| Summary: | Abstract The regional impact of abrupt glacial climate variability remains poorly constrained for arid southwestern Asia, particularly winter dynamics during Marine Isotope Stage 3, due to limited paleoarchives in the Middle East. Here, we present novel continuous speleothem records of δ 18 O and δ 13 C for Southwestern and Central Iran, spanning the interval ~50-30 ka. Stable-isotope signals in the two stalagmites are generally uncorrelated and do not exhibit a consistent response to Greenland stadials or interstadials; however, both show a positive δ 18 O excursion that coincides with Heinrich event 4. We explore the potential mechanisms for intermittent coupling of speleothem δ 18 O across Iran through isotope-enabled atmospheric modelling outputs, from which we utilize the spatial δ 18 O gradient as a proxy for wintertime westerly vs. southerly jet strength. Our results suggest that during Heinrich event 4 and several Greenland stadials, stronger westerly winds enhanced Mediterranean moisture contributions to both sites and reduced aridity in southern Iran. Samples were collected in February (sample SIB-7) and July (sample KAH-3) 2019 in southwestern and central Iran (southwestern Asia) from Sibaki and Kahak Caves, respectively. Stalagmites SIB-7 and KAH-3 were cut along their growth axes and the polished slabs were inspected for possible hiatuses. A total of 24 and 12 samples were drilled for 230Th dating along individual growth lamina on SIB-7 and KAH-3, respectively. Samples were chemically processed at the Department of Earth Sciences, University of Oxford. The process included spiking with a 229Th-236U spike, dissolving in HNO3, and refluxing overnight on hot plates to reach the spike-sample equilibrium. U and Th chemical separation were performed following the procedure of Edwards et al. (1987) and the samples were analyzed on a Nu Plasma multi-collector inductively coupled plasma mass spectrometer following the procedure described in Carolin et al. (2019). The 230Th ages and their 95% confidence ...
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