Drought and dust deposition in the West African Sahel: a 5500-year record from Kajemarum Oasis, northeastern Nigeria

Abstract

A high-resolution, niultiproxy palaeolininological record frorn the Manga Grasslands, northeastern Nigeria, spanning the last 5500 calendar years, reveals the episodic deterioration in Sahelian climate as significant biogeophysical thresholes were crossed.. Desert-dust deposition began to increase -4700 cal. BP. Raintall during the AtLmmer-monsoon season declined permanently after 4100 cal. BP. A further significant change in atmospheric circulation, giving rise to multidecadal to centenniall-scale droughts and enhanced dust deposition.

African hydroclimatic variability during the last 2000 years

“…Compilation of the sedimentological and palynological data (Maley, 1981), anchored in three radiocarbon dates (Maley, 1993) and tuned with available documentary proxy data (Maley, 1989), indicate that the lake stood high from before 1100 CE to 1400 and again in the 17 th century, separated by low to intermediate levels during the 15 th and 16 th centuries. Slightly wetter conditions in this region from 1000 to 1200 CE are also apparent in Sr/Ca and δ 18 O data ( Figure 2) from carbonates in Lake Kajemarum (northeastern Nigeria; Street-Perrott et al, 2000). Additional evidence that relatively humid conditions extended to the easternmost Sahel include the presence of elephants and giraffes near Dongola in Sudan during the 12 th century (present annual rainfall ~20 mm), and extensive pilgrim traffic across the Red Sea during the 13 th century from a port (probably Port Sudan) which was later abandoned for lack of drinking water (Nicholson, 1979).…”

Holocene environmental change in the West African Sahel: sedimentological and mineral‐magnetic analyses of lake sediments from Jikariya Lake, northeastern Nigeria

“…Instead, there is very clear and well-dated stable isotope evidence for a marked drought event from 1200 to 1000 cal. BP (Street-Perrott et al, 2000). It is possible that the desiccation surfaces seen in Bal Lake and Jikariya are local expressions of this drought, but this cannot be verified without better dating.…”

“…1). Some results from these investigations have been published previously (Holmes et al, 1997(Holmes et al, , 1999aSalzmann and Waller, 1998;Street-Perrott et al, 2000;Waller et al, 2007): here, we report sedimentological and mineral magnetic data for a well-dated 690 cm thick sediment sequence from Jikariya Lake and compare them with high-resolution pollen curves (Waller et al, 2007). Despite the existence of well-dated palaeoenvironmental records from two nearby sites investigated under the SAHEL project, together with additional sites further to the east (Kaigama and Kuluwu: Salzmann and Waller, 1998;Fig.…”

Latitudinal Linkages in Late Holocene Moisture‐Balance Variation

“…coeval with "High Medieval" warming in north-temperate Europe (Bradley et al 2003). A pronounced drought episode affecting the western Sahel region of North Africa (Holmes et al 1998) is dated to 1200 -1000 years BP, however, and thus coeval with Central American drought (Street-Perrott et al 2000). Less well constrained chronologically, Lake Chad in the central Sahel also appears to have registered a transgression, rather than lake-level decline, at about 1000 years BP (Maley 1993).…”