Resolving 20th Century Sea Surface Temperatures in the Central Equatorial Pacific with Laser Sr-U

太平洋中部表层海洋变暖影响了世界各地的天气模式。但我们目前对该地区过去的温度历史知之甚少，这影响了对未来天气的模型预测。该项目使用100年前热带珊瑚的骨骼来读取上个世纪的海洋温度。珊瑚骨骼的化学成分随着海洋温度的变化而变化，这些信息存储在生长带中，就像树上的年轮一样。激光被用来仔细采样珊瑚骨架，并在太平洋上的关键地点建立新的温度历史。有了这些新的记录，科学家们可以评估厄尔尼诺等大规模天气事件的规模和频率，并改进用于预测未来天气状况的气候模型。该项目支持本科生的研究经验和培训，以及伍兹霍尔海洋研究所博士后的早期职业指导。赤道太平洋的海洋表面温度(SSTs)对地球气候系统产生了巨大影响，但在卫星时代开始之前，赤道太平洋SSTs的观测记录，特别是用于定义厄尔尼诺-南方涛动(ENSO)的Nino 3.4区域，很少。因此，在19世纪末和20世纪的大部分时间里，ENSO的可变性和赤道太平洋海温的长期趋势很难受到约束，这对验证未来气候的模式预测具有重要意义。该项目试图利用珊瑚基锶铀温度计重建赤道中部太平洋(CEP)战略地点长达一个世纪的连续、每月分辨率的代理SST记录。开发和应用了一种新的激光消融方法，目标是连续的月间隔之间附着的骨架，以实现基于锶-铀的海温的月分辨率重建。在赤道太平洋西部、中部和东部收集的Porites珊瑚将产生新的月分辨记录，以(1)校准在22℃至32℃温度范围内月分辨sr-U与观测月分辨SST，以及(2)应用校准在Nino 3.4和Nino 4.0区域产生两个长达一个世纪的SST记录。这些站点的战略位置是为了捕捉20世纪CEP的SST趋势，20世纪ENSO事件的频率和幅度，以及这段时间内中太平洋与东太平洋厄尔尼诺的相对频率。新的数据集将有助于解决有关赤道太平洋平均状态和变率对人为强迫的反应的未决问题。此外，该项目将开发新的方法，从现代和化石珊瑚中生成准确的SST月度记录，并在这样做的过程中，转变热带太平洋气候的知识。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Warming of the surface ocean in the central Pacific affects weather patterns all over the world. But we currently know little about the past temperature history of this region which affects model projections of future weather. This project uses skeletons of 100-year old tropical corals to read ocean temperatures for the last century. The chemistry of coral skeletons changes when the ocean temperature changes and this information is stored in growth bands, much like rings in a tree. Lasers are used to carefully sample the coral skeleton and build new temperature histories at key locations across the Pacific Ocean. With these new records scientists can evaluate the size and frequency of large-scale weather events like El Niño and improve climate models used to predict future weather conditions. This project supports research experiences and training for undergraduate students as well as early career mentoring for a postdoctoral student at Woods Hole Oceanographic Institute.Sea surface temperatures (SSTs) of the equatorial Pacific exert an outsize influence on Earth’s climate system yet the observational record of equatorial Pacific SSTs, in particular the Nino 3.4 region that is used to define El Nino-Southern Oscillation (ENSO), is sparse prior to the start of the satellite era. Consequently, ENSO variability and the secular trend in equatorial Pacific SSTs are poorly constrained over much of the late 19th and 20th centuries with important implications for validating model projections of future climate. This project seeks to reconstruct century long, continuous, monthly resolved records of proxy SST from strategic locations in the central equatorial Pacific (CEP) using the coral-based Sr-U thermometer. A new laser ablation method is developed and applied, targeting skeleton accreted between successive monthly dissepiments, to enable Sr-U based SST reconstruction with monthly resolution. New monthly-resolved records from Porites coral collected in the western, central, and eastern equatorial Pacific will be generated to (1) calibrate monthly-resolved Sr-U versus observed monthly-resolved SST over a temperature range of 22 deg to 32 deg C and (2) apply the calibration to generate two century-long SST records at sites in the Nino 3.4 and Nino 4.0 regions. These sites are strategically located to capture the 20th century SST trend in the CEP, the frequency and amplitude of ENSO events over the 20th century, and the relative frequency of central versus east Pacific El Niño over this time period. The new datasets will help to resolve outstanding questions regarding the response of the equatorial Pacific mean state and variability to anthropogenic forcing. Additionally, the project will develop new methods for generating accurate monthly records of SST from modern and fossil corals and, in doing so, transform knowledge of the climate of the tropical Pacific.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.