Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years

Kröpelin, Stefan; Verschuren, Dirk; Lézine, Anne-Marie; Eggermont, Hilde; Cocquyt, Christine; Francus, Pierre; Cazet, Jean-Pierre; Fagot, Maureen; Rumes, B.; Russell, J. M.; Darius, Frank; Conley, Daniel J.; Schuster, Mathieu; Suchodoletz, Hans von; Engstrom, D. R.

doi:10.1126/science.1154913

Cited by 593 publications

(482 citation statements)

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“…This shift is synchronous with an increase in aridity seen in the Sahel and Sahara in the mid Holocene in palaeo-records of the African monsoon from the western Atlantic Ocean (deMenocal et al, 2000). This mid Holocene change in the North African monsoon regime has been described in many studies (Servant and Servant-Vildary, 1980;Gasse and Van campo, 1994;Petit-Maire et al, 1997;Kropelin et al, 2008) and extends also to East Africa (see references in Gasse, 2000;Vincens et al, 2005). Mid-Holocene monsoon changes are also observed in the Arabian Sea area (Fleitmann et al, 2003;Fleitmann et al, 2007), the Tibetan Plateau (Gasse et al, 1991), and in Eastern Asia .…”

Section: Relationship Between the Australian Summer Monsoon And Othermentioning

confidence: 89%

Past dynamics of the Australian monsoon: precession, phase and links to the global monsoon concept

et al. 2010

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Past variations in the dynamics of the Australian monsoon have been estimated from multi-proxy analysis of a core retrieved in the Eastern Banda Sea. Records of coccolith and pollen assemblages, spanning the last 150 000 years, allow reconstruction of past primary production in the Banda Sea, summer moisture availability, and the length of the dry season in northern Australia and southeastern Indonesia. The amount of moisture available during the summer monsoon follows typical glacial/interglacial dynamics with a broad asymmetrical 100-kyr cycle. Primary production and length of the dry season appear to be closely related, given that they follow the precessional cycle with the same phase. This indicates their independence from ice-volume variations. The present inter-annual variability of both parameters is related to El Niño Southern Oscillation (ENSO), which modulates the Australian Winter Monsoon (AWM). The precessional pattern observed in the past dynamics of the AWM is found in ENSO and monsoon records of other regions. A marked shift in the monsoon intensity occurring during the mid Holocene during a period of constant ice volume, suggests that low latitude climatic variation precedes increases in global ice volume. This precessional pattern suggests that a common forcing mechanism underlies low latitude climate dynamics, acting specifically and synchronously on the different monsoon systems

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Section: Relationship Between the Australian Summer Monsoon And Othermentioning

confidence: 89%

Past dynamics of the Australian monsoon: precession, phase and links to the global monsoon concept

et al. 2010

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“…For example, dust output from the Sahara presently varies between 400 and 700 10 12 g yr 21 , a value that accounts for ,50% of the global atmospheric dust budget (Pulido-Villena et al 2006). However, fossil studies suggest that particle loading to the atmosphere (deflation) may have been substantially greater around 4300 yr B.P., when desiccation of North Africa reduced vegetation cover and increased erosive activity of winds (Krö pelin et al 2008). As speculated elsewhere, redeposition of Ca-rich Saharan dust may represent a significant influx of nutrients to alpine lakes, where weathering has previously depleted catchment stores of this element (Psenner 1999).…”

Section: Fossil Evidence Of Climate Effects On Lakesmentioning

confidence: 99%

Paleolimnological evidence of the effects on lakes of energy and mass transfer from climate and humans

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et al. 2009

Limnology & Oceanography

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The premise of this article is that climate effects on lakes can be quantified most effectively by the integration of process-oriented limnological studies with paleolimnological research, particularly when both disciplines operate within a common conceptual framework. To this end, the energy (E)-mass (m) flux framework (Em flux) is developed and applied to selected retrospective studies to demonstrate that climate variability regulates lake structure and function over diverse temporal and spatial scales through four main pathways: rapid direct transfer of E to the lake surface by irradiance, heat, and wind; slow indirect effects of E via changes in terrestrial development and subsequent m subsidies to lakes; direct influx of m as precipitation, particles, and solutes from the atmosphere; and indirect influx of water, suspended particles, and dissolved substances from the catchment. Sedimentary analyses are used to illustrate the unique effects of each pathway on lakes but suggest that interactions among mechanisms are complex and depend on the landscape position of lakes, catchment characteristics, the range of temporal variation of individual pathways, ontogenetic changes in lake basins, and the selective effects of humans on m transfers. In particular, preliminary synthesis suggests that m influx can overwhelm the direct effects of E transfer to lakes, especially when anthropogenic activities alter m subsidies from catchments.The structure and function of lake ecosystems is regulated by complex interactions among climate, humans, ecosystem morphology, and catchment characteristics, each of which varies in time and space (Schindler 2001). For example, climatic controls range from daily meteorological variations in local irradiance, temperature, and water fluxes (Keller 2007) through to large-scale interactions of the atmosphere and oceans (Trenberth and Hurrell 1994;Hurrell 1995;Mantua et al. 1997) and millennium-long changes in energy (E) and mass (m) flux around the planet (Williams et al. 1997;Diffenbaugh et al. 2006). Within this framework, chemical, physical, and ecological processes combine to determine the production and composition of aquatic communities, both uniquely and in consort with other mechanisms (Carpenter 1999). In addition, lakes are affected both by human disturbance of biotic communities and biogeochemical cycles (e.g., land use, urbanization, fisheries management) and by creation of novel stressors (e.g., acidic precipitation, toxicants, ozone loss). However, because these factors interact over diverse spatial and temporal scales, it is difficult to determine the relative importance of regulatory processes using only traditional site-based observation and experimentation. Instead, it is the premise of this article that the combined use of limnology and paleoecology represents the best means to quantify and scale interactions between climate and other control mechanisms and to develop a hierarchical understanding of how these regulatory processes are likely to influence lakes pres...

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“…2; Berke et al 2012a; Gasse 2000; Kröpelin et al 2008;Mayewski et al 2004). In the Turkana region, the termination was abrupt, but the magnitude of the drop was within the scope of fluctuating lake levels that occurred during the EMH (Bloszies et al in press;Forman et al 2014).…”

Section: Archaeological Evidence Within the Context Of Regional Climamentioning

confidence: 99%

Lakeside View: Sociocultural Responses to Changing Water Levels of Lake Turkana, Kenya

et al. 2015

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Throughout the Holocene, Lake Turkana has been subject to drastic changes in lake levels and the subsistence strategies people employ to survive in this hot and arid region. In this paper, we reconstruct the position of the lake during the Holocene within a paleoclimatic context. Atmospheric forcing mechanisms are discussed in order to contextualize the broader landscape changes occurring in eastern Africa over the last 12,000 years. The Holocene is divided into five primary phases according to changes in the strand-plain evolution, paleoclimate, and human subsistence strategies practiced within the basin. Early Holocene fishing settlements occurred adjacent to high and relatively stable lake levels. A period of high-magnitude oscillations in lake levels Afr Archaeol Rev (2015) ensued after 9,000 years BP and human settlements appear to have been located close to the margins of the lake. Aridification and a final regression in lake levels ensued after 5,000 years BP and human communities were generalized pastoralists-fishers-foragers. During the Late Holocene, lake levels may have dropped below their present position and subsistence strategies appear to have been flexible and occasionally specialized on animal pastoralism. Modern missionary and government outposts have encouraged the construction of permanent settlements in the region, which are heavily dependent on outside resources for their survival. Changes in the physical and cultural environments of the Lake Turkana region have been closely correlated, and understanding the relationship between the two variables remains a vital component of archaeological research.Résumé Tout l'Holocène, le lac Turkana a été soumis à des changements drastiques dans l'altitude des lacs et les stratégies de subsistance des gens utilisent pour survivre dans cette région chaude et aride. Dans cet article, nous reconstruisons la position du lac au cours de l'Holocène dans un contexte paléoclimatique. Mécanismes de forçage atmosphériques sont discutées afin de contextualiser les changements de paysage plus larges qui se produisent en Afrique orientale au cours des 12.000 dernières années. L'Holocène est divisé en cinq phases principales en fonction des changements dans l'évolution altitude du lac, paléoclimats et les stratégies de subsistance humains pratiqués dans le bassin. Premiers établissements de pêche de l'Holocène ont eu lieu à proximité d'altitude d'eau élevés et relativement stables. Une période d'oscillations de grande amplitude dans l'altitude du lac s'ensuit après 9000 années BP et les établissements humains semblent avoir été situé à proximité des marges sur le lac. Aridification et une régression finale du altitude des lacs s'ensuit après 5000 années BP et les communautés humaines sont généralisées éleveurs-pêcheurs-cueilleurs. Au cours de l'Holocène tardif, les altitudes des lacs pourraient avoir chuté en dessous de leur position actuelle et les stratégies de subsistance semblent avoir fait preuve de souplesse et de temps en temps spécialisé sur le pas...

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Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years

Cited by 593 publications

References 40 publications

Past dynamics of the Australian monsoon: precession, phase and links to the global monsoon concept

Past dynamics of the Australian monsoon: precession, phase and links to the global monsoon concept

Paleolimnological evidence of the effects on lakes of energy and mass transfer from climate and humans

Lakeside View: Sociocultural Responses to Changing Water Levels of Lake Turkana, Kenya

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