Late Holocene variation of the Raigorodskogo Glacier and climate change in the Pamir–Alai, central Asia

Abstract

During the late Holocene, the Raigorodskogo Glacier in the Pamir–Alai, central Asia expanded before 3215, after 1545, and at 310 cal. years BP, as dated by the 14C-calibrated ages of wood samples from moraine deposits and terrace exposures. The glacier expansions, which were accompanied by increased melt water run-off over the terrace surface, were confined to the proglacial area. The terrace deposits with intercalated buried soil layers provide evidence of two obvious warm periods when the glacier abruptly retreated during the late Holocene, shortly before 1545 cal. years BP and again sometime before ca. 500 cal. years BP. Fallen Juniperus turkestanica, broken by moraine deposits, suggests that the largest glacial expansion during the Little Ice Age occurred 310 cal. years BP. The glacier expansion in the Little Ice Age was on roughly the same scale as that which occurred in the cold period after 1545 cal. years BP. Observational records of the glacier terminus and moraine positions indicate that recent glacier advances occurred in the years 1908–1911, sometime in 1911–1934, and in 1960–1977. These advances were small, while the glacier recessions were larger in the 1900s, with large recessions also sometime in 1911–1934 and in 1977–1998. The glacier recession rate of 27 m/year in 1911–1934 was faster than the rates of 13 m/year in 1977–1990 and 21 m/year in 1990–1998; however, the glacier recession rate has been accelerating recently, particularly after 1990. This recession reflects recent climate warming in inland Asia.