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

Abstract

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 lowstand, 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).

Water Supply and Ancient Society in the Lake Balkhash Basin: Runoff Variability along the Historical Silk Road

“…Extensive floodplain soil development between cal AD 1300-1640 indicates significantly reduced flooding and relatively dry conditions. It also coincides with a major regression of the Aral Sea documented in the late medieval period (Yang et al 2014;Krivonogov et al 2010Krivonogov et al , 2014. The last phase of river aggradation in the Talgar catchment is dated to c. AD 1740 (± 30), and may have continued until the early 20th century.…”

“…Similar to the early-middle Holocene entrenchment phase, it coincided with a Fig. 18.6 Correlation of Holocene Talgar river entrenchment (pink), aggradation (blue) and soil formation (grey) with regional hydroclimatic proxies: a long-term variability of Siberian High (Mayewski et al 2004), b fluctuation of Lake Balkhash and c Aral Sea levels (Krivonogov et al 2010(Krivonogov et al , 2014Endo et al 2012;Sala et al 2015;Chiba et al 2016), d Tian Shan glacial advances (Savoskul and Solomina 1996;Aubekerov and Gorbunov 1999), e soil formation in Central Asia (Sun 2002;Solomina and Alverson 2004;Blättermann et al 2012), and f cultural periodization (Andro. Andronovo community complex of BA).…”

“…With the exception of a sedimentation episode in the Tseganka distributary on the Talgar fan at c. AD 720 (± 260), which coincided with brief high-stands of the Aral Sea cal AD 500-600 and cal AD 850-950 as well as glacier re-advance in the Tian Shan, the period between c. 500 BC and c. AD 1740 was one of reduced geomorphic activity in the Talgar catchment. It coincided with a weakening of the SH between the second half of the 1 st millennium BC and the end of the 14th century AD, as well as with major regressions in the Aral Sea between 150 cal BC-cal AD 600-650 and again between cal AD 850-950 and 1600-1700 (Krivonogov et al 2010(Krivonogov et al , 2014. Extensive floodplain soil development between cal AD 1300-1640 indicates significantly reduced flooding and relatively dry conditions.…”

“…To explore the relationship between river dynamics in the Talgar catchment and climate change in the Holocene, the phases of river aggradation and incision are correlated with: (1) periods of glacier dynamics in the Tian Shan Mountains (Savoskul and Solomina 1996;Sorg et al 2012;Takeuchi et al 2014); (2) water level records in the Aral Sea (Krivonogov et al 2010(Krivonogov et al , 2014 and Lake Balkhash (Endo et al 2012;Sala et al 2015;Chiba et al 2016); (3) regional episodes of soil development (Sun 2002;Solomina and Alverson 2004;Blättermann et al 2012); and (4) strength of the Siberian High Pressure System (SH) (Meeker and Mayewski 2002;Mayewski et al 2004). Although there are quite a wide range of proxy climate records available for the Lake Balkhash Basin, only water levels in the Aral Sea and glacier advances in the Tian Shan span the entire Holocene and have centennial-scale time resolution.…”

The nature of fluctuating lakes in the southern Amu-dar'ya delta

“…Various studies have produced differing patterns of change in water levels. The most recent and the most extensive is that of Krivonogov et al (2010Krivonogov et al ( , 2014) who suggest that it is possible to reliably reconstruct events for the last 2 millennia, including 2 transgressive and 2 regressive phases. They document sea level rises in the 6th-12th and the 16th-20th centuries CE and falls in the 13th-14th centuries CE and, in the most recent regression, since the mid-20th century CE.…”