[P-EM08_2PM1] Space Weather and Space Climate

[PEM08-22] マウンダー極小期の太陽磁場サイクルに対する中部日本・台湾の気候応答

*坂下 渉¹、横山 祐典¹、宮原 ひろ子²、阿瀬 貴博³、米延 仁志⁴、大山 幹成⁵、星野 安治⁶、中塚 武⁷ (1.東京大学 大気海洋研究所 海洋底科学部門、2.武蔵野美術大学造形学部、3.東京工業大学大学院理工学研究科理学研究流動機構、4.鳴門教育大学大学院学校教育研究科、5.東北大学学術資源研究公開センター植物園、6.奈良文化財研究所、7.総合地球環境学研究所)

キーワード：太陽磁場活動, 銀河宇宙線, マウンダー極小期, 年輪同位体

Relationship between solar variations and climate has been long discussed for various time scales. It is difficult to distinguish the impacts of the multiple solar parameters (total solar irradiance (TSI), solar ultraviolet (UV) radiation, and galactic cosmic rays (GCRs)) on climate, because these variations are nearly synchronized. However, GCR fluctuations related to solar magnetic activity have slightly different features compared to the other external forcing factors (TSI, UV). According to previous studies, the cosmic ray fluctuation was particularly unique during the Maunder Minimum (A. D. 1645-1715), when almost no sunspots were observed. Annually measured tree-ring Δ¹⁴C and ice-core ¹⁰Be data have shown that decadal variations of GCRs had been remarkably amplified during the Maunder Minimum. This characteristic amplification may be utilized to shed light on the GCR influence on climate. In this study, we employ tree rings that can reconstruct both annual climate (δ¹⁸O) and cosmic ray fluctuations (Δ¹⁴C) during the Maunder Minimum. By using these proxies, we can directly compare these reconstructions without any dating error. Annually measured tree-ring δ¹⁸O records from central Japan have shown significant wet climate at every remarkable GCRs enhancement. On the other hand, there is no significant climate response in tree-ring δ¹⁸O record from Taiwan. We suggest that these climate responses may be related to a stationary position of the Baiu front. Recent satellite observations have shown that GCRs may cause the increase of low cloud amount at tropical western Pacific region. It can be suggested that cooling of tropical western Pacific region caused by GCR enhancement might have caused the weakening of Pacific high and indirectly brought wet rainy seasons in central Japan.