Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years (original) (raw)
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Comment on "Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years
Science, 2008
Kröpelin et al . (Research Articles, 9 May 2008, p. 765) interpreted a sediment record from Lake Yoa in the east-central part of North Africa as support for a weak biogeophysical climate-vegetation feedback in the Sahara during the mid-Holocene. We argue that the new data do not invalidate earlier modeling results on strong land-atmosphere coupling in the Western Sahara for which the Lake Yoa record is far less representative.
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2022
The climate history of the Sahara desert during recent millennia is obscured by the near absence of natural climate archives, hampering insight in the relative importance of southerly (tropical) and northerly (midlatitude) weather systems at submillennial time scales. A new lake sediment record from Ounianga Serir oasis in northern Chad, spanning the Late Holocene without interruption, confirms that immediately before ca 4200 years ago, the Sahara experienced an episode of hyperaridity even more extreme than today's desert climate. The hypersaline terminal lake which formed afterwards never desiccated during the late Holocene due to continuous inflow of fossil groundwater, yet its water balance was sensitive to temporal variation in local rainfall and lake surface evaporation. Our in-lake geochemical proxies show that, during the last 3000 years, century-scale hydroclimate variation in the central Sahara primarily tracked the intensity of the tropical West African monsoon, modulated at shorter time scales by weather patterns linked to shifts in midlatitude Atlantic Ocean circulation.
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Early Holocene greening of the Sahara requires Mediterranean winter rainfall
Proceedings of the National Academy of Sciences, 2021
Significance Explaining the greening of the Sahara during the Holocene has been a challenge for decades. A strengthening of the African monsoon caused by increased summer insolation is usually cited to explain why the Sahara was vegetated from 14,000 to 5,000 y ago. Here, we provide a unique climate record of quantified winter, spring, and summer precipitation in Morocco over the past 18,500 y, and numeric simulations, which show that moisture contributions from the Mediterranean Sea and the North Atlantic Ocean in winter, were as important as the expanded summer monsoon for the greening of the Sahara during the African humid period. The findings of this study will help to better understand and simulate climate variability over northern Africa.
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The climate of the Sahara in the period of meteorological records
In Allan, J. A. (ed.), The Sahara, Ecological Change and Early Economic History , Menas Press Ltd., London, 1981
Concerns mainly precipitation, in a region where mean annual values are less than 150 mm in the south and less than 100 mm in the north, and where rainfall is highly variable from year to year and over short distances. The work of climatologists published since the beginning of the century is reviewed and the attempts to discern some kind of ordering of the rainfall experienced in the north and south sides of the Sahara are assessed. It is concluded that a complexity exists in the precipitation departure patterns over northern Africa giving a large number of anomaly types. The anomalous conditions are relevant with respect to the possibility of a temporary existence of lakes in the Late Holocene
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