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A potential human footprint on Western Central African rainforests before the Common Era has become the focus of an ongoing controversy. Between 3,000 y ago and 2,000 y ago, regional pollen sequences indicate a replacement of mature rainforests by a forest-savannah mosaic including pioneer trees. Although some studies suggested an anthropogenic influence on this forest fragmentation, current interpretations based on pollen data attribute the ''rainforest crisis'' to climate change toward a drier, more seasonal climate. A rigorous test of this hypothesis, however, requires climate proxies independent of vegetation changes. Here we resolve this controversy through a continuous 10,500-y record of both vegetation and hydrological changes from Lake Barombi in Southwest Cameroon based on changes in carbon and hydrogen isotope compositions of plant waxes. [Formula: see text] 13 C-inferred vegetation changes confirm a prominent and abrupt appearance of C 4 plants in the Lake Barombi catchment, at 2,600 calendar years before AD 1950 (cal y BP), followed by an equally sudden return to rainforest vegetation at 2,020 cal y BP. [Formula: see text]D values from the same plant wax compounds, however, show no simultaneous hydrological change. Based on the combination of these data with a comprehensive regional archaeological database we provide evidence that humans triggered the rainforest fragmentation 2,600 y ago. Our findings suggest that technological developments, including agricultural practices and iron metallurgy, possibly related to the large-scale Bantu expansion, significantly impacted the ecosystems before the Common Era., Competing Interests: The authors declare no conflict of interest.

Intense debate persists about the climatic mechanisms governing hydrologic changes in tropical and subtropical southeast Africa since the Last Glacial Maximum, about 20,000 years ago. In particular, the relative importance of atmospheric and oceanic processes is not firmly established. Southward shifts of the intertropical convergence zone (ITCZ) driven by high-latitude climate changes have been suggested as a primary forcing, whereas other studies infer a predominant influence of Indian Ocean sea surface temperatures on regional rainfall changes. To address this question, a continuous record representing an integrated signal of regional climate variability is required, but has until now been missing. Here we show that remote atmospheric forcing by cold events in the northern high latitudes appears to have been the main driver of hydro-climatology in southeast Africa during rapid climate changes over the past 17,000 years. Our results are based on a reconstruction of precipitation and river discharge changes, as recorded in a marine sediment core off the mouth of the Zambezi River, near the southern boundary of the modern seasonal ITCZ migration. Indian Ocean sea surface temperatures did not exert a primary control over southeast African hydrologic variability. Instead, phases of high precipitation and terrestrial discharge occurred when the ITCZ was forced southwards during Northern Hemisphere cold events, such as Heinrich stadial 1 (around 16,000 years ago) and the Younger Dryas (around 12,000 years ago), or when local summer insolation was high in the late Holocene, that is, during the past 4,000 years.

The southwest of Morocco is considered to be an area of refuge within the Mediterranean region, hosting the endemic tropical Argan tree. This region is presently subject to severe droughts, desertification and land degradation, and likely facing increased climate variability and socio-economic stress in the future. Here, we use the stable hydrogen and carbon isotope composition (δD and δ13C) of plant-waxes in a high-resolution marine sediment core (GeoB8601-3) collected off Cape Ghir in southwestern Morocco, in combination with published data on pollen and XRF element ratios from the same archive. We aim to reconstruct the hydroclimate and vegetation history during the last 3000 years. Stable carbon isotope compositions of leaf waxes (δ13Cwax) show that natural vegetation in southwestern Morocco consists of C3 plants. Minor variations in δ13Cwax were positively correlated to changes in stable hydrogen isotope compositions of leaf waxes (δDwax) before 700 CE. Changes in rainfall amounts and water use efficiency indicate a clear vegetation response to precipitation changes and thus to climate forcing. After 700 CE, δDwax and δ13Cwax became de-coupled suggesting that the plant wax discharge and their isotope signals were no longer solely controlled by climate; the waxes likely mainly originate from the lowlands and carry an enriched (dry) δD signal but a depleted 13C signature. The depletion of δ13Cwax correlates with the increase of Argan pollen concentration in the record. The period between ~700 and 900 CE coincides with the Arabization of Morocco which had an impact on the demographic composition of the country leading to new agricultural habits and, as a result, on the land-use triggering a higher erosion of lowland material by the Souss River. [ABSTRACT FROM AUTHOR]

Terrestrial vegetation and soils hold three times more carbon than the atmosphere. Much debate concerns how anthropogenic activity will perturb these surface reservoirs, potentially exacerbating ongoing changes to the climate system. Uncertainties specifically persist in extrapolating point-source observations to ecosystemscale budgets and fluxes, which require consideration of vertical and lateral processes on multiple temporal and spatial scales. To explore controls on organic carbon (OC) turnover at the river basin scale, we present radiocarbon (14C) ages on two groups of molecular tracers of plant-derived carbon--leaf-wax lipids and lignin phenols--from a globally distributed suite of rivers. We find significant negative relationships between the 14C age of these biomarkers and mean annual temperature and precipitation. Moreover, riverine biospheric-carbon ages scale proportionally with basinwide soil carbon turnover times and soil 14C ages, implicating OC cycling within soils as a primary control on exported biomarker ages and revealing a broad distribution of soil OC reactivities. The ubiquitous occurrence of a long-lived soil OC pool suggests soil OC is globally vulnerable to perturbations by future temperature and precipitation increase. Scaling of riverine biosphericcarbon ages with soil OC turnover shows the former can constrain the sensitivity of carbon dynamics to environmental controls on broad spatial scales. Extracting this information from fluvially dominated sedimentary sequences may inform past variations in soil OC turnover in response to anthropogenic and/or climate perturbations. In turn, monitoring riverine OC composition may help detect future climate-change-induced perturbations of soil OC turnover and stocks. [ABSTRACT FROM AUTHOR]

We present a continuous and well-resolved record of climatic variability for the past 100 000 years from a marine sediment core taken in Delagoa Bight, off southeastern Africa. In addition to providing a sea surface temperature reconstruction for the past ca. 100 000 years, this record also allows a high-resolution continental climatic reconstruction. Climate sensitive organic proxies, like the distribution and isotopic composition of plant-wax lipids as well as elemental indicators of fluvial input and weathering type provide information on climatic changes in the adjacent catchment areas (Incomati, Matola and Lusutfu rivers). At the transition between glacials and interglacials, shifts in vegetation correlate with changes in sea surface temperature in the Agulhas Current. The local hydrology, however, does not follow these orbitally paced shifts. Instead, precipitation patterns follow millennial-scale variations with different forcing mechanisms in glacial vs. interglacial climatic states. During glacials, southward displacement of the Intertropical Convergence Zone facilitates a transmission of northern hemispheric signals (e.g., Heinrich events) to the southern hemispheric subtropics. Furthermore, the southern hemispheric westerlies become a more direct source of precipitation as they shift northward over the study site, especially during Antarctic cold phases. During interglacials, the observed short-term hydrological variability is also a function of Antarctic climate variability; however, it is driven by the indirect influence of the southern hemispheric westerlies and the associated South African high-pressure cell blocking the South Indian Ocean Convergence Zone related precipitation. As a consequence of the interplay of these effects, small-scale climatic zones exist. We propose a conceptual model describing latitudinal shifts of these zones along the southeastern African coast as tropical and temperate climate systems shift over glacial and interglacial cycles. The proposed model explains some of the apparent contradictions between several paleoclimate records in the region. [ABSTRACT FROM AUTHOR]

Biomass burning on the African continent is widespread, and interactions with climate, vegetation dynamics, and biogeochemical cycling are complex. To obtain a better understanding of these complex relationships, African fire history has been widely studied, although mostly on relatively short timescales (i.e., years to kiloyears) and less commonly on long‐term scales. Here we present a 192‐kyr, continuous biomass‐burning record from sub‐Saharan Northwest Africa based on the fire biomarker levoglucosan in a marine sediment core offshore Guinea. Notable features of our record include an increase in levoglucosan accumulation at 80 ka and two peaks at 50–60 ka. The event at 80 ka is likely related to an overall increase in sedimentation rates rather than an increase in biomass burning in the Northwest African savanna region. Our record indicates that glacial/interglacial changes in regional climate and vegetation composition (C3 vs. C4 plants) were not a major influence on biomass burning over the last 192 kyr. However, we suggest that the burning events at 50–60 ka might be caused by increased occurrence of C3 vegetation and human settlement in this region. At this time, the savanna region became wetter and fuel loads likely increased. Therefore, the region was more hospitable for humans, who likely used fire for hunting activities. Collectively, we hypothesize that on longer (glacial/interglacial) timescales, biomass burning, regional climate, and African vegetation are not necessarily coupled, while around 50–60 ka, higher fuel loads and human fire use may have influenced fire occurrence in sub‐Saharan Northwest Africa. Key Points: Biomass burning history of sub‐Saharan Northwest Africa during the last 192 kyr was studied, based on levoglucosan accumulation ratesGlacial/interglacial changes in regional climate and vegetation composition were not a major influence on biomass burningFire events around 50–60 ka in sub‐Saharan Northwest Africa might be caused by increased fuel loads and human fire use [ABSTRACT FROM AUTHOR]

Abstract There is increasing evidence that abrupt vegetation shifts and large-scale erosive phases occurred in Central Africa during the third millennium before present. Debate exists as to whether these events were caused by climate change and/or intensifying human activities related to the Bantu expansion. In this study, we report on a multi-proxy investigation of a sediment core (KZR-23) recovered from the Congo submarine canyon. Our aim was to reconstruct climate, erosion and vegetation patterns in the Congo Basin for the last 10,000 yrs, with a particular emphasis on the late Holocene period. Samples of modern riverine suspended particulates were also analyzed to characterize sediment source geochemical signatures from across the Congo watershed. We find that a sudden increase of bulk sediment aluminium-to-potassium (Al/K) ratios and initial radiocarbon ages of bulk organic matter occurred after 2,200 yrs ago, coincident with a pollen-inferred vegetation change suggesting forest retreat and development of savannas. Although hydrogen isotope compositions of plant waxes (δ D wax) do not reveal a substantial hydroclimate shift during this period, neodymium isotopes and rare earth elements in detrital fractions indicate provenance changes for the sediment exported from the Congo Basin at that time, hence suggesting a reorganization of spatial rainfall patterns across Central Africa during this event. Taken together, these findings provide evidence for changing landscapes in Central Africa from about 2,200 yrs ago, associated with synchronous events of vegetation changes and enhanced erosion of pre-aged and highly weathered soils. These events coincided remarkably well with the arrival of Iron Age communities into the rainforest, as inferred from comparison to regional archaeological syntheses. While the human impact on the environment remains difficult to quantify at the scale of the vast Congo Basin, we tentatively propose that strengthening of El Niño-Southern Oscillation (ENSO) variability at that time played a key role in triggering the observed environmental changes, and possibly acted as a driver for the eastward migration of Bantu-speaking peoples across Central Africa. Highlights • Major landscape reorganization in Central Africa from about 2,200 yrs ago. • Proxies indicate vegetation shift and erosion of pre-aged and highly weathered soils. • Synchronous period of climate instability related to enhanced ENSO variability. • Climate and human land-use were closely interconnected during the rainforest crisis. [ABSTRACT FROM AUTHOR]

Organic geochemical and micropaleontological analyses of surface sediments collected in the southern Drake Passage and the Bransfield Strait, Antarctic Peninsula, enable a proxy-based reconstruction of recent sea ice conditions in this climate sensitive area. The distribution of the sea ice biomarker IPSO25 supports earlier suggestions that the source diatoms seem to be common in near-coastal environments characterized by an annually recurring sea ice cover. We here propose and evaluate the combination of IPSO25 with a more unsaturated highly branched isoprenoid alkene and phytosterols and introduce the PIPSO25 index as a potentially semi-quantitative sea ice proxy. This organic geochemical approach is complemented with diatom data. PIPSO25 sea ice estimates are used to discriminate between areas characterized by permanently ice-free conditions, seasonal sea ice cover and extended sea ice cover. These trends are consistent with satellite sea ice data and winter sea ice concentrations estimated by diatom transfer functions. Minor offsets between proxy-based and satellite-based sea ice data are attributed to the different time intervals recorded within the sediments and the instrumental records from the study area, which experienced rapid environmental changes during the past 100 years. [ABSTRACT FROM AUTHOR]

Southwest Africa is an important region for paleo-climatic studies, being influenced by both tropical and temperate climate systems and thus reflecting the interplay of variable controls. The aim of this study was to unravel the interaction of sea-surface temperature (SST) changes in the southernmost Benguela upwelling system with precipitation changes in South Africa's winter rainfall zone (WRZ) during the late Holocene. Therefore, a marine sediment core from the southernmost Benguela upwelling system was investigated to reconstruct climate changes in this region for the past ~2000 years. Grain size and geochemical analyses were conducted to reconstruct changes in fluvial sediment discharge and weathering intensity, while SST changes were estimated using alkenone paleo-thermometry. Results show that the southernmost Benguela behaves distinctly in comparison with the rest of the Benguela system reflecting amplified SST changes. Decreasing SSTs accompanied increasing river discharge during times of increased precipitation in the WRZ, reflecting northerly shifted westerly winds during austral winter. We infer a control of past SST changes by processes not analogous to modern processes driving seasonal SST changes by changes through upwelling intensity. The findings suggest that late-Holocene SST changes in the southernmost Benguela upwelling system and the precipitation in the WRZ were both driven by latitudinal shifts of the austral westerly wind belt and associated changes in advection of cold sub-Antarctic waters and/or changes in Agulhas leakage of warm Indian Ocean waters. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

To better understand Holocene vegetation and hydrological changes in South Africa, we analyzed pollen and microcharcoal records of two marine sites GeoB8331 and GeoB8323 from the Namaqualand mudbelt offshore the west coast of South Africa covering the last 9900 and 2200 years, respectively. Our data corroborate findings from literature that climate developments apparently contrast between the summer rainfall zone (SRZ) and winter rainfall zone (WRZ) over the last 9900 years, especially during the early and middle Holocene. During the early Holocene (9900-7800 cal. yr BP), a minimum of grass pollen suggests low summer rainfall in the SRZ, and the initial presence of Renosterveld vegetation indicates relatively wet conditions in the WRZ. Toward the middle Holocene (7800-2400 cal. yr BP), a rather moist savanna/grassland rich in grasses suggests higher summer rainfall in the SRZ resulting from increased austral summer insolation and a decline of fynbos vegetation accompanied by an increasing Succulent Karoo vegetation in the WRZ, which possibly suggests a southward shift of the Southern Hemisphere westerlies. During the last 2200 years, a trend toward higher aridity was observed for the SRZ, while the climate in the WRZ remained relatively stable. The 'Little Ice Age' (ca. 700-200 cal. yr BP) was rather cool in both rainfall zones and drier in the SRZ while it was wetter in the WRZ. [ABSTRACT FROM AUTHOR]

Abstract: An isobathic transect of marine surface sediments from 1°N to 28°S off southwest Africa was used to further evaluate the potential of the chain length distribution and carbon stable isotope composition of higher plant n-alkanes as proxies for continental vegetation and climate conditions. We found a strong increase in the n-C29–33 weighted mean average δ13C values from −33‰ near the equator to around −26‰ further south. Additionally, C25–35 n-alkanes reveal a southward trend of increasing average chain length from 30.0 to 30.5. The data reflect the changing contribution of plants employing different photosynthetic pathways (C3 and C4) and/or being differently influenced by the environmental conditions of their habitat. The C4 plant proportions calculated from the data (ca. 20% for rivers draining the rainforest, to ca. 70% at higher latitude) correspond to the C4 plant abundance in continental catchment areas postulated by considering prevailing wind systems and river outflows. Furthermore, the C4 plant contribution to the sediments correlates with the mean annual precipitation and aridity at selected continental locations in the postulated catchment areas, suggesting that the C4 plant fraction in marine sediments can be used to assess these environmental parameters. [Copyright &y& Elsevier]

Intense debate persists about the climatic mechanisms governing hydrologic changes in tropical and subtropical southeast Africa since the Last Glacial Maximum, about 20,000?years ago. In particular, the relative importance of atmospheric and oceanic processes is not firmly established. Southward shifts of the intertropical convergence zone (ITCZ) driven by high-latitude climate changes have been suggested as a primary forcing, whereas other studies infer a predominant influence of Indian Ocean sea surface temperatures on regional rainfall changes. To address this question, a continuous record representing an integrated signal of regional climate variability is required, but has until now been missing. Here we show that remote atmospheric forcing by cold events in the northern high latitudes appears to have been the main driver of hydro-climatology in southeast Africa during rapid climate changes over the past 17,000 years. Our results are based on a reconstruction of precipitation and river discharge changes, as recorded in a marine sediment core off the mouth of the Zambezi River, near the southern boundary of the modern seasonal ITCZ migration. Indian Ocean sea surface temperatures did not exert a primary control over southeast African hydrologic variability. Instead, phases of high precipitation and terrestrial discharge occurred when the ITCZ was forced southwards during Northern Hemisphere cold events, such as Heinrich stadial 1 (around 16,000?years ago) and the Younger Dryas (around 12,000?years ago), or when local summer insolation was high in the late Holocene, that is, during the past 4,000?years. [ABSTRACT FROM AUTHOR]

Past hydrological changes in Africa have been linked to various climatic processes, depending on region and timescale. Long-term precipitation changes in the regions of northern and southern Africa influenced by the monsoons are thought to have been governed by precessional variations in summer insolation. Conversely, short-term precipitation changes in the northern African tropics have been linked to North Atlantic sea surface temperature anomalies, affecting the northward extension of the Intertropical Convergence Zone and its associated rainbelt. Our knowledge of large-scale hydrological changes in equatorial Africa and their forcing factors is, however, limited. Here we analyse the isotopic composition of terrigenous plant lipids, extracted from a marine sediment core close to the Congo River mouth, in order to reconstruct past central African rainfall variations and compare this record to sea surface temperature changes in the South Atlantic Ocean. We find that central African precipitation during the past 20,000 years was mainly controlled by the difference in sea surface temperatures between the tropics and subtropics of the South Atlantic Ocean, whereas we find no evidence that changes in the position of the Intertropical Convergence Zone had a significant influence on the overall moisture availability in central Africa. We conclude that changes in ocean circulation, and hence sea surface temperature patterns, were important in modulating atmospheric moisture transport onto the central African continent. [ABSTRACT FROM AUTHOR]

The youngest and one of the largest saline deposits of Earth history formed in the Mediterranean during the Messinian salinity crisis (MSC; 5.97–5.33 Ma, Late Miocene), when global climate was experiencing a trend of cooling and aridification. However, recent paleoclimate reconstructions indicate strong climate gradients across the Mediterranean Basin and the persistence of humid conditions in the northern Mediterranean during the earliest phase of the MSC. To characterize climatic and hydrologic variability across the onset of the MSC, we studied inorganic geochemical proxies, comprising Si, Ti, and Zr element distributions and organic geochemical proxies, such as sedimentary plant wax contents and their carbon (δ13C n -alk) and hydrogen (δ2Η n -alk) stable isotope compositions in deep-water (>200 m), alternating shale and marl deposits of the Piedmont Basin (Govone section; NW Italy). Our results suggest that deposition was controlled by precession-driven climate fluctuations before and after the onset of the MSC, with shales deposited under moister conditions (lower element/Al ratios and δ2Η n -alk values) and marls when drier conditions prevailed (higher element/Al ratios and δ2Η n -alk values). The observed δ2Η n -alk pattern further suggests changes in the relative contributions of the sources of moisture for precipitation. At precession minima, shales were deposited and moisture was mainly sourced from the North Atlantic, as reflected by lower δ2Η n -alk values. At precession maxima, marls were deposited and higher δ2Η n -alk values point to a – probably western – Mediterranean source of moisture. The decrease of element/Al ratios as well as the coeval increase of plant wax abundances after the onset of the MSC indicate enhanced humidity and increased net precipitation over the northern Mediterranean. These changes coincided with a restriction of the Atlantic-Mediterranean gateways and resulted from an enhanced contribution of deuterium-enriched moisture sourced from seawater evaporation in the Mediterranean, evidenced by an increase of δ2Η n -alk values. • Proxies indicate climate change driven by precession in the Northern Mediterranean. • C 3 vegetation dominated after the onset of the crisis at precession maxima. • Source areas of moisture varied as a function of precession. • Humidity increased after the onset of the Messinian salinity crisis. [ABSTRACT FROM AUTHOR]

Variations in Amazonian hydrology and forest cover have major consequences for the global carbon and hydrological cycles as well as for biodiversity. Yet, the climate and vegetation history of the lowland Amazon basin and its effect on biogeography remain debated due to the scarcity of suitable high-resolution paleoclimate records. Here, we use the isotopic composition ( δ D and δ 13 C) of plant-waxes from a high-resolution marine sediment core collected offshore the Amazon River to reconstruct the climate and vegetation history of the integrated lowland Amazon basin for the period from 50,000 to 12,800 yr before present. Our results show that δ D values from the Last Glacial Maximum were more enriched than those from Marine Isotope Stage (MIS) 3 and the present-day. We interpret this trend to reflect long-term changes in precipitation and atmospheric circulation, with overall drier conditions during the Last Glacial Maximum. Our results thus suggest a dominant glacial forcing of the climate in lowland Amazonia. In addition to previously suggested thermodynamic mechanisms of precipitation change, which are directly related to temperature, we conclude that changes in atmospheric circulation are crucial to explain the temporal evolution of Amazonian rainfall variations, as demonstrated in climate model experiments. Our vegetation reconstruction based on δ 13 C values shows that the Amazon rainforest was affected by intrusions of savannah or more open vegetation types in its northern sector during Heinrich Stadials, while it was resilient to glacial drying. This suggests that biogeographic patterns in tropical South America were affected by Heinrich Stadials in addition to glacial–interglacial climate variability. [ABSTRACT FROM AUTHOR]

Detailed knowledge about tropical South American precipitation patterns during Heinrich (H) and Dansgaard-Oeschger (DO) stadials provides relevant insights into the possible evolution of Amazonian hydroclimate under future climate change. Sediment core GeoB16224-1 (ca. 7°N), raised from a site in the continental slope off French Guiana in western equatorial Atlantic under the influence of the Amazon River discharge, documents the impacts of H and DO stadials on both inorganic (i.e., Fe/Ca record) and organic (i.e., alkenone C 37 concentration and C 37 /C 38 ratio) geochemistry between 41 and 13 ka BP. Our results show millennial-scale covariations of increased Fe/Ca values with decreased C 37 concentration and C 37 /C 38 ratios during H and DO stadials. Comparing our high temporal resolution data with previously published records from ca. 17°N to 4°S, we are able to differentiate the influence of H and DO stadials upon tropical South American precipitation. We find that records under the influence of the South American summer monsoon (e.g., western Amazon) and the northern edge of the Intertropical Convergence Zone (ITCZ) (e.g., northernmost South America) exhibit strong climate shifts during both H and DO stadials, but regions under the influence of the southern edge of the ITCZ (e.g., northeastern Brazil) experience a weaker reaction during DO stadials than during H stadials. [ABSTRACT FROM AUTHOR]

Variations in the sediment input to the Namaqualand mudbelt during the Holocene are assessed using an integrative terrestrial to marine, source to sink approach. Geochemical and Sr and Nd isotopic signatures are used to distinguish fluvial sediment source areas. Relative to the sediments of the Olifants River, craton outcrops in the northern Orange River catchment have a more radiogenic Sr and a more unradiogenic Nd isotopic signature. Furthermore, upper Orange River sediments are rich in heavier elements such as Ti and Fe derived from the chemical weathering of Drakensberg flood basalt. Suspension load signatures change along the Orange River's westward transit as northern catchments contribute physical weathering products from the Fish and Molopo River catchment area. Marine cores offshore of the Olifants (GeoB8323-2) and Orange (GeoB8331-4) River mouths show pulses of increased contribution of Olifants River and upper Orange River input, respectively. These pulses coincide with intervals of increased terrestrial organic matter flux and increased paleo-production at the respective core sites. We attribute this to an increase in fluvial activity and vegetation cover in the adjacent catchments during more humid climate conditions. The contrast in the timing of these wet phases in the catchment areas reflects the bipolar behavior of the South African summer and winter rainfall zones. While rainfall in the Orange River catchment is related to southward shifts in the ICTZ, rainfall in the Olifants catchment is linked to northward shifts in Southern Hemisphere Westerly storm tracks. The later may also have increased southern Benguela upwelling in the past by reducing the shedding of Agulhas eddies into the Atlantic. The high-resolution records of latitudinal shifts in these atmospheric circulation systems correspond to late Holocene centennial–millennial scale climate variability evident in Antarctic ice core records. The mudbelt cores indicate that phases of high summer rainfall zone and low winter rainfall zone humidity (at ca. 2.8 and 1 ka BP) may be synchronous with Antarctic warming events. On the other hand, dry conditions in the summer rainfall zone along with wet conditions in the winter rainfall zone (at ca 3.3, 2 and 0.5 ka BP) may be associated with Antarctic cooling events. [ABSTRACT FROM AUTHOR]

It has long been known that extreme changes in North African hydroclimate occurred during the late Pleistocene yet many discrepancies exist between sites regarding the timing, duration and abruptness of events such as Heinrich Stadial (HS) 1 and the African Humid Period (AHP). The hydroclimate history of the Nile River is of particular interest due to its lengthy human occupation history yet there are presently few continuous archives from the Nile River corridor, and pre-Holocene studies are rare. Here we present new organic and inorganic geochemical records of Nile Basin hydroclimate from an eastern Mediterranean (EM) Sea sediment core spanning the past 28 ka BP. Our multi-proxy records reflect the fluctuating inputs of Blue Nile versus White Nile material to the EM Sea in response to gradual changes in local insolation and also capture abrupt hydroclimate events driven by remote climate forcings, such as HS1. We find strong evidence for extreme aridity within the Nile Basin evolving in two distinct phases during HS1, from 17.5 to 16 ka BP and from 16 to 14.5 ka BP, whereas peak wet conditions during the AHP are observed from 9 to 7 ka BP. We find that zonal movements of the Congo Air Boundary (CAB), and associated shifts in the dominant moisture source (Atlantic versus Indian Ocean moisture) to the Nile Basin, likely contributed to abrupt hydroclimate variability in northern East Africa during HS1 and the AHP as well as to non-linear behavior of hydroclimate proxies. We note that different proxies show variable gradual and abrupt responses to individual hydroclimate events, and thus might have different inherent sensitivities, which may be a factor contributing to the controversy surrounding the abruptness of past events such as the AHP. During the Late Pleistocene the Nile Basin experienced extreme hydroclimate fluctuations, which presumably impacted Paleolithic cultures residing along the Nile corridor. [ABSTRACT FROM AUTHOR]

Mpondoland on the South African east coast is a particularly dynamic region in terms of climate change as it is influenced by both temperate and tropical circulation and climate systems. We present a sediment record that indicates regional climatic change and anthropogenic influence during the last ∼5500 yr. Catchment data allow an understanding of signal transmission from the catchment to the site of the marine core. Plant-wax isotope distributions and elemental composition, as well as palynological, burned phytolith and micro-charcoal data, are used to infer paleoclimatic shifts and reconstruct past human activity. Whereas previous studies have often disregarded early anthropogenic drivers of environmental change, our study provides palynological evidence of human impacts and geochemical evidence of increased erosion starting as early as ∼1500 years ago. Downcore proxy analysis suggests that particularly humid conditions persisted from ∼900 to ∼300 cal yr BP, encompassing both the Medieval Climate Anomaly and the Little Ice Age. We suggest that humidity during the Medieval Climate Anomaly was sourced from a poleward shift of the Southern Hemispheric Westerlies and the South African high-pressure cell, allowing for the southward expansion of the Southern Indian Ocean Convergence Zone. During the Little Ice Age, the equatorward movement of the Southern Hemispheric Westerlies probably brought increased rainfall to areas that are normally beyond the northern limit of the Southern Hemispheric Westerlies. Comparison of our record to available regional archives of centennial-scale late Holocene climate variability in South Africa demonstrates that Mpondoland is located at a transition zone of tropical and sub-tropical climatic influences. • Anthropogenic drivers of environmental change as early as ∼1500 years ago. • A southward expansion of the Southern Indian Ocean Convergence Zone caused a wet Medieval Climate Anomaly in Mpondoland. • A Southern Hemispheric Westerlies equatorward shift brought increased rainfall to Mpondoland during the Little Ice Age. [ABSTRACT FROM AUTHOR]