关键词: 珊瑚生长率, SST, 工业革命, 西沙海域

Abstract:

The skeletal growth rate of Porites coral is an important indicator to reconstruct sea surface temperature (SST). This paper makes use of Porites lutea collected from Yongxing Island, Xisha Islands to construct a coral growth rate thermometer. Based on the thermometer, it reconstructed the SST time series of Xisha sea area since industrial revolution (1880-2007). The result shows that the mean SST was 27.27℃, ranging from 26.1 to 28.5℃ during the period from 1880 to 2007. From 1880 to 1892, SST declined with fluctuations to form a rapid cooling period and SST reached the lowest value of 26.1℃ in 1892. From 1893 to 1935, SST fluctuated all the time to form a platform of low SST. From 1936 to 1957, SST went up at first and then went down, which form a peak of wave. During the period from 1957 to 2003, SST increased rapidly in Xisha Waters. From 2003 to 2007, SST showed a decline trend in Xisha Waters. On the interdecadal time scale, quasi 60-years cycle of climate system might regulate SST change pattern in Xisha waters. At the interannual scale, the intensity of winter monsoon, volcanic activity and ENSO exerted influences on SST in Xisha waters together. In different period, the contribution of different drive factors was different, which lead to the complexity of SST change in Xisha Waters. After 1957 the global warming caused by human activities has become a major driving force of SST increase process in Xisha waters. The SST-fall period from 1880 to 1892 was driven by ENSO, volcanic activity and quasi 60-years cycle of climate system together. The lower winter monsoon velocity causing SST rise counteracted the SST decrease effect of volcanic activity and quasi 60-years cycle of climate system to form a platform of low SST from 1893 to 1935 finally. From 1936 to 1957, SST formed a peak of wave in Xisha Waters, which was driven by the natural variability of the climate system and lower winter monsoon velocity. During the period, the volcanic force resulted in the asymmetry of SST wave crest. During the period from 1957 to 2003, the human-induced greenhouse effects might become the main force to drive the SST increase rapidly in Xisha waters. The cooling process in Xisha waters from 2003 to 2007 might respond to the global warming trend slowdown, which was a result of the interactions between natural forcing and anthropogenic forcing. Anthropogenic forcing always drives SST increases in Xisha waters. Meanwhile, the natural variability of the climate system is in the turn period, the sunspot activity is relatively low, water vapor decreases in the stratosphere, the concentration of atmospheric aerosols increases in the troposphere and the Atlantic meridional overturning circulation accelerates, which drive the temperature reduction. It is obviously that the state is delicate. Once any factor of natural forcing weakens, the declined trend of SST in Xisha waters may be replaced by increase trend of SST again.

Key words: coral-growth rate, SST, industrial revolution, Xisha waters