Research ArticlePALEOCLIMATE

Glacial to Holocene changes in trans-Atlantic Saharan dust transport and dust-climate feedbacks

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Science Advances  23 Nov 2016:
Vol. 2, no. 11, e1600445
DOI: 10.1126/sciadv.1600445
  • Fig. 1 Modern dust transport over the North Atlantic basin.

    (A) Map of boreal summer [June-July-August-September (JJAS)] dust aerosol optical depth (AOD) (color bar) over the North Atlantic showing the transport of African dust across the basin. Contours show r2 values for the relationship between dust deposition at the Bahamas core sites (100GGC and 103GGC, indicated by the star) and dust loading over the rest of the North Atlantic in the Goddard Earth Observing System–Chemistry (GEOS-Chem) model (3). Correlations are significant for r2 > 0.2. Inset shows correlation between modeled mean dust AOD over the Bahamas and dust AOD averaged over the mid-Atlantic (0°N to 30°N and 0°W to 50°W) in JJAS for each year from 1982 to 2008. (B) As in (A), but for boreal winter [December-January-February-March (DJFM)] and with spatial correlations calculated for the central TNA core site (VM20-234, indicated by the star). The circle shows the site of the African margin flux record shown in Fig. 2 (OCE437-7 GC68). Dust AOD data are from the 558-nm nonspherical AOD retrieval averaged over May to September between 2004 and 2008 from the Multiangle Imaging Spectroradiometer (MISR) (76).

  • Fig. 2 African dust fluxes over the last 23 ky from locations spanning the low-latitude North Atlantic.

    (A) Summertime [June-July-August (JJA)] insolation at 20°N (77). (B) Dust flux reconstruction at northwest African margin site OCE437-7 GC68 (15). (C) Dust flux reconstructions from Bahamas sediment cores 100GGC (white triangles) and 103GGC (blue circles). (D) Dust flux reconstruction from TNA core VM20-234. The portion of the Bahamas record before 13 ka and the entirety of the VM20-234 record are not expected to record the amplitude or timing of millennial-scale changes in dust deposition due to low sedimentation rates. 1σ uncertainties are shown for each record’s dust fluxes. Time intervals indicated at the top of the plot are as follows: AHP, African Humid Period; YD, Younger Dryas stadial; BA, Bølling-Allerød interstadial; HS1, Heinrich Stadial 1; LGM, Last Glacial Maximum.

  • Fig. 3 Coupled climate model simulation of the impacts of reduced dust loading over the TNA.

    (A to D) JAS changes in the reduced dust simulation (“All_n50p”) relative to the preindustrial control for (A) surface temperature (°C), (B) precipitation (mm/day), (C) low-level specific humidity (g/kg) and winds (vectors; m/s), and (D) low-level water vapor convergence (mm/day) and water vapor transport (vectors; kg·m/s). Low level is defined as an average from the surface to approximately 830 hPa. Stippling in (A) and (B) indicates significance at P < 0.1.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/11/e1600445/DC1

    Supplementary Materials and Methods

    fig. S1. Map showing core sites for Bahamas cores OCE205-2 100GGC and 103GGC.

    fig. S2. Age-depth plots for OCE205-2 100GGC and 103GGC.

    fig. S3. Comparison of focusing factors and reconstructed dust fluxes in core 103GGC.

    fig. S4. Test of the impact of bioturbation on the deglacial portion of the Bahamas record.

    fig. S5. Map showing core site for core VM20-234 along the Mid-Atlantic Ridge.

    fig. S6. Age-depth plot and sedimentation rates for VM20-234.

    fig. S7. Ternary diagram comparing the trace element compositions of Bahamas sediments and soils and potential sources of terrigenous sediment.

    fig. S8. Sea-level pressure changes in the GCM experiment.

    fig. S9. Slab ocean simulation of the impacts of reduced dust loading over the subtropical North Atlantic.

    fig. S10. Climate mean state from the preindustrial control run of the coupled climate model.

    fig. S11. Relationship between surface temperatures and rainfall in the preindustrial slab ocean control simulation.

    data file S1. U-Th data and dust fluxes.

    data file S2. Radiocarbon data from core VM20-234.

    data file S3. Trace element data from Bahamas sediments.

    References (7894)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Materials and Methods
    • fig. S1. Map showing core sites for Bahamas cores OCE205-2 100GGC and 103GGC.
    • fig. S2. Age-depth plots for OCE205-2 100GGC and 103GGC.
    • fig. S3. Comparison of focusing factors and reconstructed dust fluxes in core 103GGC.
    • fig. S4. Test of the impact of bioturbation on the deglacial portion of the Bahamas record.
    • fig. S5. Map showing core site for core VM20-234 along the Mid-Atlantic Ridge.
    • fig. S6. Age-depth plot and sedimentation rates for VM20-234.
    • fig. S7. Ternary diagram comparing the trace element compositions of Bahamas sediments and soils and potential sources of terrigenous sediment.
    • fig. S8. Sea-level pressure changes in the GCM experiment.
    • fig. S9. Slab ocean simulation of the impacts of reduced dust loading over the subtropical North Atlantic.
    • fig. S10. Climate mean state from the preindustrial control run of the coupled climate model.
    • fig. S11. Relationship between surface temperatures and rainfall in the preindustrial slab ocean control simulation.
    • Legends for data file S

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    Other Supplementary Material for this manuscript includes the following:

    • data file S1 (Microsoft Excel format). U-Th data and dust fluxes.
    • data file S2 (Microsoft Excel format). Radiocarbon data from core VM20-234.
    • data file S3 (Microsoft Excel format). Trace element data from Bahamas sediments.

    Download data files S1 to S3

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