RECORD OF HOLOCENE PALEOCLIMATIC EVENTS IN OXYGEN ISOTOPE VARIATIONS (δ18Оtotal, δ18Оcel) IN PEATBOG OF CENTRAL SIKHOTE-ALIN
N.G. Razjigaeva1,2, L.A. Ganzey1, G.V. Simonova3, P.S. Belyanin1, V.V. Chakov4, M.A. Klimin4, E.N. Zakharchenko4, Kh.A. Arslanov5, F.E. Maksimov5, V.A. Grigoriev5
1Pacific Geographical Institute FEB RAS, Vladivostok, Russia
2Institute of Geography RAS, Moscow, Russia
3Institute of Monitoring of Climatic and Ecological Systems SB RAS, Tomsk, Russia
4Institute of Water and Ecological Problems FEB RAS, Khabarovsk, Russia
5St. Petersburg State University, St. Petersburg, Russia
Keywords: oxygen stable isotopes 18О/16О, ɑ-cellulose, climatic changes, monsoon circulation, Siberian High, winter cyclogenesis, Okhotsk High, Southern Far East
Abstract
The composition of stable oxygen isotopes 18O/16O was determined in peat samples and ɑ-cellulose isolated from a peat bog in the Bolotisty Stream valley, Khor River basin, Central Sikhote-Alin. Their vertical variability was traced in peat section that began to accumulate ~10530 cal. yr BP. The δ18Ocel values range from 12.8 to 19.8‰, and δ18Ototal – from 13.6 to 23‰. An increase in δ18Ototal values was recorded up the peat bog section. Significant changes in the vertical distribution of δ18Ocel values, which are indirect indicators of hydroclimatic changes, were revealed. The influence of the botanical composition of peat-forming plants on the oxygen isotope composition was analyzed. Based on the minimum values of δ18Ocel, 19 short-term cold events were identified, their ages were determined, and compared with regional and global events. As a rule, cold events coincided with solar activity minima and were accompanied by a decrease in moisture. The activation of the Siberian High and Okhotsk High, which intensified the effect of cooling, played a major role in the atmospheric circulation during these periods. In some periods, heavy snowfalls associated with an increased frequency of southern cyclones may have influenced the decrease in δ18Ocel
values. More detailed data were obtained for the middle Holocene, when the peat accumulation rate was highest. It was established that the Holocene Optimum was heterogeneous and had a complex structure. The oxygen isotope data recorded a reorganization of the climate from the Holocene Optimum to cooler conditions 5670–5410 cal. yr BP. In the late Holocene, a cold event of 4460–4220 cal. yr BP and a cooling event culminating at 1480 cal. yr BP, comparable to the global event of 1600–1400 cal. yr. BP, were clearly manifested. In the last millennium, cooling events coincided with the Oort, Maunder, and possibly Dalton minima of solar activity.
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