[M-IS04] Evolution and variability of the Asian Monsoon and Indo-Pacific climate during the Cenozoic Era

[MIS04-P01] Tropical Western Pacific hydrology during the last 6,000 years based on wildfire charcoal records from Borneo

*Masanobu Yamamoto¹, Takafumi Kikuchi¹, Hiromischi Sakurai¹, Ryoma Hayashi², Osamu Seki³, Takayuki Omori⁴, Abdullah Sulaiman⁵, Hasrizal Shaari⁶, Mohd Zulhilmy Abdhllah⁷, Lulie Melling⁷ (1.Faculty of Environmental Earth Science, Hokkaido University, 2.Lake Biwa Museum, 3.Institute of Low Temperature Science, Hokkaido University, 4.The University Museum, The University of Tokyo, 5.Department of Mineral and Geoscience of Malaysia, 6.Universiti Malaysia Terengganu, 7.Sarawak Tropical Peat Reserach Institute)

Keywords:Charcoal, Paleofire, Borneo, Holocene, Precipitation, Solar forcing

The forcing of multi-centennial climate variability in the Western Pacific Warm Pool (WPWP) region is not fully understood. Here we generated 6-ky long continuous charcoal records from five peatlands in Borneo. Peaks of charcoal abundance every several hundred years were identified at each site, indicating that the peatlands repeatedly experienced aridity and wildfires. Major fire events were identified at ~5.2, 4.7, 4.3, 3.7, 3.1, 2.5, 2.2, 1.6, 1.1, 0.6 and 0.2 ka. Most of these coincided with the maxima of Borneo speleothem δ¹⁸O, and occurred in the high solar activity periods soon after the solar minima. This suggests that the solar minima increased rainfall, leading to fuel accumulation, while the subsequent higher solar activity decreased rainfall, increasing aridity and wildfire frequency. This result challenges the hypothesis that high solar activity intensifies atmospheric convection in the WPWP area.