研究等業績 - 原著論文 - Stephen P. Obrochta

MERIDIONAL MIGRATIONS of the INTERTROPICAL CONVERGENCE ZONE during the LAST DEGLACIATION in the TIMOR SEA DETECTED by EXTENSIVE RADIOCARBON DATING

Nemoto K.

Radiocarbon ( Radiocarbon )  66 ( 6 ) 1958 - 1967   2024年12月  [査読有り]

研究論文（学術雑誌）  

At the Intertropical Convergence Zone (ITCZ), the northern and southern Tradewinds converge, and this region is characterized by low atmospheric pressure and high precipitation. The climate in the Timor Sea is characterized by seasonal precipitation changes driven by meridional migrations of the ITCZ and the monsoonal front. The ITCZ shifts in response to changes in the thermal balance between the northern and southern hemispheres. Thus, reconstruction of paleo-precipitation in the Timor Sea is expected to reveal past changes in both regional and global climate, the latter through inference of the ITCZ position. To reconstruct paleo-precipitation in the Timor Sea, we performed extensive radiocarbon analysis on both planktonic foraminifera and total organic carbon (TOC), which is derived from terrestrial and marine sources. Increased precipitation enhances the fraction of relatively old, terrestrial carbon to the core site, which in turn increases the difference between the ages of TOC and planktonic foraminifera. Variations in radiocarbon ages reveal that during northern hemisphere cooling intervals such as Heinrich Stadial 1 and the Younger Dryas, the ITCZ was in a southern position, thus increasing precipitation in the Timor Sea. However, the Timor Sea was dryer during the Bølling-Allerød warming as the ITCZ shifted northward.

DOI

A Lake at the Mt. Fuji (Lake Motosu) Recording Prolonged Negative Arctic Oscillation as Reduction of Aeolian Dust Due To Westerly Pathways During the Holocene

Nemoto K.

Paleoceanography and Paleoclimatology ( Paleoceanography and Paleoclimatology )  39 ( 9 )   2024年09月

研究論文（学術雑誌）  

Abstract

East Asia is a major source of dust accounting for 20% of the global dust emission. Work on reconstructing past changes in dust transport in East Asia is complicated by difficulties in distinguishing local sedimentation from aerial material and lack of suitable material for age determination. Here, we address these issues and present a new dust proxy record from Lake Motosu, located on the Pacific side of Japan. The record is anchored by a high‐quality tephra and radiocarbon chronology. Because Lake Motosu is situated in a quartz‐free basaltic volcanic province, all quartz deposited in the lake is likely to be aerially sourced, and variations in quartz content should reflect past changes in dust transport. Our new record detects a low dust deposition event from 3.0 to 2.0 ka. This event corresponds to elevated sea surface temperature in the Sea of Japan and climate conditions similar to a negative phase of the Arctic Oscillation, indicating an association with the weakened Westerlies and with less frequent dust storms in the source region. The increase in spatial resolution of past dust transport reconstructions will further improve our understanding of the mechanism related to dust emission from East Asia.

DOI

Development of an automated extraction and radiocarbon dating method for fossil pollen deposited in lake Motosu, Japan

Ota K.

Quaternary Science Advances ( Quaternary Science Advances )  15   100207 - 100207   2024年09月  [査読有り]

研究論文（学術雑誌）  

DOI

An initial attempt to date Pleistocene marine terraces in the south coast of Japan using in situ cosmogenic ¹⁰Be and ²⁶Al

Yokoyama Y.

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms ( Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms )  535   255 - 260   2023年02月

研究論文（学術雑誌）  

DOI

Occurrence mode of Holocene tsunami overwash controlled by the geomorphic development along the eastern Nankai Trough, central Japan

Fujiwara O.

Quaternary Science Reviews ( Quaternary Science Reviews )  292   107639 - 107639   2022年09月  [査読有り]

研究論文（学術雑誌）  

DOI