Palaeoenvironmental change and glacier fluctuations in the high Tian Shan Mountains during the last millennium based on sediments from Lake Ala Kol, Kyrgyzstan

Abstract

A suite of limnological proxies measured in clastic sediments of the glacier-fed Lake Ala Kol (NE Kyrgyzstan) document palaeoenvironmental change and glacier fluctuations in the central Tian Shan over the last millennium. Rock magnetic and geochemical data provide supporting evidence for three glacier expansion episodes occurring in 1200–1400 CE, 1500–1850 CE and 1900–1950 CE and glacier retreat periods during 1000–1200 CE and the intervening periods. The maximal glacier extent, as inferred from high κLF, Si/inc + coh, Ca/inc + coh and low ARM30/ARM, is recorded between 1500 and 1850 CE and corresponds to cold and wet conditions during the Little Ice Age in the high central Tian Shan. Periods of glacier waxing and waning recorded at Lake Ala Kol present a close correspondence to ice accumulation rate in the northern Tibetan Plateau, suggesting that precipitation changes are the main driver of glacier fluctuations in central Tian Shan during the last millennium, although temperature may have exerted a more complex influence on centennial timescales.