Collaborative Research: Reconstructing Pacific Trade Wind Variability - Extending and Replicating a Promising New Coral Proxy

尽管大气中的温室气体持续增加，但全球表面变暖在2000至2014年间明显放缓。气候模型和观测结果都表明，气候变暖的减缓或“中断”可能(至少部分是)归因于热带太平洋的强劲信风。这些强风将热量输送到次表层海洋，使大气变暖的热量减少。由于风的强度在十到十年的时间尺度上变化(与太平洋的自然变化有关)，过去100年来其他加速和减缓变暖的时期很可能与热带信风的这些变化有关。因此，未来十年，当周期逆转，信风再次减弱时，全球变暖可能会加速(S)。然而，到目前为止，我们对全球气温和热带太平洋风强度之间的联系的理解一直受到历史上风观测的匮乏的限制。该项目将利用从活珊瑚和化石珊瑚骨架中捕捉到的热带太平洋风变化的化学指纹，研究过去一个世纪和前工业化时代的风的变异性--及其与全球气温的联系。这项研究还将扩展这一新型WIND档案的应用，为将这种记录扩展到更多的地点和时间段提供关键的基础。这些关于最近过去热带太平洋风强度的自然档案有可能极大地提高我们对风的可变性对全球气候变化率的影响的理解。该项目还将通过支持两名职业生涯早期的女科学家、一名少数族裔博士后研究员和两名本科生，帮助扩大科学的参与度和多样性，她们将共同制定计划，促进波士顿大学的种族、性别和LGBTQ多样性、公平性和包容性。热带太平洋珊瑚记录极大地提高了我们对过去千年以来海洋对气候强迫变化的反应的了解，但我们对相关大气反应的理解仍然受到(往往是间接和/或远程的)水文学指标解释中的不确定性的限制。该项目利用现有的现代珊瑚和化石珊瑚核心以及一种前景看好的新珊瑚替代物来研究热带太平洋信风在自然和人为强迫变化中的可变性。在塔拉瓦环礁西风异常和珊瑚骨骼锰/钙之间联系的开创性研究的基础上，该项目将在不同地点(塔拉瓦、基里蒂马蒂、布塔里塔里和帕尔米拉)和不同时期(20世纪和小冰期/工业化前)校准和扩展这一新指标。初步结果表明，来自Kiritimati和Butaritari的珊瑚Mn/Ca捕捉了1997/98年厄尔尼诺事件期间在这些地点观测到的西风，支持了风变异性与环礁珊瑚Mn/Ca之间的因果联系，从而有可能在空间和时间上扩展基于Mn/Ca的信风重建。该项目将利用来自赤道太平洋西部和中部的重叠的现代珊瑚和化石，首次制作跨越20世纪和小冰期(LIA)至前工业化时期(1400-1850年)的太平洋信风强度的强劲、良好复制和定量重建。该项目还通过探索这种新的替代物的优点和局限性，为基于珊瑚锰/钙的信风重建扩展到其他地点和时间段奠定了基础。这样的信风重建有可能极大地提高我们对信风可变性及其对全球气候变化的影响的理解，以应对自然和人为的强迫。

Global surface warming markedly slowed between 2000 and 2014 despite a continued increase in greenhouse gases in the atmosphere. Both climate models and observations suggest that this slowdown or "hiatus" in warming may be attributed (at least in part) to strong trade-winds in the tropical Pacific. These strong winds transport heat into the subsurface ocean, leaving less heat to warm the atmosphere. Because wind strength changes on a decade-to-decade timescale (associated with natural variability in the Pacific), other periods of both accelerated and reduced warming over the last 100 years are likely tied to these changes in tropical trade-winds. Thus, warming will likely accelerate in the coming decade(s) when the cycle reverses and trade-winds weaken once again. However, our understanding of the link between global air temperatures and tropical Pacific wind strength to date has been limited by the scarcity of historical wind observations. This project will utilize the chemical fingerprints of changes in tropical Pacific winds captured in the skeleton of living and fossil corals to investigate past wind variability - and its link to global air temperatures - across the past century and preindustrial era. The research will also extend the application of this novel wind archive, providing key groundwork for such records to be extended to additional sites and time periods. These natural archives of tropical Pacific wind strength over the recent past have the potential to dramatically improve our understanding of the impact of wind variability on the rate of global climate change. This project will also contribute to broadening participation and diversity in science by supporting two early career female scientists, a minority postdoctoral researcher and two undergraduates, who will together develop programs to promote race, gender, and LGBTQ diversity, equity and inclusion at Boston University. Tropical Pacific coral records have dramatically improved our understanding of the oceanic response to changes in climate forcing over the past millennium, but our understanding of the associated atmospheric response remains limited by uncertainties in the interpretation of (often indirect and/or remote) hydrological proxies. This project leverages existing modern and fossil coral cores and a promising new coral proxy to investigate tropical Pacific trade wind variability across changes in natural and anthropogenic forcing. Building off pioneering studies linking westerly wind anomalies and coral skeletal Mn/Ca at Tarawa Atoll, the project will calibrate and extend this new proxy across sites (Tarawa, Kiritimati, Butaritari, and Palmyra) and time periods (20th century and Little Ice Age/preindustrial). Initial results demonstrate that coral Mn/Ca from Kiritimati and Butaritari capture the westerly winds observed at these sites during the 1997/98 El Niño event, supporting the causal link between wind variability and coral Mn/Ca at atolls with west-facing lagoons, and thus the potential for extending Mn/Ca-based trade-wind reconstructions across space and time. This project will produce the first robust, well-replicated, and quantitative reconstructions of Pacific trade wind strength spanning the 20th century and Little Ice Age (LIA) to preindustrial period (1400-1850CE) using overlapping modern and fossil corals from the western and central equatorial Pacific. This project also lays the foundation for coral Mn/Ca-based trade-wind reconstructions to be expanded to other sites and time periods by exploring the strengths and limitations of this novel proxy. Such trade-wind reconstructions have the potential to dramatically improve our understanding of trade-wind variability and its impact on global climate change in response to both natural and anthropogenic forcings.