0000000001328740
AUTHOR
Nicola Pelosi
Holocene millennial-scale productivity variations in the Sicily Channel (Mediterranean Sea)
[1] The calcareous nannofossil assemblages of Ocean Drilling Program Hole 963D from the central Mediterranean Sea have been investigated to document oceanographic changes in surface waters. The studied site is located in an area sensitive to large-scale atmospheric and climatic systems and to high- and low-latitude climate connection. It is characterized by a high sedimentation rate (the achieved mean sampling resolution is <70 years) that allowed the Sicily Channel environmental changes to be examined in great detail over the last 12 ka BP. We focused on the species Florisphaera profunda that lives in the lower photic zone. Its distribution pattern shows repeated abundance fluctuations of …
The response of calcareous nannoplankton to sea surface variability at Ceara Rise during the early Pleistocene glacial-interglacial cycles
The Ceara Rise lies just beyond the edge of the Amazon River Fan and sediments from this site may record the complex interplay of different climatic systems and processes, including past changes in southern America monsoon activity, Intertropical Convergence Zone setting, different Atlantic Meridional Overturning Circulation (AMOC) strength and phytoplankton blooming triggered by Amazon River plumes. Here we investigate early Pleistocene calcareous nannoplankton at Ceara Rise, between about 1150 and 850 kiloyears ago. Our investigation shows abrupt variations in water column dynamics across glacial/interglacial cycles or, even better, linked with different AMOC modes. Dominant placoliths in…
Millenial-scale paleoenviromental changes in the central Mediterranean during the Last Interglacial: comparison with European and North Atlantic records.
Abstract The environment of the central Mediterranean Sea is investigated on the basis of high-resolution planktonic foraminifera and calcareous nannofossil data (mean sampling resolutions of about 80 and 160 yr, respectively). MIS 5 is characterized by warm, oligotrophic and stratified waters, while coccolithophore communities developed a vertical zonation that, in today's oceans, is typical of the low-latitude gyres. The temperate-subtropical configuration of planktonic foraminifera and calcareous nannofossil assemblages is repeatedly transformed into a temperate-subpolar one during the suborbital cooling episodes C25-C18. A comparison with European pollen sequences and North Atlantic cor…
Astronomic forcing on the planktonic foraminifera assemblage in the Piacenzian Punta Piccola section (southern Italy)
[1] A high-resolution quantitative analysis of the calcareous planktonic assemblages (planktonic foraminifers and calcareous nannofossils) at the Punta Piccola section (at the base of which, the global standard stratotype-section and point of the Piacenzian stage is defined) provided a more accurate biostratigraphy for the Mediterranean middle Pliocene (2.6–3.6 Ma). In particular, an astronomically calibrated age of 2.87 Ma was estimated for the Pliocene first occurrence of Neogloboquadrina atlantica instead of the younger previously proposed age of 2.72 Ma. Spectral analysis performed on the Globigerinoides species (spp.) planktonic foraminifera assemblage along with cross-spectral analysi…
A 4500 year record of palaeomagnetic secular variation and relative palaeointensity from the Tyrrhenian Sea
A marine sediment core from the western Mediterranean provides a newhigh-resolution 4,500-year record of palaeomagnetic secular variation and relativepalaeointensity. In 2013, the 7.1-metre C5 core was recovered from the TyrrhenianSea as part of the NextData climate data project. The coring site, 15 km offshorefrom the Volturno river mouth, is well-located to record combined marine andterrestrial palaeoclimatic influences, and the fine-grained, rapidly deposited sedimentsare effective palaeomagnetic recorders. We investigate the palaeomagnetic field direction and strength recorded in the core, which provide a valuable high-resolution recordof Holocene geomagnetic variation in the area. Usin…
Middle-late Pleistocene eastern Mediterranean nutricline depth and coccolith preservation linked to Monsoon activity and Atlantic meridional overturning circulation
Altres ajuts: Unidad de excelencia María de Maeztu CEX2019-000940-M; Universidade de Vigo's programme to attract excellent research talent (RR04092017) The eastern Mediterranean Sea lies under the influence of high- and low-latitude climatic systems. The northern part of the basin is affected by Atlantic depressions and continental and polar air masses that promote intermediate and deep-water formation. The southern part is influenced by subtropical conditions and monsoon activity. Monsoon intensification results in enhanced freshwater discharge from the Nile River and other (now dry) systems along the North African margin. This freshwater influx into the Mediterranean Sea reduces surface w…
Holocene climate variability of the Western Mediterranean: Surface water dynamics inferred from calcareous plankton assemblages
A high-resolution study (centennial scale) has been performed on the calcareous plankton assemblage of the Holocene portion of the Ocean Drilling Program Site 976 (Alboran Sea) with the aim to identify the main changes in the surface water dynamic. The dataset also provided a seasonal foraminiferal sea surface water temperatures (SSTs), estimated using the modern analog technique SIMMAX 28, and it was compared with available geochemical and pollen data at the site. Three main climate shifts were identified as (1) the increase in abundance of Syracosphaera spp. and Turborotalita quinqueloba marks the early Holocene humid phase, during maximum summer insolation and enhanced river runoff. It i…
Evidence for a link between the Atlantic Multidecadal Oscillation and annual asthma mortality rates in the US
AbstractAn association between climatic conditions and asthma mortality has been widely assumed. However, it is unclear whether climatic variations have a fingerprint on asthma dynamics over long time intervals. The aim of this study is to detect a possible correlation between climatic indices, namely the Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation, and asthma mortality rates over the period from 1950 to 2015 in the contiguous US. To this aim, an analysis of non-stationary and non-linear signals was performed on time series of US annual asthma mortality rates, AMO and PDO indices to search for characteristic periodicities. Results revealed that asthma death rates evalu…
Centennial- to millennial-scale climate oscillations in the Central-Eastern Mediterranean Sea between 20,000 and 70,000 years ago: Evidence from a high-resolution geochemical and micropaleontological record
Abstract Here we present a high-resolution faunal, floral and geochemical (stable isotopes and trace elements) record from the sediments of Ocean Drilling Program Site 963 (central Mediterranean basin), which shows centennial/millennial-scale resemblance to the high-northern latitude rapid temperature fluctuations documented in the Greenland ice cores between 20 and 70 kyr BP. Oxygen and carbon isotopes, planktic foraminifera and calcareous nannofossil distributions suggest that Dansgaard–Oeschger (D/O) and Heinrich events (HE) are distinctly expressed in the Mediterranean climate record. Moreover, recurrent though subdued oscillations not previously identified in the Lateglacial Mediterran…
Orbital variations in planktonic foraminifera assemblages from the Ionian Sea during the Middle Pleistocene Transition
Abstract The Middle Pleistocene Transition (1.2–0.7 Ma) is the most recent re-organization of the global climate system which includes variations in the frequency and amplitude of glacial/interglacial cycles, increased ice sheet volume, sea surface temperature cooling and a significant drop in the CO 2 atmospheric levels. Here we present high-resolution planktonic foraminifera data (mean sampling resolution of about 780 years) from core LC10 recovered in the Ionian Sea (eastern Mediterranean), between 1.2 and 0.9 Ma. Selected taxa, among them G. ruber , T. quinqueloba and G. bulloides , show significant periodicities that can be associated to orbital cycles, mainly precession and obliquity.…
Primary productivity variability on the Atlantic Iberian Margin over the last 70,000 years: Evidence from coccolithophores and fossil organic compounds
[1] This study analyzes coccolithophore abundance fluctuations (e.g., Emiliania huxleyi, Gephyrocapsa specimens, and Florisphaera profunda) in core MD01-2444 sediment strata retrieved at the Iberian Margin, northeastern Atlantic Ocean. Coccolithophores are calcareous nannofossils, a major component of the oceanic phytoplankton, which provide information about past ecological and climatological variability. Results are supported by data on fossil organic compounds (sea surface temperatures, alkenones, and n-hexacosan-1-ol index) and geochemical analyses (benthic δ13Ccc and planktonic δ18Occ isotopes). Three scenarios are taken into account for this location at centennial-scale resolution ove…
Productivity modes in the Mediterranean Sea during Dansgaard–Oeschger (20,000–70,000 yr ago) oscillations
The study of planktonic organisms during abrupt climatic variations of the last glacial period (Dansgaard-Oeschger oscillations, D-O) may reveal important insights on climatic, oceanographic and biological interactions. Here we present planktic foraminifera and coccolithophore data collected at the Ocean Drilling Program Site 963 (Sicily Channel), with a mean sampling resolution of respectively 43.5 and 98.9. yr, over the interval between 70,000 and 20,000. yr ago. The paleoenvironmental reconstruction suggests that three different scenarios can be seen across each D-O cycle: 1. oligotrophic surface water and a deep thermocline for the early Interstadials; 2. a Deep Chlorophyll Maximum and …
Mediterranean coccolith ecobiostratigraphy since the penultimate Glacial (the last 145,000years) and ecobioevent traceability
The Mediterranean Sea is a miniature ocean ideal to test the response of marine ecosystems to amplified orbital and suborbital climate changes. Here we present coccolith data from a Sardinia Channel gravity core (Arcose C_33) analysed over the last 145,000 years, with a mean resolution of about 900 years. The study highlights that regional phytoplankton assemblages underwent significant modifications between the penultimate glacial and the last interglacial, as well as between the last glacial and the Holocene. The N ratio palaeoproductivity index suggests reduced productivity levels and the development of a deep nutricline during the last interglacial and the Holocene. Within the last glac…
Chemistry of Globigerinoides ruber shells from ODP Site 160-963
Here we present a high-resolution faunal, floral and geochemical (stable isotopes and trace elements) record from the sediments of Ocean Drilling Program Site 963 (central Mediterranean basin), which shows centennial/millennial-scale resemblance to the high-northern latitude rapid temperature fluctuations documented in the Greenland ice cores between 20 and 70 kyr BP. Oxygen and carbon isotopes, planktic foraminifera and calcareous nannofossil distributions suggest that Dansgaard-Oeschger (D/O) and Heinrich events (HE) are distinctly expressed in the Mediterranean climate record. Moreover, recurrent though subdued oscillations not previously identified in the Lateglacial Mediterranean sedim…