Timing and Mechanisms of the Formation of the Dark Layers in the Sea of Japan During the Last 40 kyr

S Gorbarenko,Y Liu,Y Wu,A Bosin,L Hu,Y Vasilenko,A Artemova,E Yanchenko,X Shi,J Zou

doi:10.3389/feart.2021.647495

Abstract

The marginal location of the Sea of Japan and its constrained water exchange with the western Pacific make this sea a subtle subject for the investigation of orbital and suborbital climate changes. However, the response of this unique basin to the climate and sea level changes at the end of the last glaciation and deglaciation and during the Holocene is not fully understood. We provided detailed reconstructions of the dark layers including the timing and mechanisms responsible for their formation, during the last 40°kyr, based on the multiproxy correlation of three cores from the northern and central parts of the sea with well-dated δ18O records of the Greenland ice and China cave stalagmites. High resolution color photo lightness, the conventional color parameters L* and b*, AMS 14C data, chlorin and carbonate calcium content and pollen climate parameters allowed the correlation of the DLs of these cores with Greenland interstadials (GI), Heinrich stadials (HS) and summer East Asian monsoon intensity. DLs 9, 8, 7, and 6, formed after Heinrich stadials 4 (38.5–39.5°ka), were triggered by GIs 8, 7, 6 and 5, coeval with the intensification of the East Asian summer monsoon and the increase of surface water stratification and productivity. The long-lasting GI 8, accompanied by significant climate warming, led to the formation of the more intense DL 9. The accumulation of DL five was forced by a rapid global sea level fall, coeval with cold HS 3, due to the decrease of saline Tsushima Current water input into the sea, increased surface water stratification and a drop in deep water ventilation. DL four was probably launched by GI 3 and summer East Asian monsoon intensification. Further falls in global sea level during the last glacial maximum led to the formation of DLs 3 and 2 during the periods 27.0–24.2°ka and 23.5–17.0°ka, respectively. DL 1 was associated with significant summer East Asian monsoon intensification and environmental warming at the onset of the Holocene.

Highlights

The semi-closed Sea of Japan is connected with the Western Pacific through shallow straits
In addition to the mentioned proxies of the studied cores, we presented here the pollen indices Kp and Kp* for cores LV32-33 and LV53-23-1, respectively, which were earlier presented in Gorbarenko et al (2014) and Gorbarenko et al (2015); they allowed us to correlate the formation of dark layers (DL) with global climate changes in the Northern Hemisphere recorded in the δ18O curves of the Greenland ice and East Asian monsoon
Highly resolved color PL, the conventional color parameters L* and b*, AMS 14C data, chlorin and CaCO3 content and pollen climate parameters allowed the correlation of the DLs in three cores from the northern and central parts of the Sea of Japan with well-dated Greenland interstadials (GI), Heinrich stadials (HS), the summer East Asian monsoon intensity and sea level changes

Summary

Introduction

The semi-closed Sea of Japan is connected with the Western Pacific through shallow straits. Timing of the Dark Layers in the Sea of Japan glacial maximum (LGM) Gorbarenko, (1983); Gorbarenko, (1993); Oba, (1984); Oba et al (1991); Keigwin and Gorbarenko, (1992); Tada et al (1995) et so on) Such lightening δ18O values of planktic foraminifera is contrary to heavy carbonate δ18O values in the records of the world ocean over the marine isotopic stage (MIS) 2 (Martinson et al, 1987; Lisiecki and Raymo, 2005) and may be explained only by decrease in δ18O and salinity of the Sea of Japan surface water. A color parameter like b*, responsible for the organic content in sediments, was successfully used to correlate the millennial-scale paleo-oceanography events of the East Asian marginal Okhotsk and Bering seas with DO cycles (Nürnberg and Tiedemann, 2004; Riethdorf et al, 2013; Gorbarenko et al, 2019)

Methods

Discussion

Conclusion