Alkenone Inferred Holocene Climate Change in Lake Ebeyty, South Western Siberia

Holocene climate in Westerlies Asia, a region sensitive to climate change, has drawn great research interest whereas most studies to date focus on moisture evolution in the core area of the 'westerlies-dominated climate regime' (e.g. Xinjiang and its surrounding areas, Chen et al., 2019). To the north of this core area, the south Western Siberia, where atmospheric blocking (i.e. the Ural blocking) occurs frequently triggering anomalous climate downstream, is less studied. Although a recently reported record from this region indicate a long-term winter warming during the Holocene (Baker et al., 2017), however, Holocene record of warm season climate is still rare, making it unclear as to whether Holocene summer warming prevailed and whether the moisture history is in line with that in central Asia.

Utilizing a sediment core collected from Lake Ebeyty (54.6° N, 71.7° E), south Western Siberia, we reconstruct growing season temperature and moisture change over the past 12 ka by the distribution pattern of long-chain alkenones based on ¹⁴C chronological framework. Alkenone-derived indices U^K'₃₇ and %C_37:4 varied from ~ 0.03 to 0.21 and from ~ 13% to 75% respectively. Our results suggest that the regional climate during the early and mid-Holocene is characterized by a relatively warm period at 12-7.5 ka, followed by a cold period at 7.5-4.5 ka. The warmest climate in our record is captured since 4.5 ka, possibly due to atmospheric blocking, albeit interrupted by serval cold events. Moisture record shows that it was drier during the early and mid-Holocene but wet during the late Holocene, consistent with the moisture evolution pattern in the core area of the Westerlies Asia (Chen et al., 2016). Collectively, the temperature and moisture record indicate a warm-wet/cold-dry climate association in this region, different from that in arid central Asia.