Upwelling and bleaching on the Great Barrier Reef (MTSRF Project 2.5i.2)

As part of MTSRF Task 2.5i.2, a range of indices were investigated to quantify upwelling on the central Great Barrier Reef (GBR), Australia. These indices are necessary for exploring environmental and biological relationships in areas where upwelling may be sporadic and less intense, especially along western boundary currents such as the East Australian Current. 'Upwelling days' (the number of days of upwelling, inferred from erratic downward temperature spikes) and diurnal variation in subsurface temperature (max-min, 20m depth) were found to be the best metrics to describe the duration and intensity of upwelling events, respectively. These were used to examine key characteristics of shelf-break upwelling in the central GBR. Temperature logger data (20m) were used to derive 'upwelling days' and the local mean summer temperatures (Dec - Feb) and NOAA AVHRR Pathfinder data were used to derive regional SSTs. To investigate the best metrics to quantify upwelling and to explore relationships between these metrics, SST and coral bleaching. Exploration of upwelling indices was done using hierarchical classification trees. Linear regression analysis was used to explore relationships between upwelling and SST and coral bleaching events, especially 1998 and 2002.Coordinates of the temperature logger sites are:Magnetic Island (Florence Bay): LATITUDE -19.12248, LONGITUDE 146.88155Kelso Reef: LATITUDE -18.44701, LONGITUDE 146.98907Myrmidon Reef: LATITUDE -18.25673, LONGITUDE 147.38104

作为MTSRF任务2.5i.2的组成部分，研究团队针对澳大利亚中部大堡礁（Great Barrier Reef，GBR）的上升流量化问题，开展了一系列指数指标的构建与评估工作。这些指数可用于探究上升流偶发且强度较弱海域的环境与生物关联机制，尤其适用于东澳海流（East Australian Current）这类西边界流流经区域。
研究发现，“上升流天数”（指通过不规则降温峰值推断得到的上升流累计日数）与20米深度次表层温度的日变化幅度（即最大值与最小值之差），分别为描述上升流事件持续时长与强度的最优量化指标。上述两项指标被用于解析中部大堡礁陆架坡折带上升流的关键特征。
20米深度的温度记录仪数据被用于计算“上升流天数”与局地夏季平均水温（12月至次年2月）；美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration，NOAA）的AVHRR Pathfinder数据集则被用于推算区域海表温度（Sea Surface Temperature，SST）。
为筛选最优上升流量化指标，并探究该类指标、海表温度与珊瑚白化事件之间的关联，研究采用层级分类树算法完成了上升流指数的筛选工作；同时通过线性回归分析，探究了上升流与海表温度、珊瑚白化事件（尤其是1998年与2002年发生的白化事件）之间的关联机制。
温度记录仪布设点位的坐标信息如下：
磁岛（弗洛伦斯湾）：纬度-19.12248，经度146.88155
凯尔索礁（Kelso Reef）：纬度-18.44701，经度146.98907
米尔米顿礁（Myrmidon Reef）：纬度-18.25673，经度147.38104