Holocene climatic, hydrological and environmental oscillations in the tropics with special reference to Africa

Abstract

The tropics have experienced large and sometimes abrupt fluctuations in the water balance since the beginning of the Holocene period. Water levels were generally high in the equatorial region and northern hemisphere at the beginning of the Holocene, a trend that was asynchronous with many southern hemisphere records. Apart from a desiccation event in many African lakes between 8, 000 and 7, 500 yr BP (Before Present), water levels continued to be high until c.5, 000 yr BP. Southern hemisphere sites experienced intermediate to high lake levels at c.6, 000 yr BP. The tropical lakes experienced a drying phase between 5, 000 and 3, 000 yr BP, and these arid conditions have continued to the present day. Tropical glaciers have, on the other hand, been gradually receding during the Holocene period, but there have been several minor advances. After about 8, 000 yr BP, glacial events show much less spatial consistency. The environmental response has been less marked, but the major trend is from wet/moist vegetation in the early Holocene to drier vegetation from the middle Holocene to the present. The climatic, hydrological and environmental oscillations of the low-latitude regions during the Holocene are linked to changes in earth surface temperatures, sea surface temperatures (SSTs), ocean and atmospheric circulation patterns, regional topography, land surface albedo, etc.