Distribution and carbon isotopic composition of long-chain leaf wax n-alkanes from Holocene lake sediments in the Altai Mountains

Abstract

The Altai Mountains are located at the junction of Asia and Europe and pathways linking East Asian climate with the Arctic and North Atlantic. Here, we report a record of n-alkanes from the sediments of Shuanghu Lake in the Altai Mountains. In this forested region, the vegetation is dominated by C3 plants and the long-chain n-alkanes (C29–C31) in the lake sediments are predominantly derived from leaf wax lipids. The compound-specific carbon isotopic values of the long-chain n-alkanes are sensitive to regional moisture. Both the δ13C29–31 value and the Paq index show a decreasing trend since ∼9.0 kyr BP, implying an increase in moisture. This trend is punctuated by abrupt decreases in isotopic values centered at 8.2, 7.4, 5.6, 3.0, 2.0 and 0.2 kyr BP, which may indicate cold and wet events on decadal–centennial timescales. The Holocene hydrological patterns recorded at Shuanghu Lake are different from those from monsoonal Asia and they may reflect a response to decreasing Arctic sea ice cover that provided an enhanced moisture source and promoted increased heavy snowfall in the study region, or an increase in the temperature gradient and strength of the jet stream and extratropical cyclones at mid-latitudes, as proposed previously.