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

2000年至2014年间，尽管大气中温室气体持续增加，但全球地表变暖明显放缓。气候模式和观测都表明，这种变暖的减缓或“中断”可能归因于（至少部分地）热带太平洋的强劲信风。这些强风将热量输送到地下海洋，留下更少的热量来温暖大气。由于风强度的变化是以十年为单位的时间尺度（与太平洋的自然变率有关），因此在过去100年里，其他加速或减缓变暖的时期很可能与热带信风的这些变化有关。因此，在未来十年，当周期逆转，信风再次减弱时，变暖可能会加速。然而，迄今为止，我们对全球气温和热带太平洋风强度之间联系的理解受到历史风观测的缺乏的限制。该项目将利用从活珊瑚骨架和化石珊瑚中捕获的热带太平洋风变化的化学指纹，调查过去一个世纪和前工业化时代的风变化及其与全球气温的关系。这项研究还将扩展这种新型风档案的应用，为这种记录扩展到其他地点和时间段提供关键的基础。这些热带太平洋风强度的自然档案在最近的过去有可能极大地提高我们对风变率对全球气候变化速度的影响的理解。该项目还将通过支持两名早期职业女性科学家、一名少数族裔博士后研究员和两名本科生，为扩大科学的参与度和多样性做出贡献，她们将共同制定项目，促进波士顿大学种族、性别和LGBTQ的多样性、公平和包容。热带太平洋珊瑚记录极大地提高了我们对过去一千年中海洋对气候强迫变化的响应的理解，但我们对相关大气响应的理解仍然受到（通常是间接和/或远程）水文代用物解释中的不确定性的限制。该项目利用现有的现代和化石珊瑚岩芯以及一种有前景的新珊瑚代理来研究热带太平洋信风在自然和人为强迫变化中的变异性。在塔拉瓦环礁将西风异常与珊瑚骨架Mn/Ca联系起来的开创性研究的基础上，该项目将在不同地点（塔拉瓦、基里蒂玛蒂、布塔里塔里和帕尔米拉）和不同时期（20世纪和小冰河期/工业化前）校准和扩展这一新的替代指标。初步结果表明，Kiritimati和Butaritari的珊瑚Mn/Ca捕获了1997/98年El Niño事件期间在这些地点观测到的西风，这支持了风变率与环礁西向泻湖珊瑚Mn/Ca之间的因果关系，因此有可能将基于Mn/Ca的信风重建扩展到时空上。该项目将利用赤道太平洋西部和中部的现代珊瑚和化石珊瑚的重叠，对20世纪和小冰期（LIA）至工业化前时期（公元1400-1850年）的太平洋信风强度进行首次可靠的、复制良好的定量重建。该项目还为珊瑚Mn/ ca信风重建奠定了基础，通过探索这种新代理的优势和局限性，将其扩展到其他地点和时间段。这种信风重建有可能极大地提高我们对信风变率及其对自然和人为强迫下全球气候变化影响的理解。

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.