Late Quaternary highstands at Lake Chilwa, Malawi: Frequency, timing and possible forcing mechanisms in the last 44ka

Thomas, David S.G.; Bailey, Richard M.; Shaw, Paul; Durcan, Julie A.; Singarayer, Joy

doi:10.1016/j.quascirev.2008.10.023

Cited by 79 publications

(59 citation statements)

References 62 publications

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“…This synchronicity supports our conclusion that the plant waxes are not transported over long distances. As suggested by other studies [8][9][10] , rainfall during HS1 and the YD likely also increased in the western parts of the Zambezi catchment. However, plant waxes derived from these more inland parts would carry a much more depleted δD signal due to increased moisture rainout during long-distance transport 29 .…”

supporting

confidence: 73%

“…Such interpretations are based on meteorological observations that modern rainfall in eastern and southern Africa is strongly related to high SST in the western and south-western Indian Ocean, respectively 7 . In contrast, Lake Chilwa located south-east of Lake Malawi, recorded high-stands, which appear to be solely associated with northern Hemisphere cold events 8 . Further westward in the interior of subtropical southern African, paleoenvironmental information is sparse.…”

mentioning

confidence: 81%

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Forcing of wet phases in southeast Africa over the past 17,000 years

Schefuß

Kuhlmann

Mollenhauer

et al. 2011

Nature

248

215

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Climate changes reconstructed from Lake Malawi, the southernmost of the East African Great Lakes and located within the Zambezi catchment, point to arid conditions and strong northerly wind anomalies during Northern Hemisphere cold events such as the Younger Dryas (YD) 2,3 . It has been inferred that these periods represent southward shifts of the ITCZ 2,3,6 . Dry conditions during the YD and Heinrich Stadial 1 (HS1) in Lake Tanganyika, located closer to the equator in East Africa, were interpreted to have been caused by lowered Indian Ocean SST 4 . Recently, widespread drought conditions during HS1 in East Africa have similarly been suggested to be driven by cold conditions in the Indian Ocean 5 . Such interpretations are based on meteorological observations that modern rainfall in eastern and southern Africa is strongly related to high SST in the western and south-western Indian Ocean, respectively 7 . In contrast, Lake Chilwa located south-east of Lake Malawi, recorded high-stands, which appear to be solely associated with northern Hemisphere cold events 8 . Further westward in the interior of subtropical southern African, paleoenvironmental information is sparse. Age dating of dunes in western Zambia and western Zimbabwe points to dry conditions at 18-17,000, 15-14,000, 11-8,000, and 6-4,000 years 9 before present (BP) implying that non-dune building periods around 16,000 and from 13-12,000 years BP roughly correspond to the wet periods found at Lake Chilwa 8 . Paleo-shorelines and other geomorphologic evidence from the Central Kalahari point to the existence of an extended lake system around the time of During austral winter a high pressure system over southern Africa leads to dry conditions, except in a small winter rainfall zone at its south-western tip 6 . The Zambezi River is the fourth-largest river in Africa originating in Zambia and flowing south-eastward to the Indian Ocean. The upper Zambezi is separated from its lower part by the Victoria Falls. After flowing through a series of gorges, the river enters a broad valley and spreads out over a large floodplain in its lower part. About 150 km from the coast, the catchment narrows where the river flows through the eastern Rift mountains. Maximum rainfall in the catchment during the peak of the southward ITCZ migration occurs in this area 12 (Fig. 1b), periodically causing extensive flooding 13 .The floodplain is dominated by papyrus swamps (dominated by Cyperus papyrus, a C 4 plant) with lower importance of reed swamps (Phragmites and Typha, C 3 plants) 14 . 4 The C 4 plant dominance in the lower Zambezi floodplain is seen in the relative abundance of C 4 plants (Fig. 1c, d) 15 . Downstream from the Rift mountains, the Zambezi splits up into a flat and wide delta 13 . Woodlands, savannah and extensive mangrove forests (C 3 plants) vegetate the delta and coastal areas 14 .The 6.51 m long marine sediment core GeoB9307-3 (18°33.9'S, 37°22.8'E, 542 m water depth) was retrieved about 100 km off the Zambezi delta. The core location is in the zone of high deg...

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supporting

confidence: 73%

mentioning

confidence: 81%

Forcing of wet phases in southeast Africa over the past 17,000 years

Schefuß

Kuhlmann

Mollenhauer

et al. 2011

Nature

248

215

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“…(d) Lake Malawi C 28 δD (Konecky et al, 2011). (e) Lake Chilwa OSL dates of shoreline (Thomas et al, 2009). (f) Wonderkrater reconstructed paleoprecipitation, PWetQ (precipitation of the wettest quarter; Truc et al, 2013).…”

Section: Regional Comparisonsmentioning

confidence: 99%

Three distinct Holocene intervals of stalagmite deposition and nondeposition revealed in NW Madagascar, and their paleoclimate implications

et al. 2017

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Abstract. Petrographic features, mineralogy, and stable isotopes from two stalagmites, ANJB-2 and MAJ-5, respectively from Anjohibe and Anjokipoty caves, allow distinction of three intervals of the Holocene in NW Madagascar. The Malagasy early Holocene (between ca. 9.8 and 7.8 ka) and late Holocene (after ca. 1.6 ka) intervals (MEHI and MLHI, respectively) record evidence of stalagmite deposition. The Malagasy middle Holocene interval (MMHI, between ca. 7.8 and 1.6 ka) is marked by a depositional hiatus of ca. 6500 years.Deposition of these stalagmites indicates that the two caves were sufficiently supplied with water to allow stalagmite formation. This suggests that the MEHI and MLHI intervals may have been comparatively wet in NW Madagascar. In contrast, the long-term depositional hiatus during the MMHI implies it was relatively drier than the MEHI and the MLHI.The alternating wet-dry-wet conditions during the Holocene may have been linked to the long-term migrations of the Intertropical Convergence Zone (ITCZ). When the ITCZ's mean position is farther south, NW Madagascar experiences wetter conditions, such as during the MEHI and MLHI, and when it moves north, NW Madagascar climate becomes drier, such as during the MMHI. A similar wetdry-wet succession during the Holocene has been reported in neighboring locations, such as southeastern Africa. Beyond these three subdivisions, the records also suggest wet conditions around the cold 8.2 ka event, suggesting a causal relationship. However, additional Southern Hemisphere highresolution data will be needed to confirm this.

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“…Meridional repositioning of the Intertropical Convergence Zone (ITCZ), the primary source of rainfall in most of the tropics, is thought to have been a major source of hydrological variability during the late Quaternary (1)(2)(3)(4). For example, ice sheet expansion forced the mean latitudinal position of the ITCZ southward along with other atmospheric circulation systems in the northern hemisphere during the Last Glacial Maximum (3), and abrupt North Atlantic cooling during deglacial melting and ice-rafting episodes such as Heinrich Stadial 1 (HS-1), along with associated reductions of marine meridional overturning circulation (MOC), is also thought to have had a similar effect on rain belts associated with the ITCZ (1,3,4).…”

mentioning

confidence: 99%

“…For example, ice sheet expansion forced the mean latitudinal position of the ITCZ southward along with other atmospheric circulation systems in the northern hemisphere during the Last Glacial Maximum (3), and abrupt North Atlantic cooling during deglacial melting and ice-rafting episodes such as Heinrich Stadial 1 (HS-1), along with associated reductions of marine meridional overturning circulation (MOC), is also thought to have had a similar effect on rain belts associated with the ITCZ (1,3,4). Some model simulations of northern hemisphere climatic changes associated with HS-1 indicate a southward drift of up to 10 latitudinal degrees (2).…”

mentioning

confidence: 99%