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Speleothem δ18O records from central southern China have long been regarded as a key benchmark for Asian summer monsoon intensity. However, the similar δ18O minima observed among precession minima and their link to seasonal precipitation mixing remains unclear. Here, we present a 400,000-y record of summer precipitation δ18O from loess microcodium, which captures distinct precession cycles similar to those seen in speleothem δ18O records, particularly during glacial periods. Notably, our microcodium δ¹⁸O record reveals very low-δ¹⁸O values during precession minima at peak interglacials, a feature absent in speleothem δ¹⁸O records from central southern China. This discrepancy suggests that the mixed summer and nonsummer climatic signals substantially influence the speleothem δ¹⁸O records from central southern China. Proxy-model comparisons indicate that the lack of very low-δ¹⁸O values in speleothem δ¹⁸O records is due to an attenuated summer signal contribution, resulting from a lower summer-to-annual precipitation ratio in southern China at strong monsoon intervals. Our findings offer a potential explanation for the long-standing puzzle of the absence of 100- and 41-kyr cycles in speleothem δ¹⁸O records and underscore the critical role of seasonality in interpreting paleoclimatic proxies in central southern China. These insights also have broader implications for interpreting speleothem δ¹⁸O records globally, advocating for a more multiseason interpretive framework. 

Abstract. The mid-Pliocene (∼3 Ma) is one of the most recent warm periods with high CO2 concentrations in the atmosphere and resulting high temperatures, and it is often cited as an analog for near-term future climate change. Here, we apply a moisture budget analysis to investigate the response of the large-scale hydrological cycle at low latitudes within a 13-model ensemble from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). The results show that increasedatmospheric moisture content within the mid-Pliocene ensemble (due to thethermodynamic effect) results in wetter conditions over the deep tropics,i.e., the Pacific intertropical convergence zone (ITCZ) and the MaritimeContinent, and drier conditions over the subtropics. Note that the dynamiceffect plays a more important role than the thermodynamic effect in regionalprecipitation minus evaporation (PmE) changes (i.e., northward ITCZ shiftand wetter northern Indian Ocean). The thermodynamic effect isoffset to some extent by a dynamic effect involving a northward shift of the Hadleycirculation that dries the deep tropics and moistens the subtropics in theNorthern Hemisphere (i.e., the subtropical Pacific). From the perspective ofEarth's energy budget, the enhanced southward cross-equatorial atmospherictransport (0.22 PW), induced by the hemispheric asymmetries of theatmospheric energy, favors an approximately 1∘ northward shift ofthe ITCZ. The shift of the ITCZ reorganizes atmospheric circulation,favoring a northward shift of the Hadley circulation. In addition, theWalker circulation consistently shifts westward within PlioMIP2 models,leading to wetter conditions over the northern Indian Ocean. The PlioMIP2ensemble highlights that an imbalance of interhemispheric atmospheric energyduring the mid-Pliocene could have led to changes in the dynamic effect,offsetting the thermodynamic effect and, hence, altering mid-Pliocenehydroclimate.