East Asian Monsoon History and Paleoceanography of the Japan Sea Over the Last 460,000 Years

Abstract

The Japan Sea is directly influenced by the Asian monsoon, a system that transports moisture and heat across southeast Asia during the boreal summer, and is a major driver of the Earth's ocean-atmospheric circulation. Foraminiferal and facies analyses of a 460-kyr record from Integrated Ocean Drilling Program Expedition 346 Site U1427 in the Japan Sea reveal a record of nutrient flux and oxygenation that varied due to sea level and East Asian monsoon intensity. The East Asian summer monsoon (EASM) was most intense during marine isotope stage (MIS) 5e, MIS 7e, MIS 9e, and MIS 11c when the Tsushima Warm Current flowed into an unrestricted well-mixed normal salinity Japan Sea, whereas East Asian winter monsoon (EAWM) conditions dominated MIS 2, MIS 4, MIS 6, and MIS 8 when sea level minima restricted the Japan Sea resulting in low-salinity and oxygen conditions in the absence of Tsushima flow. Reduced oxygen stratified, low-salinity, and higher productivity oceanic conditions characterize Terminations TV, TIII, TII, and TI when East China Sea coastal waters breached the Tsushima Strait. Chinese loess, cave, and Lake Biwa (Japan) and U1427 proxy records suggest EASM intensification during low to high insolation transitions, whereas the strongest EAWM prevailed during lowest insolation periods or high to low insolation transitions. Ice sheet/CO 2 forcing leads to the strongest EAWM events in glacials and enhanced EASM in interglacials. Mismatches between proxy patterns suggest that latitudinal and land/sea thermal contrasts played a role in East Asian monsoon variability, suggesting that a complex interplay between ice sheet dynamics, insolation, and thermal gradients controls monsoonal intensity.

Exceptionally high biosphere productivity at the beginning of Marine Isotopic Stage 11

“…The anomalously high δ 18 O atm at the time of peak biosphere productivity inferred from Δ 17 O of O 2 cannot be explained by a weak monsoon period in opposite to an explanation given for high δ 18 O atm levels observed over the last 800 ka 43 . Indeed, data from other archives rather show a relatively strong East Asia monsoon activity during MIS 11 similarly to what is observed over the last 4 interglacial periods 44,45 . Instead, this high δ 18 O atm values should be interpreted as an increase of the terrestrial vs oceanic productivity ratio expressed in flux of oxygen.…”

Calcareous nannofossil biostratigraphy of the Lower–Middle Pleistocene boundary of the GSSP, Chiba composite section in the Kokumoto Formation, Kazusa Group, central Japan, and implications for sea-surface environmental changes

“…The Tsugaru Current is another surface water mass along the Pacific coast of Japan, which is a southward current flowing along the NE Japanese coast ( Fig. 1; e.g., Qiu 2001;Gallagher et al 2018;Yasuda 2003). This current flows between the coast and the Oyashio Current and originates in the Japan Sea as the Tsushima Current, which branches from the Kuroshio Current around the eastern part of the East China Sea off the west coast of the Tokara Islands, small islands to the south of Kyushu (Fig.…”

Dominance of Shortwave Radiative Heating in the Sea‐Land Breeze Amplitude and its Impacts on Atmospheric Visibility in Tokyo, Japan

“…This region lies in the southeastern part of Japan and can be easily influenced by the East Asia monsoon (Gallagher et al, 2018). Particularly, the great moisture brought by the large‐scale wind field such as summer monsoon can result in a large amount of clouds in the summer.…”