Paleo-Typhoon Events as Indicated by Coral Reef Boulder Deposits on the Southern Coast of Hainan Island, China

Liang Zhou,Shu Gao,Yang Yang,Changliang Tong,Aijun Wang,Jianjun Jia

doi:10.3389/fmars.2021.746773

Abstract

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.

Highlights

Intense tropical cyclones (TCs) are among the deadliest natural disasters for the populations inhabiting coastal areas
In the northwestern Pacific and South China Sea regions, modern observations and paleotempestological studies suggest that El NiñoSouthern Oscillation (ENSO) plays a significant role in typhoon longitudinal variations, with more movement routes directed toward Korea and Japan during El Niño times, but toward the northern South China Sea during La Niña times (Chan, 1985, 2005; Woodruff et al, 2009; Chen et al, 2012; Zhou et al, 2019a,b)
These results are consistent with local observations and with findings from other coastlines in the Asia–Pacific region that periodically experience direct hits by large typhoons

Summary

Introduction

Intense tropical cyclones (TCs) are among the deadliest natural disasters for the populations inhabiting coastal areas. Any significant change in the frequency and/or intensity of coastal TCs due to climate change is likely to have a notable impact on the economic prosperity of coastal areas. On the other hand, predicting the frequency and magnitude of large typhoons in the region in the background of global warming are relatively rare, especially for the northern coastlines of the South China Sea. The need for coastal risk assessment, raising societal awareness, and preparation to prevent the possible adverse impacts of large storm events are critical for East Asian coastal populations. Short meteorological records and incomplete historical documentation may lead to imprecision in the estimation of typhoon disaster risk (Suursaar et al, 2015)

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