Radiocarbon ages of insects and plants frozen in the No. 31 Glacier, Suntar-Khayata Range, eastern Siberia

The aim of this study was to estimate the age of glacier ice in the No. 31 Glacier in the Suntar-Khayata Range of eastern Siberia by performing dating of insects thought to be long-legged fly species (Dolichopodidae) as well as plants (species unknown) fragments preserved in the ice. Ice samples containing organisms were collected at depths of 0.4–1.1m at five points from the middle to lowest parts of the glacier in 2013. The age of an insect collected at the lowest point on the glacier was estimated as 2038±32yr B.P. Insects collected at higher points had a modern or near-modern radiocarbon age. The age of plant fragments collected at the uppermost and middle points was 1531±44 and 1288±26yr B.P., respectively, and that of a mixture of plant and insect fragments collected at the lowest point was 9772±42yr B.P. When comparing specimens collected at the same point, the plant fragments were found to be older than the insects. In 2012–2014 observations, some living insects were found on the glacier, and thus the age of the insects appears to correspond to the age of the ice. On the other hand, the plant fragments might have already aged since detachment from the source plants. This study found an approximately 2000-year gap in the age of the ice between the lowest and higher points. Annual mass balance observations from 2012 to 2014 showed that in recent years, the glacier sometimes had no accumulation area. Therefore, the wide gap in the age of ice may be due to a difference in past melting processes between the lowest and higher points on the glacier.