珊瑚微环礁记录的西沙群岛近百年来海平面的年际变化

Under the influence of global change，the sea-level rise has become a major global issue which is widely concerned by the international society. By studying the sea-level annual fluctuations from Porites microatolls during the past one hundred years, it will be conducive to extending the time sequence of device-measured sea-level records, revealing the patterns of sea-level fluctuations, and predicting the long-term trend of sea-level fluctuations under climate change. On the other hand, it will also be helpful to further probe the high-resolution sea- level recording function of microatolls in the Xisha Islands, and which can be used to explore longer time scale sea-level history. Porites microatolls have long been regarded as a perfect carrier to record the sea-level fluctuations with high resolution. However, so far, nobody has ever done such research on the sea-level recording function of modern microatolls in Xisha Islands yet. This research will focus on porites microatolls of Yongle Atoll, Xisha Islands. Based on field survey of microatolls, we’ll make X-ray photographic analysis of skeleton samples of Porites microatolls been collected, build accurate chronological framework using growth bands and U-series dating methods. Then, we’ll reconstruct the sea-level history for the past one hundred years by making in-situ field monitoring and growth bands lab analysis of microatolls. Also, high-resolution sequence of annual sea surface temperature (SST) fluctuations should be built by measuring Sr/Ca ratio of Porites skeleton samples, and the fitting relations between SST and sea-level fluctuations will be worked out, which is essential to explore the driving mechanism of sea-level fluctuations over the past century.

全球变化背景下的海平面上升是目前国际社会关注的重大问题。研究滨珊瑚微环礁记录的近百年来海平面年际变化历史，一方面有助于延长器测海平面记录的时间序列，揭示海平面变化规律，预测在气候变化背景下的海平面变化趋势；另一方面，将进一步阐明西沙微环礁高分辨率的海平面记录功能，服务于更长时间序列历史海平面的研究。滨珊瑚微环礁一直被认为是高分辨率地记录过去海平面变化的绝佳载体, 但现代微环礁的海平面记录功能在西沙的研究还是空白。本项目拟选择西沙群岛永乐环礁的滨珊瑚微环礁，以微环礁野外调查为基础，对采集到的滨珊瑚微环礁骨骼样品开展 X光照相分析，依据生长年纹层和U系定年建立准确的年代框架；通过现场对微环礁的原位监测和室内微环礁年纹层的分析，重建西沙海域近百年来海平面的年际波动历史；通过对滨珊瑚骨骼的Sr/Ca值测定建立年分辨率的海温变化序列，分析SST和海平面波动的拟合关系，揭示百年来海平面波动的驱动机制。

珊瑚微环礁长期以来一直被用作过去海平面的精确指示器，可以提供十年至千年尺度的高分辨率年际海平面变化记录。研究课题在国内外首次以西沙群岛永乐环礁滨珊瑚微环礁为载体，采用现场全站仪观测、珊瑚骨骼X光成像分析和高精度U系测年等技术，重建了过去近百年西沙海域海平面年际变化历史及其空间差异性，研究成果弥补了西沙海域过去百余年来高分辨海平面变化器测记录严重不足，证实了过去五十年来南海和全球其他海区一样都面临着海平面快速上升的威胁，为更长尺度的海平面重建以及预估未来相对海平面变化提供了有利的数据和参考；同时，利用微环礁珊瑚骨骼Sr/Ca和现代器测数据，建立了西沙海区的古海表温度（SST）序列，探讨了过去十年-百年尺度SST和海平面变化的联系和驱动机制，发现活体微环礁骨骼Sr/Ca变化与仪器海表温度(SST)记录具有很强的相关性，微环礁骨骼可以保存大量与厄尔尼诺-南方涛动 (ENSO)相关的海表温度SST变化及其引起的海平面变化信息。