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.
The Huanghe River (Yellow River) is the most sediment laden river system in the world, and many efforts have been conducted to understand modern deltaic evolution in response to anthropological impacts. However, the natural background and its linkage to climatic changes are less documented in previous studies. In this work, we studied the sediments of core YDZ–3 and marine surface samples by grain-size analysis to retrieve Holocene dynamics of the Huanghe River delta in detail. The main findings are as follows: The mean value of sediment grain size of the studied core is 5.5 ± 0.9 Φ, and silt and sand contents are 5.2 ± 2.3% and 8.2 ± 5.3%, respectively, while the variance of clay particles is relatively large with an average value of 86.4 ± 8.5%. All grain-size data can be mathematically partitioned by a Weibull-based function formula, and three subgroups were identified with modal sizes of 61.1 ± 28.9 μm, 30.0 ± 23.9 μm, and 2.8 ± 1.6 μm, respectively. There are eight intervals with abrupt changes in modal size of core YDZ–3, which can be correlated to paleo-superlobe migration of the Huanghe River in the Holocene. Based on these observations, the presence of seven superlobes in the history are confirmed for the first time and their ages are well constrained in this study, including Paleo-Superlobes Lijin (6400–5280 yr BP), Huanghua (4480–4190 yr BP), Jugezhuang (3880–3660 yr BP), Shajinzi (3070–2870 yr BP), Nigu (2780–2360 yr BP), Qikou (2140–2000 yr BP), and Kenli (1940–1780 and 1700–1650 yr BP). By tuning geomorphological events to a sedimentary proxy derived from core YDZ–3 and comparing to various paleoenvironmental changes, we proposed that winter climate dominated Holocene shifts of the Huanghe River delta on millennial timescales, while summer monsoons controlled deltaic evolution on centennial timescales.
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