Hydroclimate variability in the Nile River Basin during the past 28,000 years

doi:10.1016/j.epsl.2015.12.014

Earth and Planetary Science Letters

Volume 438, 15 March 2016, Pages 47-56

https://doi.org/10.1016/j.epsl.2015.12.014 Get rights and content

Highlights

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Nile River basin hydroclimate is explored using a multi-proxy approach.
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Abrupt and gradual responses of individual hydroclimate proxies are noted.
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Zonal migrations of the Congo Air Boundary contributed hydroclimate variability in North Africa.
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Heinrich Stadial 1 evolved in two phases in the Nile Basin.

Abstract

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.

Introduction

The paleoclimate history of the Nile River valley in East Africa is of interest due to its rich history of human occupation (Vermeersch and Van Neer, 2015). Relationships between climate and the distribution of settlements on the Nile River corridor have long been recognized and it is hypothesized that extreme changes in African hydroclimate helped shape the growth and led to the decline of numerous complex societies (Kuper and Kröpelin, 2006). One of the most dramatic changes in North African hydroclimate, the so-called African Humid Period (AHP) (de Menocal et al., 2000), occurred during the early Holocene when increased rainfall allowed vegetation, lakes and human populations to occupy a “green Sahara”, a region that today is a hyperarid desert (Kuper and Kröpelin, 2006). Variability in Nile River flow also played an important role in shaping Egypt's civilizations with the collapse of the Old Kingdom at 4160 yr before present, attributed to a 30 yr absence of annual Nile flooding (Stanley et al., 2003). Although lacking direct evidence, it is hypothesized that HS1, which is recognized as an extreme and widespread drought in North Africa, also had a major impact on Paleolithic cultures (Stager et al., 2011).

Previous investigations of North African hydroclimate since the Last Glacial Maximum (LGM) have documented abrupt and extreme hydrological fluctuations as well as considerable temporal and spatial heterogeneity. The timing and duration of the AHP varies with latitude (e.g. Kuper and Kröpelin, 2006) with sites in the north experiencing a shorter humid phase and earlier termination than sites in the south (Shanahan et al., 2015), following changes in northern hemisphere summer insolation. However, whether the transitions leading into and out of the AHP were abrupt, gradual or stepwise (Fig. 1) remains a highly debated issue (e.g. Kuper and Kröpelin, 2006, Costa et al., 2014, de Menocal et al., 2000, Kuhlmann et al., 2004, Schefuß et al., 2005; Tierney and de Menocal, 2013; Tierney et al., 2008, McGee et al., 2013, Junginger et al., 2014, Weldeab et al., 2014, Marshall et al., 2011, Kutzbach and Street-Perrott, 1985, Claussen et al., 1999). In East Africa, the role of non-linear biogeophysical climate feedbacks is also debated with recent studies concluding that non-linear biogeophysical climate feedbacks between precipitation and vegetation are absent (Weldeab et al., 2014), that a non-linear convection feedback associated with Indian Ocean SST could be an important contributor to rainfall variability (Tierney and de Menocal, 2013), or that a non-linear change in vegetation and sediment erosion occurred in the Early Holocene without a significant decrease in precipitation (Blanchet et al., 2014).

Presently, a gap in our understanding of North African hydroclimate stems from a lack of continuous archives in the vast Nile River corridor (Bard, 2013), which spans 35 degrees of latitude (4°S to 31°N) over its ca. 6670 km course and has a catchment of nearly 3 million km². Here, we investigate the spatially integrated temperature and hydroclimate history of the Nile River Basin by examining the geochemistry of a sediment core collected from the Eastern Mediterranean (EM) Sea that receives sediment from the Nile River. We measured multiple organic and inorganic geochemical parameters on the same samples to provide a robust assessment of past hydroclimate variability and to examine shifts in the dominant sources of material transported by the Nile River to the EM Sea. We focus the discussion on two extreme and contrasting hydroclimate events: Heinrich Stadial (HS) 1, an arid interval driven by an abrupt external forcing, and the AHP, a wet period driven by gradual changes in insolation. We note that the term abrupt is used qualitatively in many paleoclimate studies; for the purpose of this study we consider an event as abrupt if its onset or termination occurs in 1000 yr or less.

Section snippets

Study location

Sediment core GeoB7702-3 was collected from the continental slope offshore Israel (31°39.1′N, 34°04.4′E, 562 m water depth) during R/V Meteor cruise M52/2 in 2002 (Fig. 2) (Pätzold et al., 2003). The chronology of this 592 cm long core, which spans the past 28,000 yr before present (hereafter 28 ka BP), is based on 15 AMS ¹⁴C dates on foraminifera and was previously published along with alkenone and TEX₈₆ sea surface temperature (SST) estimates (Castañeda et al., 2010). The surface currents

Organic geochemical analyses

Core GeoB7702-3 was sampled at 5 cm intervals (average time step of 209 yr) for organic geochemical analyses using the methods detailed by Castañeda et al. (2010). Freeze dried sediment samples were extracted with 9:1 dichloromethane (DCM)/methanol (v/v) using an Accelerated Solvent Extractor (ASE 200). Alumina oxide column chromatography was used to separate apolar, ketone and polar fractions with solvent mixtures of 9:1 hexane/DCM (v/v), 1:1 hexane/DCM (v/v), and 1:1 DCM/methanol (v/v),

Sources of material to the coring site

Due to its large size, the presence of multiple vegetation zones and contrasting environmental conditions within the Nile Basin, a first step to interpreting the GeoB7702-3 proxy records was to determine the main sources of terrestrial material to the core site. The Nile River is comprised of two major tributaries, the White Nile and the Blue/Atbara Nile, which drain contrasting geologic terranes and climate zones (Krom et al., 2002). The Blue Nile, sourced at Lake Tana, and the Atbara, drain

Conclusions

Our multi-proxy study demonstrates that dramatic hydroclimate variability occurred in Nile Basin during the past 28,000 yr. Overall, our new Nile Basin records support other North African hydroclimate records while providing information regarding shifts in the dominant sources of material delivered to the EM Sea via the Blue Nile and the White Nile. While δD_wax is often interpreted to reflect precipitation amount in the African tropics, our data suggest that shifting moisture sources, related

Acknowledgments

We thank Marianne Baas, Ellen Hopmans, Jort Ossebaar and Michiel Kienhuis for analytical assistance. We thank two anonymous reviewers for thoughtful comments that improved the manuscript. Research funding was provided by NEBROC-2. Samples from GeoB7702-3 were supplied through the assistance of the University of Bremen, Geosciences Department and MARUM. This work was supported by the DFG-Research Center/Excellence Cluster “The Ocean in the Earth System”.

References (68)

W.L. Balsam et al.
Magnetic susceptibility as a proxy for rainfall: worldwide data from tropical and temperate climate
Quat. Sci. Rev.
(2011)
M. Ben Israel et al.
Provenance of the various grain-size fractions in the Negev loess and potential changes in major dust sources to the Eastern Mediterranean
Quat. Res.
(2015)
M.A. Berke et al.
Molecular records of climate variability and vegetation response since the Late Pleistocene in the Lake Victoria basin, East Africa
Quat. Sci. Rev.
(2012)
C.L. Blanchet et al.
High- and low-latitude forcing of the Nile River regime during the Holocene inferred from laminated sediments of the Nile deep-sea fan
Earth Planet. Sci. Lett.
(2013)
I. Bouimetarhan et al.
Sahel megadrought during Heinrich Stadial 1: evidence for a three-phase evolution of the low- and midlevel West African wind system
Quat. Sci. Rev.
(2012)
M. Box et al.
Response of the Nile and its catchment to millennial-scale climatic change since the LGM from Sr isotopes and major elements of East Mediterranean sediments
Quat. Sci. Rev.
(2011)
W. Broecker et al.
How did the hydrologic cycle respond to the two-phase mystery interval?
Quat. Sci. Rev.
(2012)
K. Costa et al.
Isotopic reconstruction of the African Humid Period and Congo Air Boundary migration at Lake Tana, Ethiopia
Quat. Sci. Rev.
(2014)
P. de Menocal et al.
Abrupt onset and termination of the African Humid Period: rapid climate responses to gradual insolation forcing
Quat. Sci. Rev.
(2000)
C. Deniel et al.
Single–stage method for the simultaneous isolation of lead and strontium from silicate samples for isotopic measurements
Anal. Chim. Acta
(2001)

A. Junginger et al.

The effects of solar irradiation changes on the migration of the Congo Air Boundary and water levels of paleo-Lake Suguta, Northern Kenya Rift, during the African Humid Period (15–5 ka BP)

Palaeogeogr. Palaeoclimatol. Palaeoecol.

(2014)

J.-H. Kim et al.

Influence of deepwater derived isoprenoid tetraether lipids on the paleothermometer in the Mediterranean Sea

Geochim. Cosmochim. Acta

(2015)

H.F. Lamb et al.

Late Pleistocene desiccation of Lake Tana, source of the Blue Nile

Quat. Sci. Rev.

(2007)

B. Maher et al.

Statistical models for use of palaeosol magnetic properties as proxies of palaeorainfall

Glob. Planet. Change

(2013)

M.H. Marshall et al.

Late Pleistocene and Holocene drought events at Lake Tana, the source of the Blue Nile

Glob. Planet. Change

(2011)

D. McGee et al.

The magnitude, timing and abruptness of changes in North African dust deposition over the last 20,000 yr

Earth Planet. Sci. Lett.

(2013)

D.R. Muhs et al.

Origin of the Sinai–Negev erg, Egypt and Israel: mineralogical and geochemical evidence for the importance of the Nile and sea level history

Quat. Sci. Rev.

(2013)

F. Naughton et al.

Wet to dry climatic trend in north-western Iberia within Heinrich events

Earth Planet. Sci. Lett.

(2009)

F. Peterse et al.

Revised calibration of the MBT–CBT paleotemperature proxy based on branched tetraether membrane lipids in surface soils

Geochim. Cosmochim. Acta

(2012)

C. Pin et al.

Concomitant separation of strontium and samarium–neodymium for isotopic analysis in silicate samples, based on specific extraction chromatography

Anal. Chim. Acta

(1994)

M. Revel et al.

100,000 years of African monsoon variability recorded in sediments of the Nile margin

Quat. Sci. Rev.

(2010)

J. Stanford et al.

A new concept for the paleoceanographic evolution of Heinrich event 1 in the North Atlantic

Quat. Sci. Rev.

(2011)

J.E. Tierney et al.

A Bayesian, spatially-varying calibration model for the TEX₈₆ proxy

Geochim. Cosmochim. Acta

(2014)

J.E. Tierney et al.

Late Quaternary behavior of the East African monsoon and the importance of the Congo Air Boundary

Quat. Sci. Rev.

(2011)

J.E. Tierney et al.

Model, proxy and isotopic perspectives on the East African Humid Period

Earth Planet. Sci. Lett.

(2011)

J.W.H. Weijers et al.

Environmental controls on bacterial tetraether membrane lipid distribution in soils

Geochim. Cosmochim. Acta

(2007)

S. Weldeab et al.

Provenance of lithogenic surface sediments and pathways of riverine suspended matter in the Eastern Mediterranean Sea: evidence from ¹⁴³Nd/¹⁴⁴Nd and ⁸⁷Sr/⁸⁶Sr ratios

Chem. Geol.

(2002)

M. Williams et al.

Abrupt return of the summer monsoon 15,000 years ago: new supporting evidence from the lower White Nile valley and Lake Albert

Quat. Sci. Rev.

(2006)

R. Amit et al.

The role of the Nile in initiating a massive dust influx to the Negev late in the middle Pleistocene

Geol. Soc. Am. Bull.

(2011)

H.W. Arz et al.

Influence of Northern Hemisphere climate and global sea level rise on the restricted Red Sea marine environment during termination I

Paleoceanography

(2003)

E. Bard

Out of the African Humid Period

Science

(2013)

E. Bard et al.

Hydrological impact of Heinrich events in the subtropical northeast Atlantic

Science

(2000)

C.L. Blanchet et al.

Asynchronous changes in vegetation, runoff and erosion in the Nile River Watershed during the Holocene

PLoS ONE

(2014)

P. Camberlin

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Hydroclimate variability in the Nile River Basin during the past 28,000 years

Highlights

Abstract

Introduction

Section snippets

Study location

Organic geochemical analyses

Sources of material to the coring site

Conclusions

Acknowledgments

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