Orbital‐ and Millennial‐Scale Variability in Northwest African Dust Emissions Over the Past 67,000 years
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 37 ka in a transect of sites from 19° to...
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| Published in: | Paleoceanography and paleoclimatology Vol. 37; no. 1 |
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| Main Authors: | , , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Hoboken
Blackwell Publishing Ltd
01-01-2022
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | 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 37 ka in a transect of sites from 19° 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 50 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 from 21° to 27°N were near late Holocene levels during the LGM time slice, suggesting a more muted LGM response than observed from 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.
Plain Language Summary
Dust that is picked up by winds over North Africa and blown out into the Atlantic Ocean can tell us about climate change in the past, particularly about variations in wind strength and location, and how wet the continent was. This study uses seafloor sediments from four sites offshore of West Africa to reconstruct how much dust was blown out from North Africa over the last 67,000 years. The records show that the climate of North Africa is controlled by two major processes: changes to incoming energy from the sun on timescales of thousands of years, and the extent of cold conditions in the high latitudes of the North Atlantic region on timescales of hundreds of years. We find a time from 60,000 to 50,000 years ago of low dust export (weak winds and a wet continent) when incoming energy from the sun was high, with dust levels similar to those during the Green Sahara interval that occurred 11,000 to 5,000 years ago. This time of low dust export was interrupted around 54,500 years ago by a brief interval of extremely high dust export (strong winds and a dry continent) during a North Atlantic cold interval called Heinrich event 5a.
Key Points
Coherent dust flux changes along the NW African margin and in the central North Atlantic over the last 67 ka
Abrupt dust flux variations on millennial timescales similar to N Atlantic stadials related to high‐latitude forcing of African climate
Green Sahara interval (60–50 ka) recorded by low dust fluxes to ODP 658C showing an orbitally forced strengthening of monsoon during MIS 3 |
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| ISSN: | 2572-4517 2572-4525 |
| DOI: | 10.1029/2020PA004137 |