Research ArticleCLIMATOLOGY

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

See allHide authors and affiliations

Science Advances  02 Jan 2019:
Vol. 5, no. 1, eaav1887
DOI: 10.1126/sciadv.aav1887
  • Fig. 1 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 MD03-2705 (this study) and ODP659 (3) in the northeast Atlantic, site ODP967 in the eastern Mediterranean Sea (28), and core RC09-166 in the Gulf of Aden (17). MD03-2705 and ODP659 are located under the present-day dust plumes transporting Saharan dust across the Atlantic Ocean.

  • Fig. 2 Dust and paleoceanographic records from core MD03-2705 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.

  • Fig. 3 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 MD03-2705 dust percentages, (B) MD03-2705 230Th-normalized dust fluxes, and (C) MD03-2705 230Th-normalized carbonate fluxes for the past 240 ka. Dashed line represents ODP659 data, and black line represents MD03-2705 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.

  • Fig. 4 African monsoon belt records and orbital forcing.

    (A) Northern Hemisphere summer insolation (65°N; dashed lines). (B) 230Th-normalized Saharan dust fluxes from core MD03-2705 (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 RC09-166 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.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/1/eaav1887/DC1

    Supplementary Material and Methods

    Supplementary Text

    Fig. S1. MD03-2705 age model for the past 240 ka.

    Fig. S2. Sedimentological parameters used in the dust MAR calculation for MD03-2705 and ODP659 for the past 240 ka.

    Fig. S3. Power spectral analysis of MD03-2705 and ODP659 dust MARs.

    Fig. S4. Power spectral analysis of MD03-2705 230Th-normalized dust flux records at the extremes of 1-σ uncertainties.

    Fig. S5. Comparison between MD03-2705 230Th-normalized CaCO3 fluxes and reconstructed [CO32−] from Cibicidoides wuellerstorfi B/Ca between 90 and 50 ka.

    Fig. S6. Power spectral analysis of RC09-166 δDwax (East Africa).

    Table S1. Age control points used to build the chronology of the past 240 ka of core MD03-2705.

    Table S2. MD03-2705 core depth, model age, thorium and uranium activities, and carbonate content as well as sediment, dust, and carbonate fluxes for the past 240 ka.

    References (5073)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Material and Methods
    • Supplementary Text
    • Fig. S1. MD03-2705 age model for the past 240 ka.
    • Fig. S2. Sedimentological parameters used in the dust MAR calculation for MD03-2705 and ODP659 for the past 240 ka.
    • Fig. S3. Power spectral analysis of MD03-2705 and ODP659 dust MARs.
    • Fig. S4. Power spectral analysis of MD03-2705 230Th-normalized dust flux records at the extremes of 1-σ uncertainties.
    • Fig. S5. Comparison between MD03-2705 230Th-normalized CaCO3 fluxes and reconstructed CO32− from Cibicidoides wuellerstorfi B/Ca between 90 and 50 ka.
    • Fig. S6. Power spectral analysis of RC09-166 δDwax (East Africa).
    • Table S1. Age control points used to build the chronology of the past 240 ka of core MD03-2705.
    • Table S2. MD03-2705 core depth, model age, thorium and uranium activities, and carbonate content as well as sediment, dust, and carbonate fluxes for the past 240 ka.
    • References (5073)

    Download PDF

    Files in this Data Supplement:

Navigate This Article