Asian monsoon and oceanic circulation paced sedimentary evolution over the past 1,500 years in the central mud area of the Bohai Sea, China

Abstract

Mud areas within China's marginal seas record critical information about historic environmental changes, which may have contributed to palaeoenvironmental processes and to understand their driving mechanisms. In this study, we investigated the sedimentary characteristics of a gravity core from the Bohai Sea central mud areas, to reveal the interactions between oceanic and climatic changes over the past 15 centuries. Sedimentary and mineral records indicated that the depositional environment and sediment sources were relatively stable, in which the East Asian Summer Monsoon (EASM) and Yellow Sea Warm Current (YSWC) variability can be derived. Based on these results, we found that the winter Arctic Oscillation (wAO) was negatively correlated with the coupled EASM and YSWC changes, namely, a negative (positive) relationship between EASM and YSWC during a positive (negative) wAO. We therefore suggest that over the past 15 centuries, Arctic winter climates may have modulated palaeoenvironmental changes over East Asia continental shelves, via teleconnections with the El Ninõ‐Southern Oscillation (ENSO) and the Kuroshio Current.

A 5000-Year Sedimentary Record of East Asian Winter Monsoon from the Northern Muddy Area of the East China Sea

“…As shown, prior to 2000 y BP, the most dynamic sedimentary process recorded in core ECS-DZ1 did not follow changes in the dominant sedimentary components or dynamics, while after 2000 yr BP, these two parameters were coupled (Figure 3b). For suspended and sea-surface sediments around the Huanghe River mouth [36] and the mud area of the Bohai Sea [12], a good positive correlation between C and Md values was observed, similarly with ones of core Lz908 [37], and ones in the abandoned Huanghe River mouth in the west of the South Yellow Sea [38]. This relationship was consistent in the one of six surface sediments (Figure 3).…”

“…As shown, prior to 2000 y BP, the most dynamic sedimentary process recorded in core ECS-DZ1 did not follow changes in the dominant sedimentary components or dynamics, while after 2000 yr BP, these two parameters were coupled (Figure 3b). For suspended and sea-surface sediments around the Huanghe River mouth [36] and the mud area of the Bohai Sea [12], a good positive correlation between C and Md values was observed,…”

“…Moreover, changes in regional sedimentary dynamics in the study area (Fcomp2) are well correlated to the Bond ice-rafting debris (IRD) events (Figure 5b), which were expressed in the North Atlantic when large numbers of icebergs discharging from the Labrador Sea and Baffin Bay. The Bond IRD events represent a major climate state of high-latitude areas of the Northern Hemisphere on millennial timescales [41,44], and play a critical role in winter climates across the East Asia, e.g., [12,40,45], thus inferring a tightened and rapid atmospheric teleconnection between the North Atlantic and the Asian monsoon [43,46,47]. Similarly, the Fcomp2 can be also linked to the Kuroshio Current (Figure 5c), which is the most important component of the subtropical North Pacific gyre in winters influencing climate changes in the western Pacific [48].…”

“…However, there is no much consistency in the Holocene between the proposed EAWM records in the continental shelves, likely due to the influence of the greater flux by rivers to the continental shelves in summers, which is another key factor influencing sedimentary dynamics in these muddy areas. Hence, some researchers claimed that the EASM could be a unignored factor dominating sedimentary dynamics in the muddy areas of the Bohai Sea and the South Yellow Sea [12,15].…”

“…For instance, Zhang, et al [11] combined sedimentary dynamics and geochemical properties of the north inner continental shelf of the ECS and quantitatively reconstructed the East Asian winter monsoon (EAWM) in the last century. Lyu, et al [12] claimed a mechanism that how Arctic winter climates modulated the relationship between the East Asian summer monsoon (EASM) and the Yellow Sea Warm Current (YSWC) over the past 1500 years, by an integration of sedimentary dynamics and mineralogical properties of the central Bohai Sea. These two new records are somehow conflicted-whether the EAWM or the EASM dominates the sedimentary processes of muddy areas on the continental shelves-and the potential mechanism has been hotly debated in the past decade, because of the large difference between published monsoonal proxies [1,4,13].…”