title: Glacial to Holocene changes in trans-Atlantic Saharan dust transport and dust-climate feedbacks.
abstract: Saharan mineral dust exported over the tropical North Atlantic is thought to have significant impacts on regional climate and ecosystems, but limited data exist documenting past changes in long-range dust transport. This data gap limits investigations of the role of Saharan dust in past climate change, in particular during the mid-Holocene, when climate models consistently underestimate the intensification of the West African monsoon documented by paleorecords. We present reconstructions of African dust deposition in sediments from the Bahamas and the tropical North Atlantic spanning the last 23,000 years. Both sites show early and mid-Holocene dust fluxes 40 to 50% lower than recent values and maximum dust fluxes during the deglaciation, demonstrating agreement with records from the northwest African margin. These quantitative estimates of trans-Atlantic dust transport offer important constraints on past changes in dust-related radiative and biogeochemical impacts. Using idealized climate model experiments to investigate the response to reductions in Saharan dust's radiative forcing over the tropical North Atlantic, we find that small (0.15°C) dust-related increases in regional sea surface temperatures are sufficient to cause significant northward shifts in the Atlantic Intertropical Convergence Zone, increased precipitation in the western Sahel and Sahara, and reductions in easterly and northeasterly winds over dust source regions. Our results suggest that the amplifying feedback of dust on sea surface temperatures and regional climate may be significant and that accurate simulation of dust's radiative effects is likely essential to improving model representations of past and future precipitation variations in North Africa.
authors.affiliation: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Ross H
authors.identifier: 0000-0002-3819-4926
authors.initials: RH
authors.lastname: Williams
authors.affiliation: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: David
authors.identifier: 0000-0002-7329-3428
authors.initials: D
authors.lastname: McGee
authors.affiliation: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.; Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
authors.forename: Christopher W
authors.identifier: 0000-0002-3185-520X
authors.initials: CW
authors.lastname: Kinsley
authors.affiliation: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: David A
authors.identifier: 0000-0003-3890-0197
authors.initials: DA
authors.lastname: Ridley
authors.affiliation: Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA.
authors.forename: Shineng
authors.initials: S
authors.lastname: Hu
authors.affiliation: Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA.
authors.forename: Alexey
authors.initials: A
authors.lastname: Fedorov
authors.affiliation: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Irit
authors.initials: I
authors.lastname: Tal
authors.affiliation: Department of Earth and Environment, Boston University, Boston, MA 02215, USA.
authors.forename: Richard W
authors.identifier: 0000-0002-7688-4098
authors.initials: RW
authors.lastname: Murray
authors.affiliation: Department of Earth and Environmental Sciences, Columbia University, New York, NY 10027, USA.; Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA.
authors.forename: Peter B
authors.initials: PB
authors.lastname: deMenocal
keywords: African Humid Period; Mineral dust; North Africa; paleoclimate