Global cooling events of the Late Holocene preserved in the coastal sediments in the southern Far East of Russia

Multy-proxy studies of the lagoon terrace in the head of the Amur Bay made it possible to identify sharp short-term cooling events during ~4450, 2870–2510, 1740–1200, and 680–380 yr BP, and compared them with cold events in other regions around the world. The reconstructions are based on results of diatom, botanical, and palynological analyzes. The Becon age model is based on radiocarbon dating and tephrostratigraphy. Tephra B-Tm from the caldera-forming Baitoushan volcano eruption was found in the section of the peat mire. The section selected to serve as a natural archive has its own specifics. In contrast to the mountainous areas and river basins, where the climate became dry 3320–3050 years ago due to a sharp decrease in the intensity of the summer monsoon, coastal lacustrine-swamp sequences had been developing in constantly waterlogged conditions. This made it possible to identify short-term dry events that well correlate with the global climatic rhythm caused by decrease in solar radiation. The decrease in moisture was closely related to the influence of the ocean: the intensity of tropical cyclogenesis, which is controlled by the activity of El Niño. The shallowing of the lagoon during the decline of low-amplitude transgression, intensified by the weakening of the summer monsoon, led to a change in terrigenous sedimentation to organogenic at about 3460 years ago. The cooling during 2870–2510 years ago had the most complex structure with sharp changes in moisture. Change in the course of swamp-forming processes around 1740 years ago associated with the activation of floods, which caused periodic flooding of the peat mire in the vast wetland near the Razdolnaya River mouth, led to the disappearance of the trees and the development of a grass swamp. In general, regional conditions were dry until the Medieval Warm Period. The landscapes responded to cooling by decreasing the role of broad-leaved trees in the forest vegetation of the low mountains, and increase of plants prefering less water-saturated habitats in the coastal plant communities. Of the cold events, the exception is the Little Ice Age, which was wet and characterized by frequent floods. The meridional transfer of moist air masses from the ocean to the continent became more active during that time.