PhD defence: Quantitative reconstruction of late Quaternary climate in monsoonal East Asia: Validation and application of tetraether membrane lipid proxies and clumped isotope thermometry

Global warming induced by anthropogenic activities, particularly the emission of greenhouse gases such as CO2, stands as one of the most urgent challenges for our society. The resulting extreme climate events threaten food and water security and endanger human lives.

The East Asian Monsoon (EAM) is one of the strongest monsoon systems and controls the water supply to over 20% of the world’s population. Theoretically, the EAM will strengthen in response to ongoing global warming, however, instrumental data indicates that the EAM has been weakening and becoming more erratic since the 1970s. Enhancing our understanding of past EAM conditions can provide valuable insights for the future and improve the development of effective mitigation strategies.

In this study, two independent paleothermometers (membrane-spanning lipids of soil bacteria and carbonate clumped isotopes of fossil snail shells) are applied into a loess-paleosol sequence located on the western edge of the Chinese Loess Plateau where is dominated by the EAM. The absolute temperature and precipitation records over the late Quaternary indicates that the simulated temperatures are highly impacted by soil moisture availability and growing season length of soil bacteria and snails. Other than that, before apply the reconstructed temperatures to paleoclimatic context, it is important to thoroughly assess the proxy. This thesis has also demonstrated the importance of combining multiple proxies for precisely reconstructing paleoclimate variations.