Fossil Coral Records of ENSO during the Last Glacial Period

末次冰期ENSO的珊瑚化石记录

基本信息

批准号：
1805874
负责人：
Judson Partin
金额：
$ 47.66万
依托单位：
University of Texas at Austin
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-09-01 至 2020-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1805874&HistoricalAwards=false
关键词：
Fossil Coral Records ENSO during

项目摘要

This project seeks to recover fossil corals from the island of Espiritu Santo, Vanuatu in the western tropical Pacific that will enable reconstruction of the El Nino/Southern Oscillation (ENSO) during the last glacial period using coral skeleton geochemistry. Few paleoclimate records exist that can resolve interannual changes during the Last Glacial Maximum (LGM), a time that can be used to help constrain the large uncertainty in ENSO's response to changes in global temperature. Corals provide one such record but fossil corals still in place from the LGM are normally found at water depths of 120-140 m below present sea level, and hence require expensive and logistically complex offshore approaches to obtain. In contrast, Vanuatu has experienced rapid rates of tectonic uplift which has raised the LGM paleo-shoreline to the point where glacial corals are expected to be near the surface and reachable by shallow drilling from onshore sites. The project thus offers a rare and important opportunity for the paleoceanographic community to acquire coral samples that can be used to develop high resolution time-series of ENSO and investigate western tropical Pacific variability during the LGM. The research team will modify an existing drill system to make it portable enough to hand-carry into hard to reach locations, and then conduct an extended field program to deploy and drill a series of onshore coral transects along the Vanuatu coast. U-Th dating will be used to confirm the ages of recovered corals and the samples obtained will be assessed for their suitability for later geochemical studies. The project will support an early career researcher as well as graduate and undergraduate students. Modern coral geochemical records from Vanuatu show a significant degree of skill in capturing the hydrological imprint of ENSO. Confidence in modern coral records suggest that fossil coral records can be used to estimate past changes in ENSO variability. On Vanuatu, tectonic uplift has raised the LGM paleo-shoreline to near present sea level, bringing old corals close to the surface as demonstrated by the research team's preliminary fieldwork. As part of this project, the team will build a new drill system that is portable, cost-efficient, and time-efficient for drilling shallow holes (5-25 m), a system that currently does not exist. The strategy will be to have a human-portable drill system that can be quickly moved to virtually any site to drill as many holes as possible, increasing the likelihood of recovering LGM coral material. The drilling operation will capitalize on an area where previous surveys have identified corals as old as 14.25 kyrs within a few meters of present sea level. A further advantage of applying this strategy to Vanuatu is that LGM corals are most likely still submerged in seawater rather than being uplifted completely onto dry land. This greatly reduces the chance for diagenetic alteration that all too often affects the geochemistry of older corals. The recovered coral samples will be dated using U-Th methods and screened for their geochemical integrity. The successful recovery of pristine glacial-age corals from Vanuatu will open the door for subsequent studies to determine how ENSO and tropical climate may have responded during the LGM, a time of greatly altered mean climate. An additional benefit for the larger community will be development and fabrication of the modified Winkie drill system. Such a portable system is expected to find considerable use by other researchers for land-based drilling operations in rough terrain.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.

该项目旨在从西部热带太平洋瓦努阿图的埃斯皮里图图岛恢复化石珊瑚，该岛将在最后一个冰川时期在最后一个冰川时期重建El Nino/Southern Oscillation（ENSO）。很少有古气候记录能够在最后一次冰川最大值（LGM）期间解决年际变化，这是可以用来帮助限制ENSO对全球温度变化的响应的巨大不确定性的时间。珊瑚提供了一个这样的记录，但通常在LGM中仍然存在的化石珊瑚，通常在当前海平面以下120-140 m的水深下发现，因此需要昂贵且具有逻辑上复杂的海上方法来获得。相比之下，瓦努阿图经历了构造隆起的迅速速率，这使LGM古平线提高到了冰川珊瑚的地面，并可以通过近海地点的浅钻孔到达地面并可以到达。因此，该项目为古文学界提供了一个罕见而重要的机会，以获取可用于开发ENSO高分辨率时间序列并研究LGM期间西部热带太平洋变异性的珊瑚样品。研究团队将修改现有的钻头系统，使其足够便携，以便将其交通困难以到达位置，然后进行扩展的现场计划，以部署和钻探一系列沿瓦努阿图海岸的陆上珊瑚样品。 U-th年代将用于确认回收的珊瑚的年龄，并将评估获得的样品，以适合其以后的地球化学研究。该项目将支持早期的职业研究员以及研究生和本科生。瓦努阿图的现代珊瑚地球化学记录显示了捕获ENSO水文烙印的重要技能。对现代珊瑚记录的信心表明，化石珊瑚记录可用于估计ENSO变异性的过去变化。在瓦努阿图（Vanuatu）上，构造隆起将LGM古平线提升到了近海平面，使旧珊瑚靠近地面，如研究小组的初步野外工作所证明的那样。作为该项目的一部分，该团队将建立一个新的钻探系统，该系统可用于钻孔（5-25 m）的便携式，具有成本效益且时间效率，该系统目前不存在。该策略将是拥有一个可快速移动到任何地点以尽可能多的孔的地点的人携带的钻系统，从而增加了恢复LGM珊瑚材料的可能性。钻井操作将利用以前调查确定珊瑚在当前海平面几米内的14.25公里的区域。将这种策略应用于瓦努阿图的另一个优点是，LGM珊瑚很可能仍被淹没在海水中，而不是完全升高到干燥的土地上。这大大减少了成岩成分改变的机会，这常常会影响老年珊瑚的地球化学。回收的珊瑚样品将使用U-Th方法进行日期，并筛选其地球化学完整性。从瓦努阿图（Vanuatu）成功恢复原始冰川时代的珊瑚将为随后的研究打开大门，以确定在LGM期间ENSO和热带气候如何反应，这是平均气候大大改变的时期。更大的社区的另一个好处将是修改后的Winkie演习系统的开发和制造。预计这种便携式系统将在粗糙地形中发现其他研究人员对陆基钻井作业的大量用途。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的评估标准通过评估来支持的。