxy records from western Black Sea cores, we provide a comprehensive study of climate change during the last glacial maximum and late-glacial period in the Black Sea region. For the first time we present a record of relative changes in precipitation for NW Anatolia based on variations in the terrigenous supply expressed as detrital carbonate concentration. The good correspondence between reconstructed rainfall intensity in NW Anatolia and past western Mediterranean sea surface temperatures (SSTs) implies that during the glacial period the precipitation variability was controlled, like today, by Mediterranean cyclonic disturbances. Periods of reduced precipitation correlate well with low SSTs in the Mediterranean related to Heinrich events H1 and H2. Stable oxygen isotopes and lithological and mineralogical data point to a significant modification in the dominant freshwater/sediment source concomitant to the meltwater inflow after 16.4 cal ka BP. This change implies intensification of the northern sediment source and, with other records from the Mediterranean region, consistently suggests a reorganization of the atmospheric circulation pattern affecting the hydrology of the European continent. The early deglacial northward retreat of both atmospheric and oceanic polar fronts was responsible for the warming in the Mediterranean region, leading simultaneously to more humid conditions in central and northern Europe.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.yqres.2008.12.004
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Abrupt changes of temperature and water chemistry in the late Pleistocene and early Holocene Black Sea (2008)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 9 (Q01004).
    Details
    Publication Date: 2018-03-08
    Description: New Mg/Ca, Sr/Ca, and published stable oxygen isotope and 87Sr/86Sr data obtained on ostracods from gravity cores located on the northwestern Black Sea slope were used to infer changes in the Black Sea hydrology and water chemistry for the period between 30 to 8 ka B.P. (calibrated radiocarbon years). The period prior to 16.5 ka B.P. was characterized by stable conditions in all records until a distinct drop in δ18O values combined with a sharp increase in 87Sr/86Sr occurred between 16.5 and 14.8 ka B.P. This event is attributed to an increased runoff from the northern drainage area of the Black Sea between Heinrich Event 1 and the onset of the Bølling warm period. While the Mg/Ca and Sr/Ca records remained rather unaffected by this inflow; they show an abrupt rise with the onset of the Bølling/Allerød warm period. This rise was caused by calcite precipitation in the surface water, which led to a sudden increase of the Sr/Ca and Mg/Ca ratios of the Black Sea water. The stable oxygen isotopes also start to increase around 15 ka B.P., although in a more gradual manner, due to isotopically enriched meteoric precipitation. While Sr/Ca remains constant during the following interval of the Younger Dryas cold period, a decrease in the Mg/Ca ratio implies that the intermediate water masses of the Black Sea temporarily cooled by 1–2°C during the Younger Dryas. The 87Sr/86Sr values drop after the cessation of the water inflow at 15 ka B.P. to a lower level until the Younger Dryas, where they reach values similar to those observed during the Last Glacial Maximum. This might point to a potential outflow to the Mediterranean Sea via the Sea of Marmara during this period. The inflow of Mediterranean water started around 9.3 ka B.P., which is clearly detectable in the abruptly increasing Mg/Ca, Sr/Ca, and 87Sr/86Sr values. The accompanying increase in the δ18O record is less pronounced and would fit to an inflow lasting ∼100 a.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2007GC001683
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Major hydrological shifts in the Black Sea “Lake” in response to ice sheet collapses during MIS 6 (130–184 ka BP) (2019)
    Elsevier
    In:  Quaternary Science Reviews, 219 . pp. 126-144.
    Details
    Publication Date: 2022-01-31
    Description: The Saalian was one of the largest glaciations during the Quaternary with an ice sheet extending considerably wider into the Eurasian continent than during other glacials. Orbital variations caused the ice sheet to switch between growing and shrinking. The partial retreat of the ice sheet and meltwater discharge resulted in global sea-level rise and increased lake levels of inland seas with broader environmental implications. During Marine Isotope Stage 6 (MIS 6), meltwater entered the formerly enclosed Black Sea at least twice as documented in a δ¹⁸O record from Anatolian speleothems. Here we present a sedimentary record from the Black Sea “Lake” covering MIS 6 and provide evidence for three meltwater periods coinciding with insolation maxima (BSWP-6-1: 180-167 ka BP, BSWP-6-2: 160-145 ka BP, BSWP-II: 133-130 ka BP). While δ¹⁸Oostracods and Sr/Caostracods point to pronounced meltwater supply and decreasing salinity, ⁸⁷Sr/⁸⁶Srostracods shed light on meltwater sources and pathways. During all three periods, meltwater drained most likely via the Dnieper and Volga into the Black and Caspian Seas and connected both basins. Relatively low ⁸⁷Sr/⁸⁶Srostracods values during the oldest meltwater period suggest melting solely of the eastern Eurasian Ice Sheet. In contrast, during the younger meltwater periods, exceptional high ⁸⁷Sr/⁸⁶Srostracods values point towards additional meltwater from the western Eurasian Ice Sheet. A surplus from melting glaciers in the Tian Shan and Pamir Mountains that finally entered the Caspian Sea via the Amu Darya and Sry Darya probably amplified the input of high radiogenic Sr-isotope water. We also show that higher temperatures and productivity suggest Dansgaard-Oeschger-like climate variability during the first half of MIS 6.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.quascirev.2019.07.008
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Determination and quantification of sedimentary processes in salt marshes using end‐member modelling of grain‐size data (2023)
    Wiley
    Details
    Publication Date: 2024-02-07
    Description: End-member modelling of bulk grain-size distributions allows the unravelling of natural and anthropogenic depositional processes in salt marshes and quantification of their respective contribution to marsh accretion. The sedimentology of two marshes is presented: (1) a sheltered back-barrier marsh; and (2) an exposed, reinstated foreland marsh. Sedimentological data are supplemented by an age model based on lead-210 decay and caesium-137, as well as geochemical data. End-member modelling of grain-size data shows that marsh growth in back-barrier settings is primarily controlled by the settling of fines from suspension during marsh inundation. In addition, nearby active dunes deliver aeolian sediment (up to 77% of the total sediment accretion), potentially enhancing the capability of salt marshes to adapt to sea-level rise. Growth of exposed marshes, by contrast, primarily results from high-energy inundation and is attributed to two sediment-transport processes. On the seaward edge of the marsh, sedimentation is dominated by coarser-grained traction load, whereas further inland, settling of fine-grained suspension load prevails. In addition, a third, coarse-grained sediment sub-population is interpreted to derive from anthropogenic land-reclamation measures, that is material from drainage channels relocated onto the marsh surface. This process contributed up to 34% to the total marsh accretion and terminated synchronously with the end of land reclamation measures. Data suggest that natural sediment supply to marshes alone is sufficient to outpace contemporary sea-level rise in the study area. This underlines the resilience potential of salt marshes in times of rising sea levels. The comparison of grain-size sub-populations with observed climate variability implies that even managed marshes allow for the extraction of environmental signals if natural and anthropogenic sedimentary processes are determined and their relative contribution to bulk sediment composition is quantified. Data series based solely on bulk sediments, however, seem to be of limited use because it is difficult to exclude bias of natural signals by anthropogenic measures.
    Type: Article , PeerReviewed
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Orbital- and millennial-scale Antarctic Circumpolar Current variability in Drake Passage over the past 140,000 years (2021)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: The Antarctic Circumpolar Current (ACC) plays a crucial role in global ocean circulation by fostering deep-water upwelling and formation of new water masses. On geological time-scales, ACC variations are poorly constrained beyond the last glacial. Here, we reconstruct changes in ACC strength in the central Drake Passage in vicinity of the modern Polar Front over a complete glacial-interglacial cycle (i.e., the past 140,000 years), based on sediment grain-size and geochemical characteristics. We found significant glacial-interglacial changes of ACC flow speed, with weakened current strength during glacials and a stronger circulation in interglacials. Superimposed on these orbital-scale changes are high-amplitude millennial-scale fluctuations, with ACC strength maxima correlating with diatom-based Antarctic winter sea-ice minima, particularly during full glacial conditions. We infer that the ACC is closely linked to Southern Hemisphere millennial-scale climate oscillations, amplified through Antarctic sea ice extent changes. These strong ACC variations modulated Pacific-Atlantic water exchange via the “cold water route” and potentially affected the Atlantic Meridional Overturning Circulation and marine carbon storage.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Surface sediment characteristics related to provenance and ocean circulation in the Drake Passage sector of the Southern Ocean (2019)
    In:  EPIC3Deep Sea Research Part I: Oceanographic Research Papers, 154, pp. 103135, ISSN: 09670637
    Details
    Publication Date: 2020-02-18
    Description: Understanding present-day sediment provenance and transport processes is crucial for studies about the dynamics of ocean circulation, as well as for paleoclimate reconstructions in the Drake Passage (DP), a key area for Earth's global oceanic circulation and climate during past and future. Based on a comprehensive set of surface sediment samples, we used spatial variations in grain-size distribution, bulk sediment mineralogy, silt and clay mineralogy across the entire DP region to elucidate the terrigenous sources and transport mechanisms. The statistical evaluation of these data identifies southern Patagonia (carbonate, illite, chlorite, feldspar and quartz) and the Antarctic Peninsula (chlorite, smectite, and amphibole) as the main sources for terrigenous sediments in the DP region. Different current systems are transporting the sediment material. Here, we provide a new, robust flow speed calibration for silt grain-sizes to enable the reconstruction of Antarctic Circumpolar Current (ACC) dynamics in the DP sector of the Southern Ocean. We correlated the sortable silt mean grain-size records of surface sediments with adjacent long-term current meter data. A clear bottom current speed pattern shows the variability of the ACC in the DP responding to the dynamics of ocean fronts, in agreement with modern observation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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    PAPER (OA)
  • 10
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    Sedimentary perspectives of Pleistocene ocean circulation and climate change from the southernmost Chilean continental margin (2019)
    American Geophysical Union
    In:  EPIC3AGU Centennial Fall Meeting, San Francisco, CA, USA, 2019-12-09-2019-12-13American Geophysical Union
    Details
    Publication Date: 2020-05-14
    Description: IODP Exp. 383 recovered two Pleistocene sedimentary sequences from the upper continental slope along the southernmost Chilean margin that are well positioned to monitor changes in the Antarctic Circumpolar Current (ACC) upstream of the Drake Passage and the history of Patagonian glaciation. These sites are characterized by high sedimentation rates and a complex distribution of siliciclastic sediments with infrequent decimeter-scale beds of calcareous biogenic sediments. Unravelling ocean circulation and climate history from these sites requires a primary understanding of sedimentary provenance and transport mechanisms derived from a complete lithological characterization of the sequence. Here, we integrate downcore shipboard physical properties with sedimentological observations to fully characterize the sequences, evaluate potential for correlation and constrain regional depositional processes. Site U1542 (52°S; 1101 m water depth) consists of a 249 m spliced sedimentary sequence containing Middle Pleistocene to Holocene sediments. It mainly consists of clayey silt that is often interbedded with thin (~75 cm) beds of calcareous sand-bearing clayey to sandy silt with foraminifera and nannofossils or foraminifera-rich nannofossil ooze. Site U1544 (55°S; 2090 m water depth) consists of a 98 m sedimentary sequence obtained from a single hole. Sediments are also dominated by silty clay, but exhibit slightly thicker beds of calcareous ooze and a significantly higher proportion of cm- to dm-scale sand beds that are interpreted as turbidites. Based on the lithology of the recovered sediments and proximity to a glaciated continental margin, terrigenous sediment is likely delivered to these locations by a combination of ice rafting, glacial meltwater plumes, episodic downslope transport from the outer continental shelf and fine-grained sediments transported by the Cape Horn Current entering the Drake Passage as the northern branch of the ACC.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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    PAPER (OA)
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