Holocene dust records from the West African Sahel and their implications for changes in climate and land surface conditions

We reconstructed aeolian dust accumulation during the Holocene from two radiocarbon‐dated lake‐sediment sequences from the Manga Grasslands in northeastern Nigeria in order to investigate long‐term changes in the Harmattan dust system over West Africa and evaluate their possible causes. Flux values...

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Bibliographic Details
Published in:Journal of geophysical research. Atmospheres 2014-07, Vol.119 (14), p.8684-8694
Main Authors: Cockerton, Helen E., Holmes, Jonathan A., Street-Perrott, F. Alayne, Ficken, Katherine J.
Format: Article
Language:English
Subjects:
Climate
Climate change
Dunes
Dust
Dust control
Eolian dust
Floodplains
Fluctuations
Flux
Fluxes
Geophysics
Grasslands
Holocene
Human
Lake sediments
Lakes
Marine
Sediments
West Africa
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Summary:We reconstructed aeolian dust accumulation during the Holocene from two radiocarbon‐dated lake‐sediment sequences from the Manga Grasslands in northeastern Nigeria in order to investigate long‐term changes in the Harmattan dust system over West Africa and evaluate their possible causes. Flux values were low in the early Holocene, decreasing further to a minimum at around 6.2 kyr B.P. after which time they increased, steadily until around 2 kyr B.P. and then more sharply after this time. The long‐term variations in dust flux agree broadly with changes in the exposed area of the Lake Chad Basin to the northeast of the study sites, which vary inversely with the volume of Paleolake Megachad. More proximal sources of dust, including the fine fraction of local dune sand and floodplains of nearby rivers, have also made a contribution to the total dust load during times of enhanced dune and fluvial activity. Sharp rises in dust flux over the past century may be related to human activity. Broad patterns of change in dust flux during the Holocene agree with other reconstructions over the same period. However, we see no evidence for a stepped rise during the middle Holocene, as seen at some sites from the northeastern tropical Atlantic, suggesting that controls on the Harmattan dust system have differed from those affecting dust deposition elsewhere across northern Africa. Key Points Holocene dust fluxes reconstructed from lake sediments at two sites in West AfricaLow fluxes in early Holocene followed by rise from around 2 kyr B.P.Fluxes controlled by climate, sediment availability, and latterly human activity
ISSN:2169-897X
2169-8996
DOI:10.1002/2013JD021283