[M-IS06] [EE] Evolution and variability of Asian Monsoon and its linkage with Cenozoic global cooling

[MIS06-P01] The effect of insolation and greenhouse gases on sea ice variations in the Okhotsk Sea during the past 180,000 years

*Li Lo^1,2, Simon T. Belt³, Julie Lattaud⁴, Axel Timmermann^5,6, Christian Zeeden⁷, Stefan Schouten^4,8, Lukas Smik³, Tobias Friedrich⁶, Patricia Cabedo-Sanz³, Jyh-Jaan Huang⁹, Liping Zhou¹⁰, Tsong-Hua Ou¹¹, Yuan-Ping Chang¹², Liang-Chi Wang¹³, Yu-Min Chou⁹, Chuan-Chou Shen⁹, Min-Te Chen¹⁴, Kuo-Yen Wei⁹, Sheng-Rong Song⁹, Tien-Hsi Fang¹⁴, Sergey A. Gorbarenko¹⁵, Wei-Lung Wang¹⁶, Teh-Quei Lee¹⁷, Henry Elderfield¹, David A. Hodell¹ (1.Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, 2.State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochecmistry, Chinese Academy of Sciences, 3.Biogeochemical Research Centre, School of Geography, Earth and Environmental Sciences, Plymouth University, 4.NIOZ, Royal Netherlands Institute for Sea Research, Department of Marine Microbiology and Biogeochemistry, and Utrecht University, 5.nstitute of Basic Science, Center for Climate Physics, Pusan National University, 6.International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii, 7.Lehrstuhl für Physische Geographie und Geoökologie, RWTH Aachen University, 8.Faculty of Geosciences, Department of Earth Sciences, Utrecht University, 9.Department of Geosciences, National Taiwan University, 10.College of Urban and Environmental Sciences, Peking University, 11.Institute of Applied Mechanics, National Taiwan University, 12.Department of Oceanography, National Sun Yat-sen University, 13.Collection Management Department, National Taiwan Museum, 14.Institute of Applied Geosciences, National Taiwan Ocean University, 15.V.I. II'ichev Pacific Oceanological Institute, Far East Branch Russian Academy of Science, 16.Department of Biology, National Changhua University of Education, 17.Institute of Earth Sciences, Academia Sinica)

Keywords:Sea ice, Seasonality, Orbital pacing, CO2 radiative forcing

Sea ice is a critical and sensitive component of the Earth’s climate system, and has undergone dramatic reductions in extent and thickness for much of the Arctic in the last few decades (Budikova, 2009; Bader et al., 2011). However, studies covering orbital timescales are still lacking, largely due to the lack of a reliable sea ice proxy in the subarctic regions, or marine sedimentary archives with sufficient age control and temporal resolution. Here we reconstruct high-resolution subarctic Pacific sea ice and summer sea surface temperature records for the past 180,000 years using novel organic geochemical proxies in the central Okhotsk Sea. Our sea ice reconstruction shows significant precession (23-kyr) cycles, which are coupled to local autumn insolation during intervals of low-mid atmospheric CO₂ concentrations (<~260 ppm). We also find that the Okhotsk Sea was ice-free during the mid-late Holocene and throughout the penultimate interglacial (Marine Isotope Stage 5e) when CO₂ concentration exceeded this threshold, suggesting that both insolation and atmospheric CO₂ levels are responsible for controlling sea ice variation in the Okhotsk Sea on orbital timescales. A proxy-model comparison reveals general agreement between the two approaches.