75,000 years of hydroclimate and temperature variations in East Asia derived from snail shell clumped isotopes

Abstract

Changes in past East Asian climate and monsoon intensity have been inferred from a wide variety of paleoclimate archives. However, quantitative reconstruction of land surface temperatures in East Asia remains sparse. Here we present a 75-kyr temperature record derived from the carbonate clumped isotope composition (Δ47) of land snail shells from a loess-paleosol sequence at Yuanbao, on western edge of the Chinese Loess Plateau (CLP). Modern growing season (mid-April to September) temperature based on Δ47 (T47) is 21.2 ± 1.2 °C. The T47 record reveals that there are certain periods where land surface temperatures were lower: the last glacial maximum (LGM) was ∼7 °C colder, Marine Isotope Stage 3 (MIS3) ∼5 °C and MIS4 ∼6 °C, but also the mid-Holocene was ∼9 ℃ colder than present day. Temperatures similar to present day occurred during Northern Hemisphere Summer Insolation (NHSI) minima within MIS3 and the Bølling-Allerød (BA). Monsoon precipitation reconstructions based on organic and inorganic geochemical proxies from the same loess-paleosol section indicate that these warm periods are characterized by relatively dry conditions. This is further supported by the relative enrichment in the temperature-independent oxygen isotope composition of snail body water (δ18Obw) during these time intervals, reflecting a negative moisture balance. In contrast, the unexpected low T47 for the mid-Holocene could be the result of wet conditions. Our record thus suggests that soil moisture availability exerts a strong influence on land surface temperatures recorded by snails stored in loess archives.