2021.3.13（Sat）Awards and Commendations
【Press release】Rapid coupling between solid earth and ice volume during the Quaternary: Yusuke Kuwahara (D1), Department of Systems Innovation, and Professor Yasuhiro Kato, Frontier Research Center for Energy and Resources/Department of Systems Innovation, and other researchers
Rapid coupling between solid earth and ice volume during the Quaternary: Yusuke Kuwahara (1st year of the doctoral course), Kazutaka Yasukawa (Lecturer), Koichiro Fujinaga (Researcher), Junichiro Ohta (Assistant Professor), Kentaro Nakamura (Associate Professor), Yasuhiro Kato (Professor) and other researchers.
The solid earth plays a major role in controlling Earth’s surface climate. Volcanic degassing of carbon dioxide (CO2) and silicate chemical weathering are known to regulate the evolution of climate on a geologic timescale (> 106 yr), but the relationship between the solid earth and the shorter (< 105 yr) fluctuations of Quaternary glacial–interglacial cycles is still under debate. Here we show that the seawater osmium isotope composition (187Os/188Os), a proxy for the solid earth’s response to climate change, has varied during the past 300,000 years in association with glacial–interglacial cycles. Our marine Os isotope mass-balance simulation reveals that the observed 187Os/188Os fluctuation cannot be explained solely by global chemical weathering rate changes corresponding to glacial–interglacial climate changes, but the fluctuation can be reproduced by taking account of short-term inputs of (1) radiogenic Os derived from intense weathering of glacial till during deglacial periods and (2) unradiogenic Os derived from enhanced seafloor hydrothermalism triggered by sea-level falls associated with increases of ice sheet volume. Our results constitute the first evidence that ice sheet recession and expansion during the Quaternary systematically and repetitively caused short-term (< 105 yr) solid earth responses via chemical weathering of glacial till and seafloor magmatism. This finding implies that climatic changes on < 105 yr timescales can provoke rapid feedbacks from the solid earth, a causal relationship that is the reverse of the longer-term (> 106 yr) causality that has been conventionally considered.