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Monsoon-driven Saharan dust variability over the past 240,000 years

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Presentation on theme: "Monsoon-driven Saharan dust variability over the past 240,000 years"— Presentation transcript:

1 Monsoon-driven Saharan dust variability over the past 240,000 years
by C. Skonieczny, D. McGee, G. Winckler, A. Bory, L. I. Bradtmiller, C. W. Kinsley, P. J. Polissar, R. De Pol-Holz, L. Rossignol, and B. Malaizé Science Volume 5(1):eaav1887 January 2, 2019 Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).

2 Fig. 1 Modern dust over North Africa and core sites discussed in the text.
Modern dust over North Africa and core sites discussed in the text. Map of mean annual (2000–2017) dust aerosol optical depth (AOD) over the North African continent, the northeastern Atlantic Ocean, the Mediterranean Sea, and the Gulf of Aden (off East Africa). Dust AOD data are from the 555-nm nonspherical AOD retrieval averaged between 2000 and 2017 from the Multiangle Imaging Spectroradiometer (source: Giovanni, NASA EarthData). Cores discussed in the manuscript are plotted: sites MD (this study) and ODP659 (3) in the northeast Atlantic, site ODP967 in the eastern Mediterranean Sea (28), and core RC in the Gulf of Aden (17). MD and ODP659 are located under the present-day dust plumes transporting Saharan dust across the Atlantic Ocean. C. Skonieczny et al. Sci Adv 2019;5:eaav1887 Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).

3 Fig. 2 Dust and paleoceanographic records from core MD03-2705 off West Africa.
Dust and paleoceanographic records from core MD off West Africa. (A) 230Th-normalized dust fluxes (red). (B) Northern Hemisphere summer insolation (June-July-August, 65°N; dashed lines) (29). (C) Dust percentages (gray). (D and E) δ18Oben (green) and δ13Cben (orange) values from benthic foraminifera (25). (F and G) 230Th-normalized CaCO3 flux (blue) and total sediment flux (black). All uncertainties are 1-σ. Gray bars highlight periods when high dust percentages occur in association with low 230Th-normalized sedimentation rates and carbonate accumulation rates, indicating that these dust percentage maxima are driven by carbonate dissolution rather than eolian supply. C. Skonieczny et al. Sci Adv 2019;5:eaav1887 Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).

4 Fig. 3 Power spectral analysis of Saharan dust and carbonate records.
Power spectral analysis of Saharan dust and carbonate records. Power spectral analyses (top) and associated coherences (bottom) conducted with the AnalySeries software (46). (A) ODP659 and MD dust percentages, (B) MD Th-normalized dust fluxes, and (C) MD Th-normalized carbonate fluxes for the past 240 ka. Dashed line represents ODP659 data, and black line represents MD data. Gray bars highlight the main orbital cyclicities (100, 41, and 23 ka) for which a peak in power variance is associated with a coherence higher than 0.5. While the length of the studied period (240 ka) is too short to make firm conclusions about 100-ka cyclicity, the changes in 41- and 23-ka variabilities are robust. C. Skonieczny et al. Sci Adv 2019;5:eaav1887 Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).

5 Fig. 4 African monsoon belt records and orbital forcing.
African monsoon belt records and orbital forcing. (A) Northern Hemisphere summer insolation (65°N; dashed lines). (B) 230Th-normalized Saharan dust fluxes from core MD (red; reversed scale). (C) Sapropel numbers from ODP967 in the eastern Mediterranean Sea, reflecting peaks in Nile River runoff (28). (D) δD values in leaf waxes from core RC in the Gulf of Aden (blue) (17). (E) Eccentricity-tilt-precession (ETP) parameter (gray) (29). Gray bars highlight maxima of 65°N summer insolation, demonstrating consistent monsoon responses to most insolation maxima and skipped beats during glacial maxima. C. Skonieczny et al. Sci Adv 2019;5:eaav1887 Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).

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