[M-IS15] Paleoclimatology and Paleoceanography

[MIS15-14] Meridional migrations of the Intertropical convergence Zone during the last deglaciation in the Timor Sea detected by geochemical analysis

*Karin Nemoto^1,2, Yusuke Yokoyama^1,2, Horiike Satoshi², Stephen Obrochta³, Yosuke Miyairi¹, Takahiro AZE¹ (1.Atmosphere and Ocean Research Institute, The University of Tokyo, 2.Department of Earth and Planetary Science, The University of Tokyo, 3.Graduate School of International Resource Science, Akita University)

Keywords:ITCZ, deglaciation

High-density radiocarbon dating and improved age-depth modeling methods are advancing our understanding of recent paleoclimate variability. One important development is the increased number of high-precision measurements performed on a daily basis. For example, the single stage Accelerator Mass Spectrometer (AMS) installed at the Atmosphere and Ocean Research Institute (AORI), the University of Tokyo has already analyzed over 16,000 samples since 2013 (Yokoyama et al. 2019; Yokoyama et al. 2022). Thus, we performed extensive radiocarbon analysis on planktonic foraminifera and total organic carbon (TOC) to reconstruct paleo precipitation in the Timor Sea. Increased precipitation enhances input of relatively old, terrestrial carbon, which in turn increases the difference between the calibrated, calendar-year age of TOC and planktonic foraminifera.
The climate in the Timor Sea is characterized by the seasonal precipitation change driven by the meridional migration of the Intertropical Convergence Zone (ITCZ) and monsoon front. The ITCZ shifts meridionally in response to changes in the thermal balance between the northern and southern hemispheres. Thus, reconstruction of paleo precipitation in the Timor Sea will reveal past changes in both regional and global climate, the latter through inference of the ITCZ position.
During Heinrich Stadial 1 and the Younger Dryas, the Timor Sea was wet because of the southerly position of the ITCZ. On the other hand, the northward shift of the ITCZ resulted in the dry condition in the Timor Sea during the Bølling–Allerød warming interval. The ITCZ movement during the last deglaciation reconstructed by extensive radiocarbon dating was consistent with the thermal balance between the northern hemisphere and the southern hemisphere which is mainly controlled by the AMOC strength.