Abstract
Quantitative paleotemperature reconstruction is a challenging and important issue in paleoenvironmental studies, for which carbonate clumped isotope (Δ47) thermometry is a promising approach. Here we analyzed Δ47 values from 66 layers of OT02 stalagmite from Ohtaki Cave in central Japan, covering two separate time intervals (2.6–8.8 and 34.8–63.5 ka) to reconstruct terrestrial temperature and meteoric δ18O records. The average Δ47 temperatures of the Holocene interval and the latest Pleistonece interval were 16.3 °C ± 5.6 °C and 9.7 °C ± 4.6 °C, respectively. The Δ47 thermometry also revealed that the cold intervals (5 °C–10 °C) correspond to the Heinrich stadials HSs4–6, and the warm interval (up to 19.9 °C ± 6.0 °C) in middle Holocene (approximately 6–5 ka) accompanied by the Hypsithermal climate optimum. We also reconstructed past meteoric δ18O by subtracting the temperature effect from stalagmite δ18O. Average meteoric δ18O was −8.2‰ ± 1.0‰ vs. VSMOW in the Holocene interval and − 8.8‰ ± 0.8‰ in the latest Pleistocene interval. Over centennial timescales, meteoric δ18O was more negative during colder periods, such as Heinrich stadials and a cooling event around 7 ka, and less negative in warmer periods, such as Hypsithermal warming. A temperature dependency of total 18O fractionation from sea water to precipitation is a likely reason for the negative correlation between temperature and meteoric δ18O. Additionally, East Asian summer monsoon (EASM) brought larger rainfall of less negative δ18O during the warm periods, whereas larger snow/rainfall of more negative δ18O brought from East Asian winter monsoon (EAWM) in colder periods. The relative influences from EASM and EAWM were changing in a centennial timescale. δ18O of OT02 had reflected changes in terrestrial temperature and meteoric δ18O, which are both strongly related to EASM and EAWM.
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