Sources, transport and deposition of terrestrial organic material: A case study from southwestern Africa

Herrmann, Nicole; Boom, Arnoud; Carr, Andrew S.; Chase, Brian M.; Granger, Robyn; Hahn, Annette; Zabel, Matthias; Schefuß, Enno

doi:10.1016/j.quascirev.2016.07.028

Cited by 36 publications

(42 citation statements)

References 85 publications

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“…Studies within this region as well as in other areas of Africa revealed that these vegetation types showed differences in their nalkane composition (Rommerskirchen et al, 2006;Vogts et al, 2009;Carr, 2012Herrmann et al, 2016; map in Fig. 2).…”

Section: Vegetation In the Study Areamentioning

confidence: 88%

Southern Hemisphere anticyclonic circulation drives oceanic and climatic conditions in late Holocene southernmost Africa

et al. 2017

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Abstract. Due to the high sensitivity of southern Africa to climate change, a reliable understanding of its hydrological system is crucial. Recent studies of the regional climatic system have revealed a highly complex interplay of forcing factors on precipitation regimes. This includes the influence of the tropical easterlies, the strength of the southern hemispheric westerlies as well as sea surface temperatures along the coast of the subcontinent. However, very few marine records have been available in order to study the coupling of marine and atmospheric circulation systems. Here we present results from a marine sediment core, recovered in shallow waters off the Gouritz River mouth on the south coast of South Africa. Core GeoB18308-1 allows a closer view of the last ∼ 4 kyr. Climate sensitive organic proxies, like the distribution and isotopic composition of plant-wax lipids as well as indicators for sea surface temperatures and soil input, give information on oceanographic and hydrologic changes during the recorded time period. Moreover, the micropaleontology, mineralogical and elemental composition of the sediments reflect the variability of the terrigenous input to the core site. The combination of down-core sediment signatures and a catchment-wide provenance study indicate that the Little Ice Age (∼ 300-650 cal yr BP) was characterized by climatic conditions favorable to torrential flood events. The Medieval Climate Anomaly (∼ 950-650 cal yr BP) is expressed by lower sea surface temperatures in the Mossel Bay area and humid conditions in the Gouritz River catchment.These new results suggest that the coincidence of humid conditions and cooler sea surface temperatures along the south coast of South Africa resulted from a strengthened and more southerly anticyclonic circulation. Most probably, the transport of moisture from the Indian Ocean by strong subtropical easterlies was coupled with Agulhas Bank upwelling pulses, which were initiated by an increase in Agulhas Current strength.

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Section: Vegetation In the Study Areamentioning

confidence: 88%

Southern Hemisphere anticyclonic circulation drives oceanic and climatic conditions in late Holocene southernmost Africa

et al. 2017

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“…The Atlantic regime, which spans along the western and northern coasts, is characterized by high precipitation of more than 800 mm during winter. It is associated with the westerly wind belt at the Iberian Peninsula (Zorita et al, 1992) and to a large extent controlled by the NAO winter conditions (Hernández et al, 2015;Hurrell, 1995). During positive NAO conditions (i.e.…”

Section: Study Areamentioning

confidence: 99%

“…Under modern conditions the NAO is responsible for much of the variability in winter precipitation at the Iberian Peninsula (Hurrell, 1995;Zorita et al, 1992). Many paleo-climatic studies provide evidence for NAO-like climate variability since the mid-Holocene (Abrantes et al, 2017;Deininger et al, 2017;Olsen et al, 2012).…”

Section: Potential Drivers Of Terrestrial and Oceanic Climate Variabimentioning

confidence: 99%

“…Deininger et al, 2017;Wassenburg et al, 2016). The NAO is the dominant driver for the modern precipitation distribution in the western Mediterranean and particularly active during winter (Hurrell, 1995). Another potential driving mechanism, not only of the oceanic variability, is the cyclical Bond events (Bond et al, 1997), which are believed to weaken the thermohaline oceanic circulation and associated northward heat transport, and are thus responsible for cooling of the Northern Hemisphere (Bond et al, 2001;Wanner et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

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Multi-decadal atmospheric and marine climate variability in southern Iberia during the mid- to late-Holocene

et al. 2019

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Abstract. To assess the regional multi-decadal to multi-centennial climate variability along the southern Iberian Peninsula during the mid- to late-Holocene record of paleo-environmental indicators from marine sediments were established for two sites in the Alboran Sea (ODP-161-976A) and the Gulf of Cádiz (GeoB5901-2). High-resolution records of organic geochemical properties and planktic foraminiferal assemblages are used to decipher precipitation and vegetation changes as well as hydrological conditions with respect to sea surface temperature (SST) and marine primary productivity (MPP). As a proxy for precipitation change, records of plant-derived n-alkane composition suggest a series of five distinct dry episodes in southern Iberia at 5.4±0.3 ka cal BP, from 5.1 to 4.9±0.1 ka cal BP, from 4.8 to 4.7±0.1 ka cal BP, from 4.4 to 4.3±0.1 ka cal BP, and at 3.7±0.1 ka cal BP. During each dry episode the vegetation suffered from reduced water availability. Interestingly, the dry phase from 4.4 to 4.3±0.1 ka cal BP is followed by a rapid shift towards wetter conditions revealing a more complex pattern in terms of its timing and duration than was described for the 4.2 ka event in other regions. The series of dry episodes as well as closely connected hydrological variability in the Alboran Sea were probably driven by NAO-like (North Atlantic Oscillation) variability. In contrast, surface waters in the Gulf of Cádiz appear to have responded more directly to North Atlantic cooling associated with Bond events. In particular, during Bond events 3 and 4, a pronounced increase in seasonality with summer warming and winter cooling is found.

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“…C values of bulk POC and plant-wax biomarkers contained in fluvial suspended sediments during transit have been observed in both the Ganges-Brahmaputra (Galy et al, 2008b and Orange Rivers (Herrmann et al, 2016), likely due to overprinting of headwater material with downstream sources. Similarly, downstream decreases in bulk 13 C composition and carbon-normalized lignin concentration in Amazon River fine-grained POC have been attributed to the addition of floodplain soil material (Hedges et al, 1986(Hedges et al, , 2000b.…”

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confidence: 99%

Understanding terrestrial organic carbon export : a time-series approach

Hemingway¹

2017

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Sources, transport and deposition of terrestrial organic material: A case study from southwestern Africa

Cited by 36 publications

References 85 publications

Southern Hemisphere anticyclonic circulation drives oceanic and climatic conditions in late Holocene southernmost Africa

Southern Hemisphere anticyclonic circulation drives oceanic and climatic conditions in late Holocene southernmost Africa

Multi-decadal atmospheric and marine climate variability in southern Iberia during the mid- to late-Holocene

Understanding terrestrial organic carbon export : a time-series approach

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