Browsing by Author "Ferretti, Patrizia"
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- Monsoon variability and high latitude climate signals in the Central Mediterranean at the Pliocene- Pleistocene transition: The Gelasian stratotype section (Monte San Nicola, Sicily) [Global and Planetary Change, volume 249, 104788]: CommentPublication . Zanola, Elena; Bonomo, Sergio; Incarbona, Alessandro; Tesei, Telemaco; Stefano, Agata Di; Ferretti, Patrizia; Fornaciari, Eliana; Galeotti, Simone; Macrì, Patrizia; Raffi, Isabella; Rodrigues, Teresa; Speranza, Fabio; Stefano, Enrico Di; Sprovieri, Rodolfo; Rio, Domenico; Capraro, LucaThe stratigraphic record of Monte San Nicola (southern Sicily, Italy), where the Global Boundary Stratotype Section and Point (GSSP) for the Gelasian Stage (Lower Pleistocene) has been defined, has been studied by our research group for fifteen years. In 2021, another working group (GELSTRAT) started investigating the Monte San Nicola stratigraphy in a location close to the GSSP section, with results that differ significantly from those published by our team. In particular, major discrepancies in the alkenone-derived paleotemperature reconstructions led the GELSTRAT team to suggest that our age model is invalid, and they inferred that we had made a wrong interpretation of the physical stratigraphic record. In this comment, we demonstrate that our chronological model is correct, while the stratigraphic profile studied by the GELSTRAT team should be approached with care, due to the presence of tectonic displacements, truncations, and uncertain lithological evidence for critical marker beds, such as the sapropel layers below the Nicola bed.
- Orbital and suborbital temperature variability in the central Mediterranean across the Pliocene/Pleistocene transitionPublication . Zanola, Elena; Rodrigues, Teresa; Bonomo, Sergio; Ferretti, Patrizia; Fornaciari, Eliana; Stefano, Agata Di; Incarbona, Alessandro; Preto, Nereo; Raffi, Isabella; Capraro, Luca; Jessica L. OsterA high-resolution record of central Mediterranean Sea Surface Temperatures (SSTs) based on the alkenone U-37(K') index and planktic delta O-18 values for the surface-dweller G. ruber has been reconstructed across the Pliocene/Pleistocene transition at Monte San Nicola (Sicily), reference area for the GSSP (Global Boundary Stratotype Section and Point) of the Gelasian Stage. Spectral analyses indicate that the SST record is predominantly paced by a cyclicity in the similar to 47 kyr time domain, consistent with the obliquity driven glacial-interglacial variability that is expected to dominate in the interval of relevance. In addition, two suborbital periodicities in the similar to 5 kyr and similar to 8 kyr time domains provide a pervasive spectral signal that proves to be especially strong during the MIS (Marine Isotope Stage) 100 glacial, at the inception of the Northern Hemisphere Glaciation. This high frequency climatic instability, a prominent feature of the early Gelasian, might reflect episodic events of massive disruption of the Atlantic Meridional Overturning Circulation with increased production of cold, low-salinity water masses in the North Atlantic. Alternatively, it may be interpreted as the resonance (i.e., harmonics) of the low-latitude precessional forcing in mid-latitude regions. Although the driving mechanisms of these processes remain largely unconstrained, our study emphasizes the role of the central Mediterranean as the main reference for high-resolution paleoclimatic studies in the Neogene and the Quaternary.
- Persistent influence of obliquity on ice age terminations since the Middle Pleistocene transitionPublication . 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.
- Pronounced northward shift of the westerlies during MIS 17 leading to the strong 100-kyr ice age cyclesPublication . Goni, Maria Fernanda Sanchez; Ferretti, Patrizia; Polanco-Martinez, Josue M.; Rodrigues, Teresa; Alonso-Garcia, Montserrat; Javier Rodriguez-Tovar, Francisco; Dorador, Javier; Desprat, StephanieThe MIS 17 interglacial, similar to 715-675 ka, marks the end of the Mid-Pleistocene Transition as intensified, long and asymmetrical 100-kyr ice age cycles became eminently established. Increasing arrival of moisture to the Northern Hemisphere high latitudes, resulting from the northwestward migration of the Subpolar Front and the intensification of the Norwegian Greenland Seas (NGS) convection, has been put forward to explain the emergence of this quasi-periodic 100-kyr cycle. However, testing this hypothesis is problematic with the available North Atlantic precipitation data. Here we present new pollen-based quantitative seasonal climate reconstructions from the southwestern Iberian margin that track changes in the position and intensity of the westerlies. Our data compared to changes in North Atlantic deep and surface water conditions show that MIS 17 interglacial was marked by three major changes in the direction and strength of the westerlies tightly linked to oceanographic changes. In particular, we report here for the first time a drastic two-steps northward shift of the westerlies centered at similar to 693 ka that ended up with the sustained precipitation over southern European. This atmospheric reorganization was associated with northwestward migration of the Subpolar Front, strengthening of the NGS deep water formation and cooling of the western North Atlantic region. This finding points to the substantial arrival of moisture to the Northern Hemisphere high latitudes at the time of the decrease in summer energy and insolation contributing to the establishment of strong 100-kyr cycles. (C) 2019 Elsevier B.V. All rights reserved.