The fluctuating Aral Sea: A multidisciplinary-based history of the last two thousand years

The Aral Sea (an intracontinental saline lake in western Central Asia) is of great interest because of its rapid shrinkage during the last 50 years, which caused catastrophic environmental and socio-economic consequences for the region and its population. Geoscientists established the existence of similar multiple fast and deep lake level fluctuations in the past; however, a comprehensive picture of these changes has been lacking. In this paper, we summarize published and new geomorphological, sedimentological, paleoenvironmental, geoarcheological, and historical data to reconstruct fluctuations in the Aral during the last two thousand years. Two deep regressions are recognized, in addition to the modern human-induced regression. The regressions occurred at ca. 2.1–1.3 and 1.1–0.35 ka cal BP according to the sedimentary and faunal data, and 2.1–1.45 and 1.0 (0.85)–0.45 ka cal BP according to the archeological and historical data. The Aral Sea lake level dropped to ca. 10 m a.s.l. during the first regression and to ca. 29 m a.s.l. during the second one. Transgressions which separated these periods reached elevations of ca. 52 m a.s.l., and 54 m a.s.l., respectively. According to the current data, the regressions lasted longer than the transgressions, or were of equal duration. Reasons considered for past Aral Sea lake level changes include both natural and human-related causes, as the region features more than 2000 years of agricultural activity.