C01_P07

Paleoclimate study in the Indonesian throughflow region using carbon and beryllium isotopes

Nemoto K¹, Yokoyama Y¹, Horiike S¹, Obrochta S², Miyairi Y¹, Aze T¹

¹The University Of Tokyo, Kashiwa, Japan, ²Akita University, Akita, Japan

The Indonesian throughflow (ITF), the only pathway between the Pacific and Indian Oceans, transports relatively cool, less saline water from the Pacific to the Indian Ocean. Air-sea interactions change dynamically in correspondence with ITF variability, which in turn affects climate (Song & Gordon, 2004). It is also known that the strength of the ITF fluctuates with glacial cycles (Hendrizan et al., 2017; Fan et al., 2018) Thus, reconstruction of past changes in ITF strength is important to better understand global climate. Even though several previous studies address the reconstruction of past ITF variability, more spatially high-resolution data are needed considering the complex pathway of the ITF.

In this study, two cosmogenic isotopes are measured to reconstruct past climate change around the Timor Sea, which is one of the ITF pathways. Radiocarbon dating was performed on planktonic foraminifera and total organic carbon. The offset between each age and carbon nitrogen ratio provides information on past changes in terrigenous material movement. In addition, beryllium 10, another cosmogenic nuclide, and its stable isotope beryllium 9, sourced from weathering, are measured. The effect of environmental components such as grain size can be removed by measuring these two isotopes (Simon et al., 2016). This is the first study to apply multiple cosmogenic nuclides (carbon 14 and beryllium 10) to reconstruct the paleoclimate of the ITF region.