Late Quaternary Hydrologic Changes in the Arid and Semiarid Belt of Northern Africa

Gasse, Françoise; Roberts, C. Neil

doi:10.1007/978-1-4020-2944-8_12

Cited by 67 publications

(47 citation statements)

References 55 publications

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“…In southern Africa, including at least parts of the Congo basin, dry conditions persisted beyond the end of the YD, the climate only achieving typical Holocene-like levels of humidity at circa 10 ka ( Figure 5). North of the equator, on the other hand, the transition was much more rapid with notably humid conditions reaching arid northern Africa within a few hundred years of the end of the YD (Figure 6) [Gasse and Roberts, 2005]. Eventually, this change pushed the northern limit of the ITCZ several 100 km into the heart of northern Africa; Gasse and Roberts [2005] estimate that at its maximum early Holocene extent the ITCZ lay around 3°-5°north of its present mean position.…”

Section: Discussionmentioning

confidence: 97%

“…North of the equator, on the other hand, the transition was much more rapid with notably humid conditions reaching arid northern Africa within a few hundred years of the end of the YD (Figure 6) [Gasse and Roberts, 2005]. Eventually, this change pushed the northern limit of the ITCZ several 100 km into the heart of northern Africa; Gasse and Roberts [2005] estimate that at its maximum early Holocene extent the ITCZ lay around 3°-5°north of its present mean position. At the southern margin of the monsoon belt, on the other hand, a corresponding northward translation of the southern limit of the ITCZ initially put Lake Malawi mainly beyond the limit of monsoon rains, leaving it under the influence of the dry SE Trades, possibly for much of the year.…”

Section: Discussionmentioning

confidence: 97%

“…[5] Although direct or proxy evidence of climatically driven changes in lake level have provided the most widespread evidence of past climate change in tropical Africa [Street-Perrott and Perrott, 1993;Gasse, 2000;Barker and Gasse, 2003;Barker et al, 2004;Hoelzmann et al, 2004;Gasse and Roberts, 2005], most lakes in the region, particularly large, deep water bodies, are also sensitive to variations in wind regime. Primary production in many of the larger lakes is dependent upon nutrient regeneration in the epilimnion, and subsequent return by vertical mixing of the regenerated nutrients into the photic zone.…”

Section: Paleowind Records From African Lakesmentioning

confidence: 99%

“…Of particular note is the very abrupt decline in terrigenous flux at 11.6 ka (Figure 4). Although some of this decrease must have been due to increasing vegetation cover on the adjacent continent [deMenocal et al, 2000;Hoelzmann et al, 2004;Gasse and Roberts, 2005], it may also reflect an abrupt decline in the transport capacity of the winds blowing off the continent. This change may in part have been due to generally lower wind velocities, but could also be a consequence of greater northward penetration of the ITCZ reducing the seasonal influence of the NE Trades.…”

Section: North Of the Equatormentioning

confidence: 99%

“…[22] Across the Sahel and Sahara, and in Ethiopia, a major phase of lake filling commenced between circa 11.5 and 11.2 ka [Gasse, 2000;Chalié and Gasse, 2002;Gasse and Roberts, 2005;Hoelzmann et al, 2004]. Prior to this, many basins were desiccated or contained saline water bodies.…”

Section: Northern Tropical Africamentioning

confidence: 99%

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An abrupt change in the African monsoon at the end of the Younger Dryas

Talbot

Filippi

Jensen

et al. 2007

Geochem Geophys Geosyst

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[1] High-resolution studies of variations in the elemental and stable carbon-and nitrogen-isotope composition of organic matter in cores from Lakes Malawi, Tanganyika, and Bosumtwi (tropical Africa) indicate an abrupt change in the wind-driven circulation of these lakes that, within the limits of available chronologies, was contemporaneous with the end of the Younger Dryas in the northern hemisphere. The change was also coincident with shifts in surface winds recorded in cores from off the west and northeast coasts of Africa. A range of other proxies indicate that these changes in wind regime were accompanied by a marked increase in precipitation in the northern tropics. Africa south of 5°-10°S, on the other hand, initially suffered drought conditions. Together, the evidence suggests an abrupt northward translation of the African monsoon system at circa 11.5 ± 0.25 ka B.P. The data assembled here contribute to a growing body of work showing that the Younger Dryas was a major climatic excursion in tropical Africa. Furthermore, they add substance to recent suggestions that climatic events in the southern hemisphere may have played a significant role in the abrupt demise of the Younger Dryas.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 97%

Section: Paleowind Records From African Lakesmentioning

confidence: 99%

Section: North Of the Equatormentioning

confidence: 99%

Section: Northern Tropical Africamentioning

confidence: 99%

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An abrupt change in the African monsoon at the end of the Younger Dryas

Talbot

Filippi

Jensen

et al. 2007

Geochem Geophys Geosyst

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Seasonal and ENSO Influences on the Stable Isotopic Composition of Galápagos Precipitation

et al. 2018

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The origin of stable isotopic variability in precipitation over time and space is critical to the interpretation of stable isotope‐based paleoclimate proxies. In the eastern equatorial Pacific, modern stable isotope measurements in precipitation (δ18Op and δDp) are sparse and largely unevaluated in the literature, although insights from such analyses would benefit the interpretations of several regional isotope‐based paleoclimate records. Here we present a new 3.5 year record of daily‐resolved δ18Op and δDp from Santa Cruz, Galápagos. With a prior 13 year record of monthly δ18Op and δDp from the island, these new data reveal controls on the stable isotopic composition of regional precipitation on event to interannual time scales. Overall, we find Galápagos δ18Op is significantly correlated with precipitation amount on daily and monthly time scales. The majority of Galápagos rain events are drizzle, or garúa, derived from local marine boundary layer vapor, with corresponding high δ18Op values due to the local source and increased evaporation and equilibration of smaller drops with boundary layer vapor. On monthly time scales, only precipitation in very strong, warm season El Niño months has substantially lower δ18Op values, as the sea surface temperature threshold for deep convection (28°C) is only surpassed at these times. The 2015/2016 El Niño event did not produce strong precipitation or δ18Op anomalies due to the short period of warm SST anomalies, which did not extend into the peak of the warm season. Eastern Pacific proxy isotope records may be biased toward periods of high rainfall during strong to very strong El Niño events.

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