[M-IS12] 古気候・古海洋変動

[MIS12-P01] 現生花粉酸素同位体比の全国分布から見た環境復元指標としての有用性

*朝日 博史¹、山田 圭太郎²、中川 毅²、志知 幸治³ (1.福井県　里山里海湖研究所、2.立命館大学、3.森林総合研究所)

キーワード：花粉、酸素同位体比、全国分布

Pollen has played marked roles on terrestrial paleoclimate studies. Recent technological development (pollen purifications) promises their potential on chemical analysis over the paleoclimate studies. Despite their rising expectations, there are only limited knowledge on their isotopic signatures, especially in response to general climate signals. Here we present modern distribution of pollen oxygen isotope over Japan, as well as its potential as paleoclimate proxy by their comparison to regional climate indices. Modern pollen oxygen isotopes were selectively measured from sample archives (total 2,400 samples; Year 2016-2023; 60 genus). Prior to isotope measurements, modern pollen-samples were physically and chemically cleaned to make their status close to fossil pollen (sporopollenin). Oxygen isotope measurements were conducted by Elementar GEOVISION® high temperature pyrolysis EA-IRMS in OH-mode. Measured samples (95 samples, cedar, collected in 2021, covering Hokkaido to Kagoshima) exhibit general North-South increasing trend, ranging 21-30 ‰ VSMOW, respectively. Nevertheless, ~2 ‰ VSMOW deviations within close-located samples suggest large influence on their isotope signature by local signals (e.g. Ground water, root length of tree, and tree exposure to sun), demonstrating needs for data “Regional-smoothing” process to ascertain their “General/Macroscopic” trend by minimizing forementioned regional effect. Smoothed data by “near neighbor” technique demonstrates general agreement toward climate variabilities (3 month time window prior to their flowering time in spring) or reported regional oxygen isotopes in rainfall (1972-1993), highlighting their potential usability for paleoclimate reconstruction of Lake Suigetsu.