Spatial and temporal variability of Terminal Classic Period droughts from multiple proxy records on the Yucatan Peninsula, Mexico

Abstract. The Terminal Classic Period (TCP, 800–1000 A.D.) coincides with the collapse of the Maya Civilization on the Yucatan Peninsula, a period of rapid population decline that has been attributed to extended and widespread droughts. This study uses multiple proxy records from the Yucatan Peninsula to collectively analyze drought occurrence across the region during this time. We use a changepoint analysis to identify periods of significant changes in the statistical properties (mean and variance) of 23 proxy records and classify evidence of drought based on four criteria: (1) a changepoint in mean and variance during the TCP, (2) a change towards more arid conditions during the TCP, (3) a change greater than 20 % from the time-series mean, and (4) having a mean during the TCP that is significantly different from the time-series mean. Our analysis shows that five records met all inclusion criteria for showing definitive evidence of drought during the TCP, and these are located in the northwest, northeast, and north-central regions of the Yucatan Peninsula. Many of these records showed some evidence of drought (meeting some but not all criteria), but some showed evidence of drought occurring earlier than the TCP (in the northeast of the Yucatan Peninsula) and later than the TCP (in the south of the Yucatan Peninsula). We also conducted a changepoint analysis on reconstructions of three modes of climate variability known to affect the movement of the Intertropical Convergence Zone (ITCZ). Our comparison suggests that during the first half of the TCP, the Pacific Decadal Oscillation (PDO), El Niño Southern Oscillation (ENSO), and Atlantic Multidecadal Oscillation (AMO) were all in positive phase, which may have pushed the ITCZ southward during the winter months and enhanced aridity during the dry season. However, our analysis suggests that the position of the ITCZ was not the sole driver of the TCP droughts, as these conditions existed over the Yucatan Peninsula prior to the TCP as well. This study highlights the complexity of the spatial and temporal variability of these droughts, and points to the need for further study to identify the mechanisms responsible for the TCP droughts.