Abstract
Abstract. To constrain models on global sea-level change regional proxy data on coastal change are indispensable. Here, we reconstruct the Holocene sea-level history of the northernmost China Sea shelf. This region is of great interest owing to its apparent far-field position during the late Quaternary, its broad shelf and its enormous sediment load supplied by the Yellow River. This study generated 25 sea-level index points for the central Bohai coastal plain through the study of 15 sediment cores and their sedimentary facies, foraminiferal assemblages and radiocarbon dating the basal peat. The observational data were compared with sea-level predictions obtained from global glacio-isostatic adjustment (GIA) models and with published sea-level data from Sunda shelf, Tahiti and Barbados. Our observational data indicate a phase of rapid sea-level rise from c. −17 to −4 m between c. 10 and 5 ka with a peak rise of 6.4 mm a−1 during 8.7 to 7.5 ka and slower rise of 1.9 mm a−1 during 7.5 to 5.3 ka followed by a phase of slow rise from 5 to 2 ka (∼0.4 mm a−1 from −3.58 m at 5.3 ka cal BP to −2.15 m at 2.3 ka cal BP). The comparison with the sea-level predictions for the study area and the published sea-level data is insightful: in the early Holocene, Bohai Bay's sea-level rise is dominated by a combination of the eustatic and the water load components causing the levering of the broad shelf. In the mid to late Holocene the rise is dominated by a combination of tectonic subsidence and fluvial sediment load, which masks the mid-Holocene highstand recorded elsewhere in the region.
Highlights
The sea-level rise since the mid-19th century is one of the major challenges to humanity of the 21st century (IPCC, 2014)
The driving mechanisms of this rise are relatively well-known on a global scale, but on a regional scale the mechanisms are modified by regional Holocene sea-level history, This history is a background signal controlled by ice load and the corresponding response of the deformable Earth (Clark et al, 1978) and, in addition, by regional parameters such as fluvial sediment supply and shelf geometry
A several-metre sea-level highstand is predicted for the East China Sea coast during the mid-Holocene (Bradley et al, 2016), but this high highstand seems to be an overestimate when compared to observational data (Bradley et al, 2016) which indicate a minor Holocene highstand for the East China Sea coast (Zong, 2004) and no obvious Holocene highstand for delta area of Yangtze River (Xiong et al, 2020) and the Pearl River delta (Xiong et al, 2018)
Summary
The sea-level rise since the mid-19th century is one of the major challenges to humanity of the 21st century (IPCC, 2014). A several-metre sea-level highstand is predicted for the East China Sea coast during the mid-Holocene (Bradley et al, 2016), but this high highstand seems to be an overestimate when compared to observational data (Bradley et al, 2016) which indicate a minor Holocene highstand for the East China Sea coast (Zong, 2004) and no obvious Holocene highstand for delta area of Yangtze River (Xiong et al, 2020) and the Pearl River delta (Xiong et al, 2018) From this the question arises whether the observational data are inaccurate, whether the GIA model parameters are too poorly constrained and how fluvial sediment supply influences the sea-level history
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