講演情報
[U11-P10]水月湖の生物源シリカフラックスに記録された最終退氷期の急激な水文気候変動
*村井 円香1、池田 昌之1、中川 毅2、多田 隆治3、堀内 大嗣4、原口 強11,5、北場 育子2、鈴木 克明6、五反田 克也7、山田 圭太郎8、板井 啓明1、Jonathan TYLER9、Alexander FRANCKE9、Vanessa NOWINSKI9、三條 竜平10、溝口 一生10 (1.東京大学大学院理学系研究科、2.立命館大学古気候学研究センター、3.千葉工業大学地球学研究センター、4.海上保安庁、5.東北大学災害科学国際研究所、6.産総研地質調査総合センター、7.千葉商科大学国際教養学部、8.山形大学理学部、9.アデレード大学理学部、10.電力中央研究所、11.株式会社STORY)
キーワード：
年代対比、退氷期、気候変動、東アジアモンスーン、FTIR、湖沼堆積物
Hydroclimatic variability during the last deglaciation (ca. 17-10 ka) was characterized by repeated and pronounced climate fluctuations as the Earth system shifted from glacial to interglacial conditions, including the Bølling–Allerød (B–A) warming period. Lake Suigetsu. located in central Japan, preserves annually laminated (varved) sediments and serves as a reference archive for radiocarbon calibration, enabling high-precision paleoclimate reconstructions at decadal timescales. Pollen-based temperature reconstructions indicate that an abrupt warming at Lake Suigetsu began around 15 ka, approximately 200 years earlier than in Greenland. Immediately following this warming in Suigetsu, light-colored event layers occurred frequently, which have been interpreted as evidence for an increased frequency of extreme flood events—called the “Stormy Two Centuries”, yet precipitation variability during this period remains poorly constrained.
In this study, we conducted centimeter-scale (~10-year resolution) analyses of biogenic silica (BSi) content and flux to evaluate hydrological and climatic changes during the terminal phase of the last deglacial period. BSi contents were quantified using slab-based XRF scanning, FTIR, as well as alkaline digestion, with dissolved Si and Al measured by ICP–AES. To calculate BSi fluxes, dry bulk density was measured continuously at 1-cm intervals. The age model was established based on varve chronology and the IntCal20 radiocarbon calibration curve.
Our results show that the BSi flux did not immediately increase with the local pollen-inferred warming (15.0 ka). This observation suggests that rising local air temperature alone may not have been the primary driver of the silica supply. Instead, a notable rise in BSi occurred at around 14.8 ka, temporally coinciding with the onset of the Bølling-Allerød interstadial in Greenland and the intensification of the Asian Monsoon recorded in Chinese speleothems. The temporal relation supports that the increase in BSi as a potential signal of intensified precipitation and hydrological cycling associated with the northward migration of the ITCZ and Westerlies. These findings imply that the hydrological system in central Japan was sensitive to global atmospheric circulation patterns during the deglaciation.
In this study, we conducted centimeter-scale (~10-year resolution) analyses of biogenic silica (BSi) content and flux to evaluate hydrological and climatic changes during the terminal phase of the last deglacial period. BSi contents were quantified using slab-based XRF scanning, FTIR, as well as alkaline digestion, with dissolved Si and Al measured by ICP–AES. To calculate BSi fluxes, dry bulk density was measured continuously at 1-cm intervals. The age model was established based on varve chronology and the IntCal20 radiocarbon calibration curve.
Our results show that the BSi flux did not immediately increase with the local pollen-inferred warming (15.0 ka). This observation suggests that rising local air temperature alone may not have been the primary driver of the silica supply. Instead, a notable rise in BSi occurred at around 14.8 ka, temporally coinciding with the onset of the Bølling-Allerød interstadial in Greenland and the intensification of the Asian Monsoon recorded in Chinese speleothems. The temporal relation supports that the increase in BSi as a potential signal of intensified precipitation and hydrological cycling associated with the northward migration of the ITCZ and Westerlies. These findings imply that the hydrological system in central Japan was sensitive to global atmospheric circulation patterns during the deglaciation.