Emergence of an anthropogenic salinity signal in the IndoPacific

印度洋和太平洋的温度变化对遥远的社会、生态系统和经济有着深远的影响。厄尔Niño南方涛动（ENSO）就是一个明显的例子。ENSO可以引起温度变化，从而促使全球天气发生巨大变化。它可以影响热浪、干旱、洪水和风暴。尽管印太地区意义重大，但目前尚不清楚该地区将如何应对不断上升的温室气体。气候模型一致认为，人为引起的气候变化将改变全球气温和降雨模式。然而，气候模型在这些变化的幅度甚至迹象上往往存在分歧。了解印太地区气候变化的另一个挑战是，内部变化可能掩盖趋势。来自热带海洋的长期记录对于解开这种不确定的反应至关重要，但很少有仪器存在。该项目开发了新的方法来评估印太数据稀少地区的气候变化。珊瑚数据可以提供有关过去温度和水文条件的信息。这个项目将综合几个世纪以来来自珊瑚、仪器观测和气候模型的数据。这些数据将用于重建气候变率。重建的温度、盐度和降水将与气候模式模拟结果进行比较。这项研究将加强对热带水文循环对气候变化响应的科学理解。最后，这项工作将支持一名早期职业科学家、一名研究生和一名本科生研究人员。本项目将在离线古气候数据同化（paleo-DA）框架下利用长期的、季节性分辨的热带珊瑚记录和仪器观测，评估热带印度洋-太平洋地区出现的人为信号。这项工作将利用新方法综合各种数据来源（古气候代用物、再分析产品、同位素支持模型、大集合、古da）来评估从18世纪至今的内部变率和温度、盐度和降水变率的变化范围。特别是，这项工作旨在填补一个关键的数据缺口，将海面盐度与珊瑚氧同位素记录（d18Ocoral）和珊瑚衍生的海水氧同位素组成（d18Osw）在季节到多年代际时间尺度上联系起来。该项目旨在严格量化与使用珊瑚d18O和珊瑚衍生d18Osw有关的不确定性，以检查历史水文气候变化，并建立最佳实践，以推断各种时间尺度下与海面盐度的关系。在珊瑚衍生的重建中，对与人为信号出现相关的时间、强度和空间模式的解释将与CMIP6大集合历史和人为强迫模拟进行对比。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Temperature changes in the Indian and Pacific Oceans have profound impacts on distant societies, ecosystems, and economies. The El Niño Southern Oscillation (ENSO) is a clear example. ENSO can cause temperature changes that prompt large shifts in global weather. It can influence heatwaves, droughts, floods, and storms. Despite the significance of the IndoPacific, it is still not clear how this region will respond to rising greenhouse gases. Climate models agree that human-caused climate change will alter global temperature and rainfall patterns. However, climate models often disagree on the magnitude and even the sign of those changes. Another challenge to understanding climate change in the IndoPacific is that internal variability can mask trends. Long records from the tropical oceans are essential to untangle this uncertain response, but few instrumental exist. This project develops new ways to evaluate climate change in the data-sparse regions of the IndoPacific. Coral data can provide information about past temperature and hydrological conditions. This project will synthesize centuries of data from corals, instrumental observations, and climate models. These data will be used to reconstruct climate variability. Reconstructions of temperature, salinity, and precipitation will be compared with climate model simulations. This research will bolster scientific understanding of the tropical hydrological cycle response to climate change. Finally, this work will support an early career scientist, a graduate student, and undergraduate researchers. This project will evaluate the emergence of an anthropogenic signal in the tropical IndoPacific by leveraging long, seasonally-resolved tropical coral records with instrumental observations in an offline paleoclimate data assimilation (paleo-DA) framework. The proposed work will utilize novel methods to synthesize diverse sources of data (paleoclimate proxies, reanalysis products, isotope-enabled models, large ensembles, paleo-DA) to evaluate the range of internal variability and changes in temperatures, salinity, and precipitation variability from the 18th-century to the present. In particular, this work seeks to fill a critical data gap linking sea surface salinity to coral oxygen isotopic records (d18Ocoral) and coral-derived reconstructions of the oxygen isotopic composition of seawater (d18Osw) at seasonal to multidecadal timescales. This project aims to rigorously quantify uncertainties related to using coral d18O and coral-derived d18Osw to examine historic hydroclimate change and to establish best practices for inferring relationships with sea surface salinity at a variety of timescales. Interpretation of the timing, magnitude, and spatial patterns associated emergence of an anthropogenic signal in the coral-derived reconstructions will be contrasted with CMIP6 Large Ensemble historical and anthropogenically forced simulations.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.