Vegetation evolution in response to climate change and rapid sea-level rise during 8.2–7.0 cal ka BP: Pollen evidence from the northwest coast of Bohai Bay, north China

Abstract

To understand vegetation dynamics and their response to climate changes and sea-level rise (SLR) on the northern coast of the Bohai Sea during a marine transgression period (8.2–7.0 cal ka BP), we obtained two sedimentary cores (HG01 and HG02) with high-resolution accelerator mass spectrometry carbon-14 (14C) data from the coastal plain of Bohai Bay in northeastern China. A general warming and wetting trend from 8190 to 7920 cal a BP was indicated by the greater abundance of deciduous broadleaved forest, which showed that the Asian summer monsoon was stronger over this period. The abundance of deciduous broadleaved trees was relatively high, which revealed that the climate was relatively warm and wet and that the Asian summer monsoon was strong, during the periods of 7920–7690 cal a BP and 7230–7020 cal a BP. Broadleaved tree abundance decreased over the intervening period—from 7610 to 7230 cal a BP—suggesting a declining monsoon, and relatively cool, dry climate. The abrupt cooling event from 7460 to 7230 cal a BP may have been a global event, closely related to the decrease in solar activity and rapid SLR before 7460 cal a BP. The results also showed that the large number of halophytes mainly Chenopodiaceae, sharply increased at times, mirroring four SLR fluctuation periods: 7940–7860 cal BP, 7760–7700 cal BP, 7560–7460 cal BP, and 7230–7130 cal BP. SLR in Bohai Bay occurred during warm and wet climate periods, and the phased SLR observed during ~7.9–~7.1 cal ka BP may have been the local manifestation of a global event.