Changes in biological productivity along the northwest African margin over the past 20,000 years
Bradtmiller, Louisa I.
Kinsley, Christopher W.
deMenocal, Peter B.
MetadataShow full item record
The intertropical convergence zone and the African monsoon system are highly sensitive to climate forcing at orbital and millennial timescales. Both systems influence the strength and direction of the trade winds along northwest Africa and thus directly impact coastal upwelling. Sediment cores from the northwest African margin record upwelling-related changes in biological productivity connected to changes in regional and hemispheric climate. We present records of 230Th-normalized biogenic opal and Corg fluxes using a meridional transect of four cores from 19°N–31°N along the northwest African margin to examine changes in paleoproductivity since the last glacial maximum. We find large changes in biogenic fluxes synchronous with changes in eolian fluxes calculated using end-member modeling, suggesting that paleoproductivity and dust fluxes were strongly coupled, likely linked by changes in wind strength. Opal and Corg fluxes increase at all sites during Heinrich Stadial 1 and the Younger Dryas, consistent with an overall intensification of the trade winds, and changes in the meridional flux gradient indicate a southward wind shift at these times. Biogenic fluxes were lowest, and the meridional flux gradients were weakest during the African Humid Period when the monsoon was invigorated due to precessional changes, with greater rainfall and weaker trade winds over northwest Africa. These results expand the spatial coverage of previous paleoproxy studies showing similar changes, and they provide support for modeling studies showing changes in wind strength and direction consistent with increased upwelling during abrupt coolings and decreased upwelling during the African Humid Period.
Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 31 (2016): 185–202, doi:10.1002/2015PA002862.
Showing items related by title, author, creator and subject.
Data report of oblique reflection-refraction radio-sonobuoy profiles on the African Atlantic continental margin : (R/V Atlantis II cruises 67 and 75) Hoskins, Hartley; Rogers, Carolyn U.; Woo, Aileen O. (Woods Hole Oceanographic Institution, 1974-06)Two hundred sixty-four unreversed oblique reflection-refraction profiles using expendable radio-sonobuoys were obtained during two geophysical cruises to the Atlantic continental margin of Africa. This data report gives ...
Semidiurnal temperature changes caused by tidal front movements in the warm season in seabed habitats on the Georges Bank northern margin and their ecological implications Guida, Vincent G.; Valentine, Page C.; Gallea, Leslie B. (Public Library of Science, 2013-02-06)Georges Bank is a large, shallow feature separating the Gulf of Maine from the Atlantic Ocean. Previous studies demonstrated a strong tidal-mixing front during the warm season on the northern bank margin between thermally ...
Characterization of sills associated with the U reflection on the Newfoundland margin : evidence for widespread early post-rift magmatism on a magma-poor rifted margin Peron-Pinvidic, Gwenn; Shillington, Donna J.; Tucholke, Brian E. (John Wiley & Sons, 2010-05-25)Drilling during ODP Leg 210 penetrated two post-rift sills (dated as ∼105.3 and ∼97.8 Ma) in the deep sediments overlying basement of the continent–ocean transition zone on the magma-poor Newfoundland margin. The sill ...