Rainfall variability over northeastern Australia derived from coral luminescence data

Twenty coral cores from the Australian Institute of Marine Science's archive of long Porites spp. coral cores from the Great Barrier Reef were chosen for this study. The cores selected were from sites extending along much of the length of the Great Barrier Reef (between 11°-23°S); were located in nearshore waters, which would be affected by freshwater flood plumes (between 0 and 30km from the mainland) and previous analyses of annual coral growth records for these cores indicated that records started prior to 20th century. The cores were collected from reefs offshore from Red Wallis Is, Pascoe River, Jeannie River, Conical Rocks, Normanby Island, Dunk Island, Coombe Island, Brooke Island, Great Palm Island, Pandora Reef, Havannah Island, Archeron Island, Magnetic Island, Hook Island, Stonehaven Beach, North Molle Island, Cid Harbour, South Molle Island, Lupton Island and Humpy Island.Luminescence (excitation k (nm)/emission k (nm) = 390/490) was measured on slices from each core at 0.25 mm intervals with a 2 mm diameter beam using optical luminometry along a major growth axis of each coral core slice.Monthly instrumental rainfall for northeast Queensland including the catchments of rivers draining into the Great Barrier Reef was sourced from the Australian Bureau of Meteorology for the period 1900-2008. These data were used to calculate annual summer rainfall (October-March) for 1901 to 2008.17 of the annual coral luminescence series were significantly correlated with the instrumental rainfall record. These 17 series were used to develop a suite of reconstructions of Queensland rainfall (using PCA and linear regression analyses) - using between 17 and a single coral core. The reconstructions differ in the start year (depending on available coral records). All reconstructions were significantly calibrated and verified against the instrumental climate record.The longest reconstruction based on 3 coral records starts in 1685 and triples the length of the instrumental record. The single core reconstruction starts in 1639 but the 3-coral reconstruction is considered more robust. The purpose of the present study is to develop new reconstructions of NE tropical Queensland rainfall based on quantitative measurements of luminescence intensity using fluorescence spectroscopy in multiple coral cores from the Great Barrier Reef.

本研究选取了澳大利亚海洋科学研究所（Australian Institute of Marine Science）保存的、采自大堡礁的长身滨珊瑚属（Porites spp.）珊瑚岩芯共计20根。所选岩芯的采样点沿大堡礁大部分海域分布（南纬11°至23°之间），均位于距大陆0至30公里的近岸海域，易受淡水洪水羽流影响；且前期对这些岩芯的年度珊瑚生长记录分析显示，其记录起始时间早于20世纪。这些岩芯采自以下礁体沿岸：雷德沃利斯岛（Red Wallis Is）、帕斯科河（Pascoe River）、珍妮河（Jeannie River）、锥形礁（Conical Rocks）、诺曼比岛（Normanby Island）、邓克岛（Dunk Island）、库姆岛（Coombe Island）、布鲁克岛（Brooke Island）、大棕榈岛（Great Palm Island）、潘多拉礁（Pandora Reef）、哈瓦那岛（Havannah Island）、阿彻隆岛（Archeron Island）、磁岛（Magnetic Island）、胡克岛（Hook Island）、斯通黑文海滩（Stonehaven Beach）、北莫尔岛（North Molle Island）、西德港（Cid Harbour）、南莫尔岛（South Molle Island）、勒普顿岛（Lupton Island）以及汉皮岛（Humpy Island）。
研究人员采用光学光度法，沿每片珊瑚岩芯切片的主要生长轴，以2毫米直径的光束、0.25毫米的间隔，对每根岩芯的切片进行发光强度测定，激发波长/发射波长为390纳米/490纳米。
1900年至2008年期间，昆士兰州东北部（包括注入大堡礁的河流流域）的月度仪器观测降水数据源自澳大利亚气象局（Australian Bureau of Meteorology）。基于这些数据，研究人员计算得到1901年至2008年的年度夏季（10月至次年3月）降水量。
17组年度珊瑚发光序列与仪器观测降水记录呈显著相关。研究人员以这17组序列为基础，采用主成分分析（Principal Component Analysis，PCA）和线性回归分析方法，构建了一系列昆士兰州降水重建序列——所用珊瑚岩芯数量从17根缩减至单根。这些重建序列的起始年份取决于可用的珊瑚记录时长，且所有重建序列均通过了仪器气候记录的显著校准与验证。
基于3根珊瑚岩芯的最长重建序列起始于1685年，将仪器记录的时长增至三倍；单根岩芯的重建序列起始于1639年，但学界普遍认为基于3根岩芯的重建结果更为稳健。本研究的核心目标是，依托大堡礁多根珊瑚岩芯的荧光光谱法定量测定的发光强度数据，构建昆士兰州东北部热带区域降水的新型重建序列。