Orbital and Millennial Variations in Sea Ice in the Southwestern Okhotsk Sea Since the Last Interglacial Period and Their Implications

Anqi Wang,Yanguang Liu,Yonghua Wu,Jianjun Zou,Sergey A Gorbarenko,Xuefa Shi,Kunshan Wang,Zhengquan Yao

doi:10.3389/feart.2021.710797

Abstract

Sea ice in the Okhotsk Sea plays a significant role in global climate change. However, the history and mechanism of changes in sea ice spanning the last glacial cycle remain controversial. In this study, an 8.8 m core (LV55-40-1) was recovered from the southwestern Okhotsk Sea that contains a continuous sea ice record over the past ∼110 kyr. The sand fraction and dropstones were used as ice-rafted debris proxies to reconstruct the history of sea ice variations over the last ∼110 kyr and to determine the underlying causes on orbital and millennial timescales. Sea ice expansions occurred during MIS 5b, MIS 4, mid-MIS 3, and early MIS 1, which were controlled mainly by decreased autumn insolation on an orbital timescale. Superimposed on the orbital-scale changes, millennial-scale variations in sea ice were also observed, with 19 expansion events that coincided with cold Dansgaard-Oeschger stadials. Millennial scale sea ice variations were most likely controlled by both the Arctic oscillation and the East Asian summer monsoon. During periods of negative Arctic oscillation patterns, decreased air temperatures over the Okhotsk Sea caused more active sea ice formation. Such conditions could have been reinforced, by a reduced influence of warm advection at the surface of the Okhotsk Sea caused by decreased discharge from the Amur River that resulted from a weakened East Asian summer monsoon during cold stadials.

Highlights

Sea ice is widespread in the subarctic North Pacific, and its expansion and retreat impact local and global climate changes by modulating the sea ice-induced albedo and energy budgets at both high and low latitudes (Turner et al, 2015; Serreze et al, 2016)
The chlorin content in the Okhotsk Sea increased during Dansgaarde-Oeschger interstadials (DOIs), and have been used to construct high-resolution age models in the Okhotsk Sea (Gorbarenko et al, 2007; Gorbarenko et al, 2009; Gorbarenko et al, 2010; Gorbarenko et al, 2012; Vasilenko et al, 2017; Gorbarenko et al, 2020)
We reconstructed the history of sea ice variations in the southwestern Okhotsk Sea over the last ∼110 kyr and investigated the factors controlling sea ice changes on orbital and -millennial timescales based on the icerafted debris (IRD) proxy

Summary

Introduction

Sea ice is widespread in the subarctic North Pacific, and its expansion and retreat impact local and global climate changes by modulating the sea ice-induced albedo and energy budgets at both high and low latitudes (Turner et al, 2015; Serreze et al, 2016). Previous studies have suggested that sea ice variations on orbital scales are controlled largely by glacial–interglacial cycles (Gorbarenko et al, 2002; Gorbarenko et al, 2003; Nürnberg and Tiedemann, 2004; Sakamoto et al, 2005). Sakamoto et al (2006) inferred that discharge from the Amur River and polar atmospheric dynamics were potential factors that control sea ice expansion on millennial scales. The southwestern Okhotsk Sea is subject to the influence of fluvial discharge via the East Sakhalin Current (Zhabin et al, 2010) This is an ideal region for studying the history of sea ice cover and its potential connections with fluvial discharge. We attempted to determine the dominant factors that control sea ice variations at orbital and -millennial timescales during the last glacial cycle

Methods

Results

Discussion

Conclusion