[M-IS06] Evolution and variability of the Tropical Monsoon and Indo-Pacific climate during the Cenozoic Era

[MIS06-07] Changes in the Tsushima Warm Current System in the Japan Sea Throughout the Holocene

*Kenji Matsuzaki¹, Takuya Itaki², Takuya Sagawa³, Yoshiaki Suzuki², Tomohisa Irino⁴, Ken Ikehara² (1.Atmosphere and Ocean Research Institute, The university of Tokyo, 2.AIST, Geological Survey of Japan, Higashi 1-1-1, Tsukuba Central 7, Ibaraki 305-8567, Japan, 3.Institute of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa, 920-1192, Japan, 4.Graduate School of Environmentral Science, Hokkaido University, N10W5 Sapporo Hokkaido 060-0810, Japan)

Keywords:Japan Sea, Holocene, Tsushima Warm Current, Arctic Oscillation

The Japan Sea, connected to adjacent seas through four shallow straits (Tsushima, Tsugaru, Soya, and Mamiya), is characterized by limited water exchange restricted to surface waters, leading to the formation of unique Japan Sea Proper Water. The Tsushima Warm Current (TWC), originating from the East China Sea, is the primary current system transporting heat and nutrients in this semi-enclosed basin. During the Holocene (last 11,700 years), global climate experienced distinct phases: Early Holocene warming (11,700-8,200 BP), Mid-Holocene maximum warmth (8,200-4,200 BP), and Late Holocene cooling (4,200 BP-present). The Arctic Oscillation (AO), a significant climate pattern affecting the Northern Hemisphere, influences winter weather patterns and potentially impacts Japan Sea oceanography and TWC dynamics. Previous studies have demonstrated strong relationships between radiolarian species distribution and water mass properties, particularly nutrients and sea surface temperature (SST). This study aims to reconstruct TWC evolution throughout the Holocene and investigate possible connections with AO phases through analysis of radiolarian assemblages from 7 sediment cores collected along a south-north transect in the Japan Sea by the Geological Survey of Japan (Exp. DGC6; GH93-82; GH95-1202; GH96-1217; GH772-P103; GH872-308) and JAMSTEC (Exp. KR15-10). We will reconstruct paleo-SSTs based on radiolarian assemblages and compare them with TWC-related species fluxes and nutrient-indicator species to evaluate TWC variability during different Holocene climate phases and AO conditions.