A 3 million year index for North African humidity/aridity and the implication of potential pan-African Humid periods

Grant, Katharine; Rohling, Eelco J.; Westerhold, Thomas; Zabel, Matthias; Heslop, David; Konijnendijk, T.; Lourens, Lucas

doi:10.1016/j.quascirev.2017.07.005

Cited by 127 publications

(184 citation statements)

References 102 publications

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“…Pollen records from Southern Europe also suggest aridity during HS11, with drier, more open vegetation, and large expansion of interglacial vegetation occurring only after 130 ka (Figure g; e.g., Sánchez Goñi et al, ; Tzedakis et al, ; Brauer et al, ; Milner et al, , ; Wulf et al, ). However, two independent Saharan dust proxies, one based on Ti/Al (Konijnendijk et al, ) and the other based on environmental magnetism (IRM 0.9T @AF 120mT ; Larrasoaña, Roberts, Stoner, et al, ), as well as an aridity/humidity index for North Africa (Grant et al, ), imply a reduced influx of Saharan dust to the far eastern Mediterranean during HS11 (Figures h and i). This appears to suggest that HS11 was not as arid as is implied by our African monsoon runoff estimate.…”

Section: Discussionmentioning

confidence: 99%

“…(a) Insolation in mid‐July at 65°N and precession index (Berger & Loutre, ), (b) Atlantic inflow δ 18 O used in inverted model as calculated according to sea level (solid), and with HS11‐associated negative δ 18 O anomaly (dashed; Skinner & Shackleton, ; age constraints: Jiménez‐Amat & Zahn, ; Marino et al, ), 68% and 95% confidence intervals (shaded envelopes), (c) African monsoonal runoff estimate (blue), median (solid line), 68% and 95% confidence intervals (shaded envelopes). African monsoonal runoff estimate when accounting for HS11 with Atlantic freshwater addition (dark blue), median (solid line), 68% and 95% confidence intervals (dotted lines), yellow band indicates modern range of pre‐Awan Nile runoff volume (based on Rohling et al, ), (d) δ 18 O ruber for ODP 967 (green), LC21 (red), KS205 (blue) and ODP 971 (black), median (solid line), 95% confidence intervals (shaded envelopes), (e) percent F. profunda in LC21 (purple; Grelaud et al, ), (f) weight percent organic carbon in LC21 (C org ; gray; Marino et al, ), Isorenieratene concentration in LC21 (orange; Marino et al, ), (g) total tree‐pollen taxa record from Tenaghi Philippon in Greece (dark green; Milner et al, , ; Wulf et al, ), (h) Ti/Al record from ODP967/968 (orange; Konijnendijk et al, ), IRM 0.9T @AF 120mT record from ODP 967 (dark red; Larrasoaña, Roberts, Rohling et al, ), (i) wet‐dry index from ODP 967 (Grant et al, ). S5 interval (gray‐shaded band), timing of HS11 (blue shaded band; Marino et al, ).…”

Section: Calculation Of African Monsoon Runoffmentioning

confidence: 99%

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Quantification of African Monsoon Runoff During Last Interglacial Sapropel S5

Amies

Rohling

Grant

et al. 2019

Paleoceanog and Paleoclimatol

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Organic‐rich sapropel layers punctuate the eastern Mediterranean sedimentary sequence, recording deep‐sea anoxic events. The timing of sapropel deposition coincides with precession minima, which are associated with the northward migration of the monsoon rain belt over North Africa. The resultant increase in monsoon precipitation over the Sahara caused an increase in low‐δ18O freshwater runoff into eastern Mediterranean surface waters, which is reflected by negative δ18O anomalies in the records of planktic foraminiferal calcite. However, despite extensive research on sapropels, the magnitude of monsoon intensification and freshwater runoff, along with its influence on δ18O, remains elusive. Here, we present a quantification of African monsoon freshwater runoff into the eastern Mediterranean for the period of deposition of last interglacial sapropel S5 (~128.3–121.5 ka). Our method uses a box model of the Mediterranean Sea, which represents different water masses, and has been calibrated using δ18O from planktic foraminiferal species of different depth and seasonal habitats. The model was constrained with existing records of sea level and sea surface temperature then inverted to deconvolve the δ18O signal of the surface‐dwelling foraminiferal species Globigerinoides ruber (w) and calculate the freshwater runoff volume. Our calculated African monsoon runoff suggests large increases in freshwater discharge to the eastern Mediterranean (up to ~8.8 times the modern pre‐Aswan Nile discharge). Rapid onset of S5 deposition following the estimated increase in runoff strongly suggests a preconditioning of the eastern Mediterranean for sapropel deposition. Our study also provides insight into the stratification and warming of eastern Mediterranean surface waters during the S5 interval.

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Section: Discussionmentioning

confidence: 99%

Section: Calculation Of African Monsoon Runoffmentioning

confidence: 99%

Quantification of African Monsoon Runoff During Last Interglacial Sapropel S5

Amies

Rohling

Grant

et al. 2019

Paleoceanog and Paleoclimatol

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“…First and foremost, it challenges the existence of a persistent drier period between 77 and 11 ka bp in northwest Africa as proposed in some previous studies (e.g. Grant et al., ; Tjallingii et al., ). Instead, the sedimentary succession of the Agadir‐Tissint Feija clearly evidences that wetter conditions than today prevailed all along this time interval, perhaps enhanced during high insolation maxima.…”

Section: Interpretation and Discussionmentioning

confidence: 83%

“…Extrapolated timing of sequences S2 and S3 is represented based on the relation between S1 and the insolation curve (Laskar et al., ) suggesting that humid periods in the Agadir‐Tissint Feija are correlated with high insolation periods. Regional humidity indexes (Grant et al., ; Tjallingii et al., ) reveal that humid periods recorded by S1 are not anticipated by these indexes. Timing of moraines development in the High Atlas Mountain (from Hughes et al., ) indicates a regional cooling probably related with the change in material production in the catchment and increased sediment supply in the depocentre during the LGM…”

Section: Interpretation and Discussionmentioning

confidence: 99%

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Fluvio‐lacustrine sedimentation in the Agadir‐Tissint Feija (Anti‐Atlas, Morocco): A promising palaeoclimate archive for the last glacial cycle in northwest Africa

Nutz

Kwiecien

Breitenbach

et al. 2019

The Depositional Record

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Mountainous depocentres are often the single available archives in intracontinental areas. As such, the investigation of their sedimentary dynamics is the only way to reconstruct palaeoenvironmental evolution in these peculiar regions. Here, the basin‐scale sedimentary dynamics of the Agadir‐Tissint Feija (i.e. feija is the local name for lowlands) are discussed together with new palaeoenvironmental information on the late Quaternary in the north‐western Sahara margin. The succession consists of up to ca 40 m thick fluvio‐lacustrine deposits subdivided into three depositional sequences (S1–S3) that were deposited between ca 75 ka and ca 10 ka. S1 and S2 reflect the evolution of a palaeolake intercalated by carbonate‐rich palustrine to alluvial plain environments, while S3 shows the transition to an entirely clastic alluvial plain environment. The three sequences are genetically associated with three pulses of tufa buildups at the outlet of the depocentre. Each pulse of tufa buildup is attributed to wet conditions, while each interruption is associated with drier conditions. The wet–dry alternation at the origin of S1 fits with summer insolation fluctuation suggesting that precession parameters may have paced long‐term climate variability in the area. Superimposed on wet–dry cycles, submillennial‐scale (750–900 year) shorter‐term lake fluctuations are identified in S1 and S2; their origins may be related to North Atlantic Oscillation mechanisms. Furthermore, the sudden increase in clastic sediment supply in S3 evidences a change in sediment production in the catchment area attributed to lower temperatures established during the last glacial period. Finally, this newly identified continental archive is unique at the northern Sahara margin; it enables reconstructions of the local and regional hydrological conditions during the last glacial cycle. Even if a more systematic investigation of palaeoclimate forcing is still necessary, the Agadir‐Tissint Feija will potentially bring important information to understand past and anticipate future regional climate change.

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Environmental Controls on Human Dispersal and Adaptation

Parker¹,

Underdown²

2023

Handbook of Archaeological Sciences

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A 3 million year index for North African humidity/aridity and the implication of potential pan-African Humid periods

Cited by 127 publications

References 102 publications

Quantification of African Monsoon Runoff During Last Interglacial Sapropel S5

Quantification of African Monsoon Runoff During Last Interglacial Sapropel S5

Fluvio‐lacustrine sedimentation in the Agadir‐Tissint Feija (Anti‐Atlas, Morocco): A promising palaeoclimate archive for the last glacial cycle in northwest Africa

Environmental Controls on Human Dispersal and Adaptation

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