Collaborative Research:Extracting Multi-century Low-latitude Sea Surface Temperatures from Coral Skeletons Using Replicated Records of Annual Growth: Method Refinement&Application

过去1000年全球气温的代用重建为理解最近的变暖趋势提供了一个背景，并允许更好地估计人为（温室气体）强迫对全球气候变化的贡献。主要由高纬度树木年轮记录汇编的数据表明，世纪后期是上个千年中最温暖的时期。然而，与这些估计相关的不确定性很大，特别是在700年前结束的中世纪变暖期间。地球温度的变化？地球表面最接近全球热带，其中75%是海洋，但很少有数据集，跨越过去1000年存在的低纬度海洋。为了改善全球温度重建并减少不确定性，迫切需要低纬度海洋的海表温度（SST）记录。大量长寿的珊瑚，在像树木年轮一样的年轮中增加碳酸钙骨架，有可能提供这一信息。研究所最近采用了一种重建年度SST的方法，该方法利用了珊瑚骨骼生长与水温之间的关系。在从3种珊瑚产生的多个记录中，珊瑚生长捕获了仪器记录中50-60%的SST变异，在年际和更长的时间尺度上。将该方法应用于从巴哈马收集的约440年长的缓慢生长的珊瑚表明，SST在现代~ AD 1550的误差范围内，小冰期SST比今天冷约1ºC，并且在过去50年的SST中存在强烈的人为信号。PI将在这一初步工作的基础上，重点改进从珊瑚生长记录中提取SST的方法，并将其应用于生成低纬度大西洋和太平洋的多世纪替代SST记录。通过对完整珊瑚核心进行3-D CAT扫描来获取数据相对快速且廉价，能够从每个地点的多个群落中生成许多不同长度的记录，并且使用树木年代学中应用的技术，提供足够的数据来提供重建SST的现实误差估计。资金将支持3个PI，博士后研究科学家，博士生和本科生的研究经验。

Proxy reconstructions of global temperatures over the past 1000 years provide a context for understanding recent warming trends and allow better estimates of the contribution of anthropogenic (greenhouse gas) forcing to global climate change. Data compiled mostly from high latitude tree ring records suggest that the late 20th century was the warmest period of the last millennium. Nevertheless, the uncertainties associated with these estimates are significant, especially during the period known as the Medieval Warming which ended ~700 years ago. Temperature changes at the earth?s surface follow most closely those of the global tropics, which are 75% ocean; yet few datasets that span the last 1000 years exist from the low latitude oceans. In order to improve global temperature reconstructions and to reduce uncertainties, well-replicated records of sea surface temperature (SST) from the low-latitude oceans are urgently needed. Massive long-lived corals, which accrete calcium carbonate skeleton in annual bands like growth rings on a tree, have the potential to provide this information. The PIs have recently applied a method of reconstructing annual SST that takes advantage of the demonstrated relationship between the skeletal growth of corals and water temperature. In multiple records generated from 3 coral species, coral growth captures between 50-60% of the SST variability in the instrumental record, on interannual and longer timescales. Applying the method to a ~440-year long slow-growing coral collected from the Bahamas suggests that SSTs were within error of modern ~ AD1550, that Little Ice Age SSTs were about 1ºC cooler than today and that there is a strong anthropogenic signal in the SSTs of the last 50 years. The PIs will build on this initial work, focusing on refining the method of extracting SST from coral growth records and applying it to generate multi-century long proxy SST records for the low-latitude Atlantic and Pacific Oceans. Data acquisition by 3-D CAT scanning of intact coral cores is relatively rapid and inexpensive, enabling generation of many records of varying lengths from multiple colonies at each site, and, using techniques applied in dendrochronology, provide enough data to provide realistic error estimates on reconstructed SSTs. Funding will support 3 PIs, a post-doctoral research scientist, a PhD student, and research experience for an undergraduate.