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形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA2230019000, レポート番号: JAXA-SP-22-005E

資料番号: AA2230014000, レポート番号: JAXA-SP-22-004E

形態: 図版あり, Physical characteristics: Original contains illustrations, 資料番号: AA2130016000, レポート番号: JAXA-SP-21-007E

NIOZ - Royal Netherlands Institute for Sea Research, and Utrecht University, Texel, the Netherlands (1); MARUM – Center for Marine Environmental Sciences, Bremen University, Bremen, Germany (2); Department of Earth Sciences, Faculty of Science, Vrije Universiteit Amsterdam, The Netherlands (3); ANU – Australian National University, Research School of Earth Sciences, Canberra, Australia (4); School of Geography, Earth and Environmental Sciences at University of Birmingham, Edgbaston Birmingham, United Kingdom (5); LSCE - Laboratoire des Sciences du Climate et de l’Environnement, Gif-sur-Yvette, France (6); University College London, UCL, dept of Earth Sciences, London, United Kingdom (7); Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, USA (8); JAMSTEC – Japan Agency for Marine Earth Science and Technology, Yokosuka, Japan (9) Australia is the driest inhabited continent on the planet, with its moisture mostly sourced from the tropical monsoon in the north and the southern westerlies in the south. The continent has experienced large climate fluctuations in the geologic past, but long continuous records of palaeo-environmental changes are lacking, particularly prior to ~0.55Ma. Here, we address this paucity by presenting a continuous record of continental aridity and monsoonal activity in northwestern Australia since the Pliocene (5.3 Ma). Our records are based on bulk-chemical XRF-scans and particle-size distributions of the terrigenous fraction, in two cores from the northwestern Australian continental shelf: MD002361 and ODP122-762B. In our records we distinguish between aeolian- and fluvial sediments that were deposited at sea. Support for the distinction between aeolian and fluvial sediment fractions in the two marine sediment cores is found in the bulk-chemical composition of aeolian- and fluvial material in the potential source areas in northern West Australia. Our records show a warm and dry early Pliocene (~5.3 Ma) on the northwestern Australian continent, which experienced a gradual increase in humidity peaking at about 3.8 Ma with higher than present-day rainfall. Between 3.8 and about 2.8 Ma, climate became progressively more arid with more rainfall variability. Coinciding with the onset of the northern hemisphere glaciations and the intensification of the northern-hemisphere monsoon, aridity continued to increase overall from 2.8 Ma until today, with greater variance in precipitation and an increased frequency of large rainfall events. We associate the observed large-scale fluctuations in Australian aridity with variations in Indian Ocean sea-surface temperatures, which largely control the monsoonal precipitation in northwestern Australia.

Supplemental material, HoloceneFL_SI_200619 for Extreme flood events and their frequency variations during the middle to late-Holocene recorded in the sediment of Lake Suigetsu, central Japan by Yoshiaki Suzuki, Ryuji Tada, Kana Nagashima, Takeshi Nakagawa, Katsuya Gotanda, Tsuyoshi Haraguchi and Gordon Schlolaut in The Holocene

A typical case of recognition, classification, and counting of varves. Red lines are clear varves showing moderate (~100) peaks with moderate gradient (5~10) in gray scale. Gray lines are event layers showing high (>100) peaks with high gradient (10~30) in gray scale. Yellow lines are unclear varves (counted as 0~1 year) showing low peaks in gray scale or not horizontally continuous. Figure S2. (A) Sample intervals of SG12LM3 used for Bayesian analysis and (B) estimated age differences between the centers of neighboring sample intervals using Bayesian analysis. Open and close ranges show probabilities of age differences based on varve counting and its coupling with Bayesian analysis, respectively. (PPTX 550 kb)

Millennial-scale variability in the behavior of North Pacific Intermediate Water during the last glacial and deglacial period, and its association with Dansgaard-Oeschger (D-O) cycles and Heinrich events, are examined based on benthic foraminiferal oxygen and carbon isotopes (delta O-18(bf) and delta C-13(bf)) and %CaCO3 using a sediment core recovered from the northeastern slope of the Bering Sea. A suite of positive delta O-18(bf) excursions at intermediate depths of the Bering Sea, which seem at least in part associated with increases in the delta O-18(bf) gradients between the Bering and Okhotsk Seas, suggest the Bering Sea as a proximate source of intermediate water during several severe stadial episodes in the last glacial and deglacial period. Absence of such delta O-18(bf) gradients during periods of high surface productivity in the Bering and Okhotsk Seas, which we correlate to D-O interstadials, suggests a reduction in intermediate water production in the Bering Sea and subsequent introduction of nutrient-rich deep waters from the North Pacific into intermediate depths of the Bering Sea. We argue that a reorganization of atmospheric circulation in the high-latitude North Pacific during severe cold episodes in the last glacial and deglacial period created favorable conditions for brine rejection in the northeastern Bering Sea. The resulting salinity increase in the cold surface waters could have initiated intermediate (and deep) water formation that spread out to the North Pacific.