Precession and atmospheric CO2 modulated variability of sea ice in the central Okhotsk Sea since 130,000 years ago

• Published in: Earth and planetary science letters Vol. 488; pp. 36 - 45
• Main Authors: Lo, Li, Belt, Simon T., Lattaud, Julie, Friedrich, Tobias, Zeeden, Christian, Schouten, Stefan, Smik, Lukas, Timmermann, Axel, Cabedo-Sanz, Patricia, Huang, Jyh-Jaan, Zhou, Liping, Ou, Tsong-Hua, Chang, Yuan-Pin, Wang, Liang-Chi, Chou, Yu-Min, Shen, Chuan-Chou, Chen, Min-Te, Wei, Kuo-Yen, Song, Sheng-Rong, Fang, Tien-Hsi, Gorbarenko, Sergey A., Wang, Wei-Lung, Lee, Teh-Quei, Elderfield, Henry, Hodell, David A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.04.2018; Elsevier
• Subjects: Astrophysics; greenhouse gases; insolation; Okhotsk Sea; Physics; precession cycle; sea ice; Okhotsk Sea; insolation; greenhouse gases; precession cycle; sea ice
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2018.02.005

Recent reduction in high-latitude sea ice extent demonstrates that sea ice is highly sensitive to external and internal radiative forcings. In order to better understand sea ice system responses to external orbital forcing and internal oscillations on orbital timescales, here we reconstruct changes in sea ice extent and summer sea surface temperature (SSST) over the past 130,000 yrs in the central Okhotsk Sea. We applied novel organic geochemical proxies of sea ice (IP25), SSST (TEXL86) and open water marine productivity (a tri-unsaturated highly branched isoprenoid and biogenic opal) to marine sediment core MD01-2414 (53°11.77′N, 149°34.80′E, water depth 1123 m). To complement the proxy data, we also carried out transient Earth system model simulations and sensitivity tests to identify contributions of different climatic forcing factors. Our results show that the central Okhotsk Sea was ice-free during Marine Isotope Stage (MIS) 5e and the early-mid Holocene, but experienced variable sea ice cover during MIS 2–4, consistent with intervals of relatively high and low SSST, respectively. Our data also show that the sea ice extent was governed by precession-dominated insolation changes during intervals of atmospheric CO2 concentrations ranging from 190 to 260 ppm. However, the proxy record and the model simulation data show that the central Okhotsk Sea was near ice-free regardless of insolation forcing throughout the penultimate interglacial, and during the Holocene, when atmospheric CO2 was above ∼260 ppm. Past sea ice conditions in the central Okhotsk Sea were therefore strongly modulated by both orbital-driven insolation and CO2-induced radiative forcing during the past glacial/interglacial cycle. •The first orbital timescale proxy-model sea ice-sea surface temperature records from the northwestern subarctic Pacific Ocean.•Strong precession forcing controlled and sea ice variations are modulated by greenhouse gas radiative forcing.•Sea ice remained free in the central Okhotsk Sea during MIS 5e due to high greenhouse gas radiative forcing.