Tracking atmospheric and riverine terrigenous supplies variability during the last glacial and the Holocene in central Mediterranean

Bout-Roumazeilles, Viviane; Combourieu-Nebout, Nathalie; Desprat, Stéphanie; Siani, Giuseppe; Turon, J-L

doi:10.5194/cpd-8-2921-2012

Cited by 6 publications

(7 citation statements)

References 176 publications

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“…4). Prevailing arid conditions in Tunisia during GS-1 are confirmed by large aeolian terrigenous supply as detected by high illite, palygorskite and zirconium contents in our core (Bout-Roumazeilles et al, 2012). Similar climatic variations were reported from Western Mediterranean marine pollen and SST records (Cacho et al, 2001;Fletcher and Sánchez Goñi, 2008;Combourieu-Nebout et al, 2009).…”

Section: Deglacial Vegetation and Climatic Changessupporting

confidence: 86%

Deglacial and Holocene vegetation and climatic changes at the southernmost tip of the Central Mediterranean from a direct land-sea correlation

Desprat¹,

Combourieu-Nebout²,

Essallami³

et al. 2012

Preprint

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Despite a large number of studies, the long-term and millennial to centennial-scale climatic variability in the Mediterranean region during the last deglaciation and the Holocene is still debated, in particular in the Southern Central Mediterranean. In this paper, we present a new marine pollen sequence (MD04-2797CQ) from the Siculo-Tunisian Strait documenting the regional vegetation and climatic changes in the Southern Central Mediterranean during the last deglaciation and the Holocene. <br><br> The MD04-2797CQ marine pollen sequence shows that semi-desert plants dominated the vegetal cover in the Southern Central Mediterranean between 18 and 12.3 kyr BP indicating prevailing dry conditions during the deglaciation, even during the Greenland Interstadial (GI)-1. Such arid conditions likely restricted the expansion of the trees and shrubs despite the GI-1 climatic amelioration. Across the transition Greenland Stadial (GS)-1 – Holocene, Asteraceae-Poaceae steppe became dominant till 10.1 kyr. This record underlines with no chronological ambiguity that even though temperatures increased, deficiency in moisture availability persisted into the Early Holocene.Temperate trees and shrubs with heaths as oak forest understorey or heath maquis expanded between 10.1 and 6.6 kyr, while Mediterranean plants only developed from 6.6 kyr onwards. These changes in vegetal cover show that the regional climate in Southern Central Mediterranean was wetter during Sapropel 1 (S1) and became drier during the Mid- to Late Holocene. Wetter conditions during S1 were likely due to increased winter precipitation while summers remained dry. We suggest, in agreement with published modelling experiments, that the increased melting of the Laurentide Ice Sheet between 10 to 6.8 kyr in conjunction with weak winter insolation played a major role in the development of winter precipitation maxima in the Mediterranean region in controlling the strength and position of the North Atlantic storm track. <br><br> Finally, our data provide evidences of centennial-scale vegetation and climatic changes in the Southern Central Mediterranean. During the wet Early Holocene, alkenones-derived cooling episodes are synchronous to herbaceous composition changes that indicate muted changes in precipitation. In contrast, enhanced aridity episodes, as detected by strong reduction in trees and shrubs, are recorded during the Mid- to Late Holocene. We show that the impact of the Holocene cooling events depend on the baseline climate states insolation and ice sheet volume, shaping the response of the mid-latitude atmospheric circulation

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Section: Deglacial Vegetation and Climatic Changessupporting

confidence: 86%

Deglacial and Holocene vegetation and climatic changes at the southernmost tip of the Central Mediterranean from a direct land-sea correlation

Desprat¹,

Combourieu-Nebout²,

Essallami³

et al. 2012

Preprint

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“…The Nile River flux during the LGM was assumed to be comparable with the Holocene, whereas it was multiplied by a factor of 2, 3, and 4 to examine its impact on ε Nd EMS values for the S1 case (Table ). We are aware that the dust contribution was higher than the present during the LGM (Bout‐Roumazeilles et al, ). However, since the net dust Nd contribution is small compared to Nd flux related to the seawater advection and partial Nile River particle dissolution in the EMS, the present‐day dust flux was applied to both of the sensitivity tests (Table ).…”

Section: Resultsmentioning

confidence: 94%

“…The age model of core MD04‐2797CQ is based on 13 radiocarbon dates using INTCAL09 (Reimer et al, ) and the 14 C calibration software CALIB 6 (Stuiver et al, ; Stuiver & Reimer, ) (Bout‐Roumazeilles et al, ; Desprat et al, ; Sicre et al, ) (Figure b). The interval studied encompasses the last 23 kyr (core top and 770 cm sediment samples respectively dated at 0.7 and 22.6 cal ka BP).…”

Section: Methodsmentioning

confidence: 99%

“…While for core MD04‐2722 a 400 year reservoir age was used for the entire interval studied (Cornuault et al, ; Tachikawa et al, ), different reservoir ages were considered for core MD04‐2797CQ: 400 years for the Holocene, the Younger Dryas, and the LGM, 560 years during the Bolling‐Allerod, and 800 years for the Heinrich event 1 and the Older Dryas (Bout‐Roumazeilles et al, ; Desprat et al, ; Sicre et al, ). Different reservoir ages and calibrations have only a limited impact on the final age model (less than 400 years, mean difference of about 90 years) as shown by the good consistency between the benthic foraminiferal δ 18 O records of the two cores (Figure b).…”

Section: Methodsmentioning

confidence: 99%

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Circulation Changes in the Eastern Mediterranean Sea Over the Past 23,000 Years Inferred From Authigenic Nd Isotopic Ratios

Cornuault

Tachikawa

Vidal

et al. 2018

Paleoceanog and Paleoclimatol

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The Eastern Mediterranean Sea (EMS) is a key region to study circulation change because of its own thermohaline circulation. In this study, we focused on intermediate/deep water circulation since the Last Glacial Maximum (LGM) including the sapropel S1 period. Two cores from the Levantine Sea and the Strait of Sicily, respectively, collected at 1,780 m and 771 m water depth, were studied using 143Nd/144Nd (εNd) of foraminiferal tests and leachates as well as benthic foraminiferal stable isotopes (δ13C, δ18O). This approach allowed the determination of variations in (1) the North Atlantic water contribution to the Mediterranean basin, (2) water exchanges at the Strait of Sicily, and (3) the influence of the Nile River over the last 23,000 years. During the LGM, high benthic foraminiferal δ13C values indicate well‐ventilated intermediate and deep waters in the EMS. The εNd values were more radiogenic than at present, reflecting a smaller contribution of unradiogenic North Atlantic waters to the EMS due to reduced exchange at the Strait of Sicily. The sluggish circulation in the EMS initiated during deglaciation was further enhanced by increased Nile River freshwater inputs between 15 ka BP and the S1 period. Partial dissolution of Nile River particles contributed to an increase in EMS εNd. The large εNd gradient between the EMS and the Western Mediterranean Sea observed during LGM and S1 suggests that each basin had a distinct circulation mode. Decreasing εNd values at the Strait of Sicily after S1 reflected improved water exchange between both basins, leading to the modern circulation pattern.

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“…The rhythmic formation of organic‐rich units, named sapropels (Olauson, ), is the profound evidence of the repeatedly disrupted Eastern Mediterranean thermohaline circulation in response to orbitally induced climate perturbations (Hilgen, ; Rossignol‐Strick, ). Specifically, these intervals reflect periods of more humid climate conditions for the circum‐Mediterranean (Bout‐Roumazeilles et al, ; Combourieu‐Nebout et al, 2013; Kallel et al, ; Magny et al, ; Siani et al, ) that further attest the basin's direct and indirect response to solar radiation related climate variability (Grant et al, ; Hennekam et al, ; Rossignol‐Strick, ; Ziegler et al, ). The latter is associated with the position of the Intertropical Convergence Zone (ITCZ) and monsoonal intensity, hence arid/humid conditions in North Africa, which in turn are closely linked to the Mediterranean water circulation, hence DW‐formation.…”

Section: Introductionmentioning

confidence: 99%

Eastern Mediterranean Deep Water Formation During Sapropel S1: A Reconstruction Using Geochemical Records Along a Bathymetric Transect in the Adriatic Outflow Region

Filippidi

Lange

2019

Paleoceanog and Paleoclimatol

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Eastern Mediterranean thermohaline circulation is directly influenced by middle‐ and low‐latitude climate systems. The dramatic paleoclimate changes during the last African Humid Period (~10–6 ka BP) were captured in Mediterranean sediments as the distinctly organic‐rich unit sapropel S1. Here, deepwater formation variability during S1 deposition is reconstructed. We use geochemical records of three cores along a bathymetric transect (775‐, 1,359‐, and 1,908‐m water depths), at the transition between the Adriatic DW‐ formation area and the Eastern Mediterranean. In all three cores, sedimentation rates are distinctly higher during S1, corresponding with enhanced runoff emanating from the Adriatic hinterland. Hence, major runoff did not only come from southern but also from northern borderlands in this period. During sapropel formation, enhanced levels of primary productivity occurred in the surface waters and oxygen‐depleted conditions in the bottom waters for all sites. Conditions for sediment and bottom‐water below ~1.4 km water depth were sulfidic throughout S1, but for intermediate depth (775 m) were anoxic only during the first part (S1a). Bottom‐water oxygenation interrupted S1 formation at water depths down to ~1.4 km, during two brief episodes, at 8.2 and 7.4 cal. ka BP. From the 7.4 cal. ka BP ventilation onward, the transition to more oxygenated bottom‐water conditions was more progressive for the intermediate water depth site (775 m) than for the deeper sites. Conditions remained fully oxic for all water depths following the S1‐MarkerBed ventilation event. Possibly, the onset of continuously oxic conditions started slightly earlier at intermediate depth (775 m; 6.6 ± 0.3 cal. ka BP) than at greater depths (1,359 m, 1,908 m; 6.0 ± 0.3 cal. ka BP).

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Tracking atmospheric and riverine terrigenous supplies variability during the last glacial and the Holocene in central Mediterranean

Cited by 6 publications

References 176 publications

Deglacial and Holocene vegetation and climatic changes at the southernmost tip of the Central Mediterranean from a direct land-sea correlation

Deglacial and Holocene vegetation and climatic changes at the southernmost tip of the Central Mediterranean from a direct land-sea correlation

Circulation Changes in the Eastern Mediterranean Sea Over the Past 23,000 Years Inferred From Authigenic Nd Isotopic Ratios

Eastern Mediterranean Deep Water Formation During Sapropel S1: A Reconstruction Using Geochemical Records Along a Bathymetric Transect in the Adriatic Outflow Region

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