Orbital- and Millennial-Scale Variability in Northwest African Dust
Emissions Over the Past 67,000 years
Abstract
Reconstructions of aeolian dust flux to West African margin sediments
can be used to explore changing atmospheric circulation and hydroclimate
over North Africa on millennial to orbital timescales. Here, we extend
West African margin dust flux records back to 35 ka in a transect of
core sites from 19°N to 27°N, and back to 67 ka at Ocean Drilling
Program (ODP) Hole 658C, in order to explore the interplay of orbital
and high-latitude forcings on North African climate and make
quantitative estimates of dust flux during the core of the Last Glacial
Maximum (LGM). The ODP 658C record shows a “Green Sahara” interval
from 60 to 50 ka during a time of high Northern Hemisphere summer
insolation, with dust fluxes similar to levels during the early Holocene
African Humid Period, and an abrupt peak in flux during Heinrich event
5a (H5a). Dust fluxes increase from 60 to 35 ka while the high-latitude
Northern Hemisphere cools, with peaks in dust flux associated with North
Atlantic cool events. From 35 ka through the LGM dust deposition
decreases in all cores, and little response is observed to low-latitude
insolation changes. Dust fluxes at sites north of 20°N were near late
Holocene levels during the LGM time slice, suggesting a more muted LGM
response than observed in mid-latitude dust sources. Records along the
northwest African margin suggest important differences in wind responses
during different stadials, with maximum dust flux anomalies centered
south of 20°N during H1 and north of 20°N during the Younger Dryas.