Environmental Changes of the Aral Sea (Central Asia) in the Holocene: Major Trends

Abstract

Changes of the Aral Sea level have been observed in 3 sediment boreholes, 2 outcrops, and associated archaeological sites. The obtained results are supported by 25 radiocarbon dates. Major trends of lake-level changes have been reconstructed in some detail for the last 2000 yr, and additional data provide an outline of fluctuations throughout the Holocene. Several distinct changes are shown to precede the modern, human-induced regression of the Aral Sea. These include: 1) the latest maximum in the 16th–20th centuries AD (53 m asl); 2) a Medieval “Kerderi” minimum of the 12th–15th centuries AD (29 m asl); 3) the early Medieval maximum of the 4th–11th centuries AD (52 m asl); and 4) a near BC/AD low-stand, whose level is not well established. Since then, events are only inferred from sparse data. The studied cores contain several sandy layers representing the lowering of the lake level within the Holocene, including the buried shore-bar of ∼4500 cal BP (38 m asl), and shallow-water sediments of ∼5600 cal BP (44 m asl), 7200 cal BP (28 m asl), and 8000 cal BP (26.5 m asl).