Oak pollen infrageneric classification-based winter temperature reconstruction since the marine isotope stage 5 in Southeast China

Abstract

Quantitative reconstructions of Quaternary terrestrial temperatures in the western Pacific are scarce, resulting in a gap in synchronous comparisons between marine and terrestrial paleoclimate proxies. This study reconstructs winter temperatures along the southeastern coast of China since late Marine Isotope Stage (MIS) 5 using infrageneric classification of Oak (Quercus L.) pollen—a dominant broad-leaved taxon in East Asia. A total of 861 oak pollen grains from 15 topsoil samples spanning 11 latitudes were analyzed using scanning electron microscopy, identifying five ornamentation types—rod-like, rod-like vertical, rod-like masked, verrucate, and scattered verrucate—linked to four taxonomic sections. Redundancy analysis showed strong correlations between ornamentation type ratios and the Mean Temperature of the Coldest Quarter (MTCQ). This was further supported by a MaxEnt species distribution model, highlighting MTCQ as a key driver of deciduous oak distribution along the north-south gradient. Using the Transformation Function Method, modern pollen-MTCQ relationships were applied to 967 fossil oak pollen grains from two coastal drilling cores. Results reveal fluctuating MTCQ over time: slightly cooler conditions during late MIS5, marginally warmer conditions in early and middle MIS3, and significant cooling events in late MIS3 (−3.6 °C with 1.96 °C root mean square error) and the early Holocene. These late MIS3 cooling events align with changes in the Atlantic Meridional Overturning Circulation (AMOC), indicating that East Asian winter temperatures are sensitive to AMOC intensity. Additionally, tropical climate processes, reflected in shifts in the western-to-eastern Pacific temperature gradient, appear to have influenced regional climate dynamics during MIS3. Therefore, this study highlights the complex teleconnections between high- and low-latitude climate systems, offering valuable insights into past climate variability. Furthermore, the MTCQ reconstruction derived from oak pollen data exhibited strong consistency with an independent, full pollen-based reconstruction. This close correspondence suggests that oak pollen can be a valuable proxy for paleoclimate estimation, supporting its utility in paleoclimatic studies.