Seasonal scale records of hydroclimate and temperature derived from clumped isotopes of land snail shells from the Chinese Loess Plateau

Quantitative reconstructions of past precipitation and temperature variations at the seasonal scale are essential for understanding East Asian Monsoon (EAM) dynamics. However, archives capable of capturing seasonal climate signals on land are limited. Here, we present high-resolution stable oxygen isotope (δ¹⁸O_shell) and carbonate clumped isotope (Δ₄₇) data from modern and fossil land snail shells collected from the eastern (Lingbao, LB) and western (Yuanbao, YB) edge of the Chinese Loess Plateau (CLP).

The δ¹⁸O_shell of modern snails similarly reflect the seasonal variation in precipitation oxygen isotopic signals at both locations. The Δ₄₇-derived temperatures for the same snails indicate that the seasonal temperature difference (summer vs. winter) is larger at YB than LB, aligning with modern observations from the western edge of the CLP, where a higher elevation results in a larger seasonality. The averaged whole shell Δ₄₇-derived temperatures (T₄₇) from modern Cathaica pulveritrix shells at LB and their related Cathaica richthofeni snails at YB resemble growing season temperatures. Interestingly, the T₄₇ of shells of three smaller snail species, Pupilla muscorum, Kaliella lamprocystis, and Vallonia sp. are substantially (up to 10 ºC) lower than those of C. richthofeni from the same site. The temperature difference between snail species and among specimens suggests that optimal living conditions and micro-environments likely play a key role in the temperature signal recorded in the snail shells.

Fossil snails from LB show a larger variability in δ¹⁸O_shell  during the Last Glacial Maximum (LGM, 19–18 ka), with wet season values approximately 3‰ more depleted than modern shells. In contrast, the seasonal temperature difference in fossil snails is smaller than in their modern counterparts, and growing season temperatures are ~10 °C lower than the present at LB. Fossil shells from YB also have a more negative δ¹⁸O_shell during the last deglaciation (14‒13 ka) than their modern counterparts. Similar to LB snails, the whole shell T₄₇ of fossil snail shells at YB indicates that growing season temperatures were ~10 °C lower than recorded by their modern counterparts, and the temperature variability on a seasonal scale is smaller than in modern snails. The relatively large variability, negative δ¹⁸O_shell values and low T₄₇ values in fossil shells suggests weaker evaporation or longer water vapor transportation under glacial conditions. While snail shells can capture high-resolution climate signals, variations in living conditions and micro-environments among snail species and specimens should be considered in future Δ₄₇-based temperature studies and their applications.