L’étude du pollen des séquences sédimentaires marines pour la compréhension du climat : l’exemple des périodes chaudes passées

Desprat, Stéphanie; Oliveira, Dulce; Naughton, Filipa; Goñi, Marı́a Fernanda Sánchez

doi:10.4000/quaternaire.8102

Cited by 12 publications

(14 citation statements)

References 75 publications

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“…The samples were subsequently diluted to Ca concentrations similar to the standard solutions. Calibration was conducted following the method described by de Villiers et al (2002) using standards with constant Ca concentrations and different Sr concentrations to provide Sr/Ca ratios ranging from 0.75 to 4 mmol/mol. All measurements were conducted using the ICP-AES (Thermo ICAP DUO 6300) in the Geology Department at the University of Oviedo with a reproducibility better than 0.02 mmol/mol.…”

Section: Sample Preparation and Sr/ca Analysismentioning

confidence: 99%

Coccolithophore productivity at the western Iberian Margin during the Middle Pleistocene (310–455 ka) – evidence from coccolith Sr∕Ca data

et al. 2020

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Abstract. Coccolithophores contribute significantly to marine primary productivity and play a unique role in ocean biogeochemistry by using carbon for photosynthesis (soft-tissue pump) and for calcification (carbonate counter pump). Despite the importance of including coccolithophores in Earth system models to allow better predictions of the climate system's responses to planetary change, the reconstruction of coccolithophore productivity mostly relied on proxies dependent on accumulation and sedimentation rates and preservation conditions. In this study we used an independent proxy, based on the coccolith fraction (CF) Sr∕Ca ratio, to reconstruct coccolithophore productivity. We studied the marine sediment core MD03-2699 from the western Iberian margin (IbM), concentrating on glacial–interglacial cycles of Marine Isotopic Stage (MIS) 12 to MIS 9. We found that IbM coccolithophore productivity was controlled by changes in the oceanographic conditions, such as in sea surface temperature (SST) and nutrient availability, and by competition with other phytoplankton groups. Long-term coccolithophore productivity was primarily affected by variations in the dominant surface water mass. Polar and subpolar surface waters during glacial substages were associated with decreased coccolithophore productivity, with the strongest productivity minima concomitant with Heinrich-type events (HtEs). Subtropical, nutrient-poorer waters, increased terrigenous input, and moderate to strong upwelling during the deglaciation and early MIS11 are hypothesized to have attributed a competitive advantage to diatoms to the detriment of coccolithophores, resulting in intermediate coccolithophore productivity levels. During the progression towards full glacial conditions an increasing presence of nutrient-richer waters, related to the growing influence of transitional surface waters and/or intensified upwelling, probably stimulated coccolithophore productivity to maxima following the rapid depletion of silica by diatoms. We present conceptual models of the carbon and carbonate cycle components for the IbM in different time slices that might serve as a basis for further investigation and modelling experiments.

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Section: Sample Preparation and Sr/ca Analysismentioning

confidence: 99%

Coccolithophore productivity at the western Iberian Margin during the Middle Pleistocene (310–455 ka) – evidence from coccolith Sr∕Ca data

et al. 2020

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“…These Iberian margin sequences are each composed of three cores: the southern sequence is a composite of cores MD95-2042, MD01-2443, and IODP U1385 located at around 37°N ( Figure 5 ; Sánchez Goñi et al, 1999 , 2016b ; Roucoux et al, 2006 ; Chabaud et al, 2014 ; Oliveira et al, 2016 ), and the northern one is a composite of cores MD99-2331, MD01-2447, and MD03-2697 collected at 42°N ( Desprat et al, 2005 , 2006 , 2007 , 2009 ; Sánchez Goñi et al, 2005 , 2008 ; Naughton et al, 2007 , 2009 , 2016 ). The pollen analysis of the 425,000-year northern sequence is completed ( Desprat et al, 2017 ) while that of the southern site is in progress ( Figure 5 ). Further north, the sequence MD04-2845 collected on the European margin, off western France, spans the last 140,000 years ( Sánchez Goñi et al, 2008 , 2012 ).…”

Section: European Vegetation and Climate Response To Long-term And Ramentioning

confidence: 99%

“…Pollen data are compared to CO 2 and CH 4 records from ice cores ( Siegenthaler et al, 2005 ; Spahni et al, 2005 ; Loulergue et al, 2008 ; Luthi et al, 2008 ) and astronomical forcing ( Berger, 1978 ). Adapted from Desprat et al (2017) .…”

Section: European Vegetation and Climate Response To Long-term And Ramentioning

confidence: 99%

“…Pollen records from the Iberian margin show that the magnitude of forest development substantially differed from one interglacial to another in the south (MIS 19 to MIS 1, Mediterranean forest pollen = 40 to 80%, Figure 5 ), while in the north the magnitude of the forest expansion was similar (Atlantic forest pollen = 80%; Desprat et al, 2017 ). These data suggest that temperatures were similarly warm during the last five interglacials in northwestern Iberia, whereas the amount of winter precipitation in the south was quite variable.…”

Section: European Vegetation and Climate Response To Long-term And Ramentioning

confidence: 99%

“…(Right) Schematic representation of the vegetation in the Iberian Peninsula, atmospheric and surface ocean circulations and temperature gradient in the North Atlantic during millennial events of MIS 19c and MIS 11c. Adapted from Desprat et al (2017) .…”

Section: Interactions Between Millennial and Orbital Climate Variabilmentioning

confidence: 99%

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Pollen from the Deep-Sea: A Breakthrough in the Mystery of the Ice Ages

et al. 2018

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Pollen from deep-sea sedimentary sequences provides an integrated regional reconstruction of vegetation and climate (temperature, precipitation, and seasonality) on the adjacent continent. More importantly, the direct correlation of pollen, marine and ice indicators allows comparison of the atmospheric climatic changes that have affected the continent with the response of the Earth's other reservoirs, i.e., the oceans and cryosphere, without any chronological uncertainty. The study of long continuous pollen records from the European margin has revealed a changing and complex interplay between European climate, North Atlantic sea surface temperatures (SSTs), ice growth and decay, and high-and low-latitude forcing at orbital and millennial timescales. These records have shown that the amplitude of the last five terrestrial interglacials was similar above 40 • N, while below 40 • N their magnitude differed due to precessionmodulated changes in seasonality and, particularly, winter precipitation. These records also showed that vegetation response was in dynamic equilibrium with rapid climate changes such as the Dangaard-Oeschger (D-O) cycles and Heinrich events, similar in magnitude and velocity to the ongoing global warming. However, the magnitude of the millennial-scale warming events of the last glacial period was regionally-specific. Precession seems to have imprinted regions below 40 • N while obliquity, which controls average annual temperature, probably mediated the impact of D-O warming events above 40 • N. A decoupling between high-and low-latitude climate was also observed within last glacial warm (Greenland interstadials) and cold phases (Greenland stadials). The synchronous response of western European vegetation/climate and eastern North Atlantic SSTs to D-O cycles was not a pervasive feature throughout the Quaternary. During periods of ice growth such as MIS 5a/4, MIS 11c/b and MIS 19c/b, repeated millennial-scale cold-air/warm-sea decoupling events occurred on the European margin superimposed to a long-term air-sea decoupling trend. Strong air-sea thermal contrasts promoted the production of water vapor that was then transported northward by the Frontiers in Plant Science | www.frontiersin.org 1 January 2018 | Volume 9 | Article 38Sánchez Goñi et al.Pollen and Ice Ages westerlies and fed ice sheets. This interaction between long-term and shorter timescale climatic variability may have amplified insolation decreases and thus explain the Ice Ages. This hypothesis should be tested by the integration of stochastic processes in Earth models of intermediate complexity.

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The MIS 13 interglacial at Ceprano, Italy, in the context of Middle Pleistocene vegetation changes in southern Europe

Margari

Roucoux

Magri

et al. 2018

Quaternary Science Reviews

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Climatic and environmental changes of the Middle Pleistocene in Europe provide the context for an important phase in the evolution and dispersal of early hominins. Pollen records from terrestrial and marine sediment sequences reveal patterns not usually visible in palaeoenvironmental reconstructions from archaeological sites alone and show that hominin evolution took place against a background of marked environmental change as forests expanded and contracted in concert with global and regional climatic shifts. It is rare to find archaeological material in stratigraphically long and continuous palaeoenvironmental sequences, yet this is what is needed to enable particular phases of hominin evolution to be securely associated with climatic and environmental changes. At the well-known Middle Pleistocene archaeological site of Ceprano in Italy we have been able to produce a pollen record from the sedimentary unit directly below the stratum of the hominin remains. The new pollen data from Ceprano are presented here in full for the first time and provide a detailed picture of interglacial vegetation development during Marine Isotope Stage (MIS) 13. This evidence contributes significantly to our knowledge of the spatial heterogeneity of ecosystem responses to climatic change during this period and helps to further constrain the age of the hominin remains. New sites combining both archaeology and long, continuous high quality palaeoecological records would help clarify the relationship between hominin presence and palaeoclimatic and palaeoenvironmental conditions. In the meantime, better communication between the research communities can also go a long way to improving our understanding of the links between the two.

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L’étude du pollen des séquences sédimentaires marines pour la compréhension du climat : l’exemple des périodes chaudes passées

Cited by 12 publications

References 75 publications

Coccolithophore productivity at the western Iberian Margin during the Middle Pleistocene (310–455 ka) – evidence from coccolith Sr∕Ca data

Coccolithophore productivity at the western Iberian Margin during the Middle Pleistocene (310–455 ka) – evidence from coccolith Sr∕Ca data

Pollen from the Deep-Sea: A Breakthrough in the Mystery of the Ice Ages

The MIS 13 interglacial at Ceprano, Italy, in the context of Middle Pleistocene vegetation changes in southern Europe

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