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Abstract: The sources and burial patterns of organic matter in Shamei Lagoon, Hainan, China, were investigated by analyzing the collected sediment cores, in terms of the variations in total organic carbon (TOC), total nitrogen (TN), stable carbon isotopic composition (δ13C and δ15N), and the ratio of total organic carbon to total nitrogen (TOC/TN). On such a basis, the environmental evolution and primary productivity changes of the lagoon were revealed, and the impacts of both natural environmental changes and human activities were identified. Downcore variation patterns of the parameters representing sources and burial flux of organic matter were predominantly related to natural evolution of the lagoon from 1800 to 1950 and they were increasingly affected by human activities afterwards. In the period 1800–1900, the water exchange capacity of the lagoon declined substantially, but it was still suitable for the growth of marine phytoplankton, as is indicated by relatively high proportion and burial flux of organic matter originated from marine sources. During 1900–1950, the lagoon was transformed into a freshwater environment. After 1950, due to strong influence by human activities, the local freshwater phytoplankton became the major source of buried organic matter; at the same time, marine lost its niche and its burial flux was much lower than that of its freshwater counterpart. The large increment of buried freshwater organic matter also indirectly reflects the eutrophication trend since 1950. [Copyright &y& Elsevier]

This study analyzed the characteristics and the bearing capacity of water surge disasters in Boao Bay, a typical estuarine lagoon. The Danish Hydraulic Institute's (DHI's) MIKE 21 modeling suite was used to numerically simulate the water surges from flood, storm, and combined flood and storm processes. The results show that, in Boao Bay, the peak water surge level caused by the combination of flooding and storm surges is very similar to the level caused by flooding or storm surges alone. Additionally, the storm surge bearing capacity is much greater than the flood bearing capacity. When there is only one entrance, the bay's flood bearing capacity increases with the entrance width, but when the entrance width exceeds 550 m, the flood bearing capacity stabilizes rapidly. However, opening an additional entrance to the south can further increase the flood bearing capacity. Based on hydrometeorological forecasts, this study suggests that the risk of water surge disasters can be reduced by proactively modifying the shape of the entrance. [ABSTRACT FROM AUTHOR]

There are concerns that intense tropical cyclones (TCs) are expected to become more frequent and powerful in warming climates. However, the long-term trend of TC activities, the spatiotemporal variability of such trends across different latitudes of the Western North Pacific (WNP), and the drives of the variability remain unclear. Here, we present a reconstruction of a 1600-year paleo-TCs activity using a sediment core taken in Li'an Lagoon located in southeastern Hainan Island, South China Sea. We used muti-dating methods (210Pb and AMS 14C dating) for age control and muti-proxy analysis (XRF geochemical element scanning and grain size analysis) for identifying periods of frequent intense TC activities. Based on an updated compilation of basin-wide paleo-TC records, we confirm that there exists a seesaw pattern of intense TC frequency between low and middle latitude in the WNP. Comparing with global and regional paleoclimate proxies, we propose that the basin-wide latitudinal TC activity variation in the WNP can be linked to the migration of Western Pacific Subtropical High (WPSH) and its associated high-latitude forcings (e.g., NAO) and low-latitude internal variability forcings (i.e., El Niño Southern Oscillation, sea surface temperature (SST)). More intense TC will occur at low latitudes in the future, though with less frequency. • A 1600 years high-resolution paleo-TCs records are reconstructed. • A clearly seesaw pattern were identified between TC activity at low and middle latitude over the WNP were found. • WPSH play an intermediate regulation role in controlling the TC latitudinal shift. [ABSTRACT FROM AUTHOR]

Understanding long-term, large cyclone activity is critical for coastal management and disaster prevention and mitigation, particularly with projected rising sea level and increasing cyclone frequency and the intensity. Here we present sedimentary evidence (cyclone overwash deposits, beachrock boulders, and cyclone-induced clastic deposits) of historic large cyclone events from coastal dune deposits on eastern Hainan Island, China. Based on luminescence dating and sedimentological analysis, eight historic tropical cyclone events (at 1095 ± 90 BCE, 900–1000 BCE, 975 ± 50 CE, 1720 ± 20 CE, 1740 ± 35 CE, 1790 ± 25 CE, 1850 ± 15 CE, and 1895 ± 10 CE) have been identified in this region. The elevation of the termination point of cyclone overwash deposit layers that represent the paleo-cyclone minimum wave run-up stage, in combination with knowledge of present-day cyclone events, was applied to assess the intensity of these extreme events. The intensity of these cyclone events was likely greater than that of cyclones in the local instrumental records. Furthermore, these large cyclone events correspond to historic records of devastating cyclones. Through comparison with regional and global climate records, we infer that the variability of large cyclones in the South China Sea was probably modulated by the El Niño-Southern Oscillation, western Pacific warm pool, and local sea surface temperatures over the past 3400 yr. These results provide an improved understanding of long-term, extreme cyclone events and their response to climate change, thereby contributing to regional planning and coastal defense strategies. [ABSTRACT FROM AUTHOR]

The link between tropical cyclone (TC) activity in the South China Sea (SCS) and global climate change is commonly debated and there is a clear need for long-term geological records of TC activity if we are to clarify this connection. Multi-millennial, high-resolution paleo-storm records from the SCS are rare in the region and this causes difficulties for those exploring potential climate drivers of TC variability over centennial to millennial timescales and reduces our ability to fully assess the risks associated with future TC activity. This paper presents an age-constrained, mud-dominated sedimentary sequence from a coastal lagoon on Hainan Island, China. Multiproxy analyses incorporating chronological, lithological, sedimentological, and geochemical evidence were used to infer storm deposits preserved within the sequence and to reconstruct a time series of storm activity in the SCS during the mid-to-late Holocene. This long sedimentary record shows that TCs were highly active over the periods 5500 to 3500 and 1700 to 0 cal yrs. BP, and these periods contrast with a relatively quiet period 3500–1700 cal yrs. BP. An apparent inverse correlation between TC reconstructions from the SCS and those from the Korean Peninsula and Japan implies an oscillating pattern across the SCS and western North Pacific (WNP) over centennial to millennial timescales. A comparison between the sedimentary and paleoclimatic records implies that the El Niño–Southern Oscillation was not the only mechanism responsible for typhoon variability over the past 7500 cal yrs. BP, suggesting that other factors such as the thermal state of the western Pacific warm pool likely also had a strong influence on both SCS and WNP TC variability. • Sedimentological evidence from Hainan Island was used to reconstruct typhoon activity in the SCS over the mid–late Holocene. • There exists a well-defined seesaw pattern in storm activity across the WNP basin during the study period. • Periods of increased (reduced) storm activity in the SCS typically coincide with La Niña (El Niño) periods and warm (cold) phases of the WPWP during the mid-late Holocene. [ABSTRACT FROM AUTHOR]