Coastal dune sediments and landforms offer a unique opportunity to understand climate change and sea level change on the centennial-millennial time scale. However, there is a paucity of chronological studies on the effects of storms on the evolution of coastal dunes along the temperate coastline of China. In this study, optically stimulated luminescence (OSL) dating of sand dunes was conducted to investigate the process and mechanism of coastal dune evolution on the southeastern coast of Hainan Island, China. The results show that the coastal dune evolution experienced three rapid accumulation periods: 28-21 ka, 14-4 ka, and 3.0 ka-present. The three rapid accumulation periods correspond to the last glacial maximum, the late Pleistocene/early-mid Holocene, and the late Holocene climatic dry-cold period, respectively. Sea level change and the East Asian winter monsoon, in conjunction with the enhanced storminess, play a key role in driving the sand dune evolution on the south-eastern coast of Hainan Island. These findings are of great significance for regional planning and coastal defense schemes.

The southern coast of Hainan Island, China, is one of the most frequently hit areas of tropical cyclones in the Northwest Pacific regions. Although some of the extreme typhoon events were known in historical times, quantitative information on the timing and magnitude of paleo-typhoon events in this coastal area remains rare. In the present study, a large number of coral reef boulders were found on the Xiaodonghai reef platform, on the south coast of Hainan Island. Morphometric analysis of the boulders shows an exponentially fining landward trend, indicating a storm origin; a wave-induced current velocity of 2.41–5.71 m/s during the storm events is required to transport the boulders that were originally situated outside the reef edge. Based on the U/Th and 14C dating for the age-indicating samples taken from the boulders, seven major periods with intense typhoon activities were identified for the last 4,000 years, i.e., 1800–1500 BCE, 1200–900 BCE, 50–120 CE, 550–800 CE, 900–1000 CE, 1350–1900 CE, and 1910–2000 CE. A comparison with the regional typhoon records in terms of climatic parameters in the northwestern Pacific and the South China Sea regions indicates that the longitudinal variations of intense typhoon frequency were mainly controlled by El Niño-Southern Oscillation (ENSO), dominantly modulated by the Intertropical Convergence Zone. Because of the future warming climate, there will be a trend of enhanced typhoon risk for the southern Hainan Island coasts.

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Marine sediment deposits near the Qiongzhou Strait have great potential as sources for beach nourishment and infrastructure industry aggregates. Estimation of bedload transport during the spring tide improves the understanding of the sediment movement characteristic under dynamic conditions, which would further favor the assessment and mining of marine sand resources. To study the bedload transport at the eastern entrance of the Qiongzhou Strait, the surficial sediment distributions were obtained through hundreds of sediment samples from field work. A semi-implicit cross-scale hydrological science integrated system model was adopted and validated to simulate the tidal currents in the Qiongzhou Strait. With field observation and simulated data, we estimated the spring tide bedload transport in the study area using the Bagnold Model. The transport rate in the study area was found to have large temporal and spatial variation. The net transport direction during the spring tide cycle was eastward in the southern parts of the strait and westward in the northern strait. Our research has important implications for regional engineering and marine resources management.