Linkages between East China Sea Deep-sea Oxygenation and the Variability of the East Asian Summer Monsoon and Kuroshio Current over last 400,000 years

Abstract

The East China Sea (ECS) seasonally receives a high organic input due to the terrestrial organic matter influx, which is controlled by the East Asian Summer Monsoon (EASM), and the increased productivity driven by upwelling of the subsurface Kuroshio Current (KC). Changes in benthic foraminiferal assemblage composition in combination with paleoceanographic proxy data (CaCO3 (%), TOC (%), δ 13 Cpf, and δ 18 Obf) are used to reconstruct bottom water oxygenation and organic export flux variability over the last 400 kyr in the ECS. Multivariate analyses of benthic foraminiferal census data identified six biofacies characteristic of varying environmental conditions. These results suggest that enhanced EASM precipitation and KC upwelling directly influenced organic export flux and bottom water oxygen content in the ECS. The ECS bottom water was suboxic during Marine Isotope Stage (MIS) 11 to 8; suboxic to dysoxic between MIS 7 and 6, strongly dysoxic between mid-MIS 5 and 4, and exhibited high variability between MIS 3 and 1. Spectral analysis of relative abundances of representative genera Quinqueloculina (oxic), Bulimina (suboxic), and Globobulimina (dysoxic) reveals a robust 23 kyr signal, which we attribute to precessionally-paced changes in surface productivity and bottom water oxygenation related to KC variability over the past 400 kyr.

Linkages between East China Sea Deep-sea Oxygenation and Variability in the East Asian Summer Monsoon and Kuroshio Current over the last 400,000 years

“…The KC intrusion onto the ECS shelf was stronger during interglacial periods (Vats et al, 2021;MIS 11, 9, 7, and 5), whereas the lowering of sea level adversely influenced KC intrusion in the ECS. For instance, a 43 % reduction in KC inflow occurred during the LGM linked to the…”

“…Benthic foraminiferal percentage abundance data for the last 400 kyr from Site U1429 generated for this study. Major benthic foraminiferal abundance data, Biofacies abundance data and oxic-suboxic-dysoxic benthic foraminiferal species abundance data archived at Mendeley Data (http://dx.doi.org/10.17632/gcsgc2byps.2; Vats et al, 2021).…”