Late Pleistocene to early Holocene ENSO-related hydroclimatic changes revealed by palynological records from the coastal Xixi Basin, eastern China

We report a palaeontological record for the last 37.0 cal kyr BP in the Xixi Basin, eastern China, to better understand the correlation between hydroclimatic change and vegetation history during the late Pleistocene to early Holocene. Principal component analysis based on the 25 main palynological taxa indicated that dominant taxa fall into three groups: conifers that preferred dry conditions on the left of leading principal component (PC) 1, ferns and wetland communities associated with a humid climate responding to the positive loading of PC1, and Quercus-dominated communities principally corresponding to PC2. Based on this analysis, hydroclimatic conditions were relatively warm/dry during the latter Marine Isotope Stage (MIS) 3 with a high abundance of conifers. This was followed by a generally cold/wet MIS 2 with expansion of ferns and herbs, and a warm/dry MIS 1 with more evergreen species. The sporadic occurrence of evergreen species and drier conditions since about 19.0 cal kyr BP coincides with the beginning of the last deglaciation. An increase in sedimentary accumulation rates and changes in vegetation components at the onset of the Holocene are likely related to maximum transgression. Wet conditions coincide with several cold intervals, including Heinrich events and the Last Glacial Maximum. The overall warm/dry and cold/wet climatic patterns agree well with the palaeoclimatic records elsewhere in the middle Yangtze region, showing similar hydroclimatic forcing mechanisms related to the migration of the Meiyu Front modulated by the El Niño-Southern Oscillation (ENSO) activities. Cold/wet conditions probably correspond to enhanced ENSO and reduced insolation while warm/dry conditions correspond to dampened ENSO and increased insolation. The extremely humid conditions that occur during cold events may result from the combined effects of the Atlantic Meridional Overturning Circulation and ENSO. These results expand our understanding of the monsoonal hydroclimate in eastern China during the late Quaternary period.