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年全球温度的替代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。大部分来自高纬度树木年轮记录的数据表明，20世纪后期是上个千年最温暖的时期。然而，与这些估计相关的不确定性是显著的，特别是在大约700年前结束的中世纪变暖时期。地球上的温度变化？S表面与全球热带最接近，其中75%是海洋；然而，很少有来自低纬度海洋的跨越过去1000年的数据集。为了改善全球温度重建和减少不确定性，迫切需要低纬度海洋的海表温度（SST）的良好复制记录。大量长寿的珊瑚，像树木的年轮一样，在一年生带中积累碳酸钙骨架，有可能提供这些信息。最近，渔业指数利用珊瑚骨骼生长与水温之间的关系，应用了一种重建年海温的方法。在3种珊瑚的多种记录中，珊瑚生长在年际和更长时间尺度上捕获了仪器记录中50-60%的海温变率。将该方法应用于巴哈马约440年的慢生长珊瑚，表明海温在现代~ AD1550的误差范围内，小冰期海温比今天低约1ºC，并且在过去50年的海温中存在强烈的人为信号。PIs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海温的方法，并将其应用于低纬度大西洋和太平洋的多世纪代用海温记录。对完整珊瑚岩心进行三维CAT扫描的数据采集相对快速和廉价，可以从每个地点的多个珊瑚群落中产生许多不同长度的记录，并且使用树木年轮学中应用的技术，提供足够的数据来提供重建海温的实际误差估计。资金将支持3名pi，一名博士后研究科学家，一名博士生和一名本科生的研究经验。

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.