Features and lessons from Past Interglacials ? warm periods ? over the last 1.5 Ma

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Early Pleistocene calcareous nannofossil assemblages from the Gulf of Cadiz reveal glacial-interglacial and millennial-scale variability

Publication . Trotta, Samanta; Marino, Maria; H L Voelker, Antje; Rodrigues, Teresa; Maiorano, Patrizia; Flores, José-Abel; Girone, Angela; Addante, Marina; Balestra, Barbara

Coccolithophore high resolution (300 years) quantitative analyses have been carried out on Early Pleistocene sediment samples from Integrated Ocean Drilling Program Site U1387 retrieved in the Gulf of Cadiz. The studied interval is well constrained by the delta 18O chronological frame and covers marine isotope stage (MIS) 48 to MIS 45, from 1465.9 ka to 1389.9 ka. The aim is to investigate paleoenvironmental changes during a poorly known interval of the "41 ky world" and understand how climate dynamics controlled coccolithophore abundance and variation at orbital up to millennial scale. Assemblage composition variation and Principal Component Analysis (PCA) indicate that temperature and nutrient availability are the main factors influencing coccolithophores. Precession forcing combined with hydrological and atmospheric dynamics affect changes in coccolithophore assemblage composition and abundance highlighting glacial-interglacial cycles and a millennial scale variability, which is more evident during glacials than during interglacials. Interglacial MIS 47 onset is more abrupt than MIS 45 inception in relation to a more prominent insolation maximum, which favors the sharp increase and highest abundance of warm water taxa in the early MIS 47. Short-term abundance peaks of C. pelagicus spp. pelagicus during glacials document polar-subpolar melting water influx into the Gulf of Cadiz and southward migration of the subpolar front during episodes of high volume ice-sheet in the north hemisphere and reduced Atlantic Meridional Overturning circulation. In late MIS 48 the lowest coccolithophore productivity, induced by colder and stratified surface waters, a terminal stadial has been inferred. Enhanced short-term glacial productivity is favored by higher mixing and nutrient content in surface water due to the strengthened westerly winds during symbolscript phases. This promotes arid condition and upwelling along the studied site. The interglacial short-term coccolithophore productivity increases are associated with insolation maxima and enhanced nutrients of land origin during more humid periods led by -NAO-like phases, which induce the southward position of the westerlies and higher precipitation in the Mediterranean region and North Africa, in agreement with the contemporary sapropel occurrences in Mediterranean Sea. Our data-set suggests a connection between climate dynamics in the Gulf of Cadiz and east of Gibraltar Strait during the Early Pleistocene as well as a relationship with the north hemisphere ice-sheet dynamics.

2022-12Journal article

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A southern Portuguese Margin Perspective of Marine Isotope Stage 47—An interglacial in the 41 kyr World

Publication . Voelker, Antje; Rodrigues, Teresa; Trotta, Samanta; Marino, Maria; Kuhnert, Henning

In order to better understand interglacial climate variability within the 41 kyr world, we produced high-resolution climate records for interglacial Marine Isotope Stage (MIS) 47 (1424-1452 ka) at IODP Site U1387 (36 degrees 48 ' N, 7 degrees 43 ' W) on the southern Portuguese margin. Using benthic and planktonic foraminifera stable isotope records, U-37(k') sea-surface temperature (SST), and plankton assemblage data we investigated Mediterranean Outflow Water (MOW) and surface water conditions. The MOW-level records indicate a poorly ventilated and sluggish bottom current during the MIS 48/MIS 47 transition in association with the insolation maximum, whereas a well-ventilated MOW formed a contourite layer during the second insolation maximum. The benthic delta O-18 record shows a fairly abrupt change during the deglaciation of MIS 48, while the surface waters experienced a terminal stadial event that was associated with initial cooling and freshening followed by stepwise warming until interglacial SST was reached at 1450 ka. Interglacial conditions with SST of 24 degrees C or higher persisted until 1427 ka, although warm SST prevailed into MIS 46. The persistent and prolonged warmth is attributed to a northward expansion of the subtropical gyre during MIS 47 as reflected by the dominance of subtropical-tropical planktonic foraminifera species and the presence of warm water coccolithophores taxa.

2022Journal article

Open access

Marine Isotope Stage 4 (71–57 ka) on the Western European margin: insights to the drainage and dynamics of the Western European Ice Sheet

Publication . Toucanne, Samuel; Rodrigues, Teresa; Menot, Guillemette; Soulet, Guillaume; Cheron, Sandrine; Billy, Isabelle; Eynaud, Frederique; Antoine, Pierre; Sinninghe Damste, Jaap S.; Bard, Edouard; Sanchez Goñi, Maria-Fernanda

Marine Isotope Stage (MIS) 4 (ca. 71–57 ka; within the Middle Weichselian Substage) is considered a significant Pleistocene glaciation, but it remains poorly constrained in comparison to that of the Late Weichselian Last Glacial Maximum (LGM; ca. 29–19 ka, during MIS 2), or even the Late Saalian MIS 6 (ca. 190–130 ka). Most MIS 4 glacial landforms in Europe were erased by the more extensive LGM ice advance, precluding a robust recon struction of its extent and dynamic through time. Marine sedimentary archives, in preserving the source-to-sink sediment transfer signals of ice-sheet and glacier processes, help to bridge this gap. Here, the signals west of the European Ice Sheet (EIS) are tracked for MIS 4 from the deep Bay of Biscay (NE Atlantic), which was the outlet for Fennoscandian Ice Sheet (FIS) sediment-laden meltwater during extensive glaciations, specifically when the British-Irish Ice Sheet (BIIS) and the FIS coalesced into the North Sea (as during MIS 6 and the LGM). Sedi mentological, geochemical, and mineralogical proxies reveal the absence of FIS-derived material in Bay of Biscay sediment throughout MIS 4, which indicates that FIS meltwater and huge river systems from the North European Plain never drained into the Bay of Biscay at that time. This suggests that contrary to MIS 6 and the LGM, the BIIS and FIS were not likely large enough to coalesce and form a (grounded) ice bridge onto the North Sea, thus confirming geomorphic evidence for a significant, but relatively limited, glaciation in Europe during MIS 4. Closer to the Bay of Biscay, ice-marginal fluctuations of the BIIS are identified in the Celtic-Irish Sea region from the deep-sea record. More specifically, our findings suggest an early retreat of the Irish Sea Ice Stream as soon as ca. 68–65 ka, a few millennia before the demise of the EIS, and the Northern Hemisphere ice sheets as a whole, during Heinrich Stadial (HS) 6. This pattern is similar to that already recorded during MIS 2. Finally, this study reveals that the MIS 4 period in Western Europe corresponds, as for MIS 2, to a complex combination of general ice advance interspersed by preliminary-to-final EIS demises highlighted by HS conditions.

2023Journal article

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Paleoproductivity proxies and alkenone precursors in the Western Mediterranean during the Early-Middle Pleistocene transition

Publication . Marino, Maria; Rodrigues, Teresa; Quivelli, Ornella; Girone, Angela; Maiorano, Patrizia; Bassinot, Franck

Multidisciplinary analyses (taxonomic analysis of coccolithophore assemblages, stable oxygen isotopes, marine and terrestrial biomarkers) have been carried out on sediments from Ocean Drilling Program Site 975 in the Algero-Balearic basin, through late marine isotope stage (MIS) 20-19 (800-756 ka). The aim is to compare coccolithophore paleoproductivity proxies, such as C-37 alkenone concentration and nannofossil accumulation rate (NAR), and understand their relationship with paleoceanographic condition and paleoenvironmental changes, alkenone-producing precursors and unsaturated C-37 alkenone compounds. The patterns of C-37 alkenones and NAR provide reliable information on past paleoproductivity changes since coccolith dissolution and organic matter preservation were excluded as relevant processes at the site. This is testified by the high values of Nannofossil Dissolution Index and relation between C-37 alkenone concentration and Alcohol Preservation Index, the latter used as a proxy of sea bottom ventilation in the basin. A weak mismatching between NAR and C-37 alkenone concentration records has been observed and related to paleoenvironmental factors and ecological preferences of alkenone-producing species. Temperature variations mostly controlled the alternating interspecific abundance variations of these taxa through glacial-interglacial and stadial-interstadial climate phases. The percentage abundances of alkenone-producing species, Gephyrocapsa caribbeanica and Gephyrocapsa with open central area (mainly G. margerelii-G. muellerae) strongly co-varied with the percentages of C-37:2 and C-37:3, respectively during warm and cool-cold periods, suggesting their prominent role in producing these unsaturated C-37 alkenone compounds. Moreover, Gephyrocapsa spp. with open central area > 3 mu m were likely the main C-37:4 producers during the colder late MIS 20 stadial and stadial phases. Other factors in addition to temperature influenced the paleoproductivity proxy patterns. The oceanographic condition established during MIS 20-MIS 19 deglaciation and the more nutrient-rich surface waters during the orbitally-controlled organic-rich layer deposition in the early MIS 19 enhanced primary productivity leading to higher production and preservation of total C-37 alkenones.

2022-09Journal article

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Persistent influence of obliquity on ice age terminations since the Middle Pleistocene transition

Publication . Bajo, Petra; Drysdale, Russell N.; Woodhead, Jon D.; Hellstrom, John C.; Hodell, David; Ferretti, Patrizia; Voelker, Antje; Zanchetta, Giovanni; Rodrigues, Teresa; Wolff, Eric; Tyler, Jonathan; Frisia, Silvia; Spötl, Christoph; Fallick, Anthony E.

Radiometric dating of glacial terminations over the past 640,000 years suggests pacing by Earth’s climatic precession, with each glacial-interglacial period spanning four or five cycles of ~20,000 years. However, the lack of firm age estimates for older Pleistocene terminations confounds attempts to test the persistence of precession forcing. We combine an Italian speleothem record anchored by a uranium-lead chronology with North Atlantic ocean data to show that the first two deglaciations of the so-called 100,000-year world are separated by two obliquity cycles, with each termination starting at the same high phase of obliquity, but at opposing phases of precession. An assessment of 11 radiometrically dated terminations spanning the past million years suggests that obliquity exerted a persistent influence on not only their initiation but also their duration.

2020Journal article

Open access