P2C2: Rapid Climate Variations--A Speleothem-based High-resolution Record of Rainfall in the Equatorial South Pacific over the Last 83,000 Years

该项目旨在利用纽埃岛和汤加的石笋，以亚世纪（~50年/样本）分辨率生成热带太平洋南部大部分冰川期和全新世时期的铀/钍（U/Th）年代记录。纽埃的洞穴可以追溯到距今83000年前。具体来说，研究人员将：1)分析纽埃标本，以及来自汤加的全新世石笋，测定氧-18、碳-13、镁/钙比率、锶/钙比率和钡/钙比率；2)建立了精确的U/Th绝对年代模型；3)进行滴水取样以验证古气候解释。该项目的目标是检验以下假设：a)在温盐环流（THC）增加的时候，太平洋热带辐合带（ITCZ）向北移动主导了沃克小圈向西移动，导致纽埃的降雨量减少；b)纽埃的降雨记录将显示与格陵兰冰芯记录相一致的快速变化，但也将显示南极温度记录的额外变化特征。更广泛的影响包括从一个重要且研究不足的地区获得高质量古气候记录的潜力。除了科学重要性和研究生的支持外，研究人员还将通过nsf赞助的项目进行推广，该项目由新泽西州的高中生和教师参加海洋和气候科学研讨会。

This project seeks to generate a Uranium/Thorium (U/Th) dated record of rainfall in the southern tropical Pacific at sub-century (~50 year/sample) resolution for most of the glacial and Holocene periods using stalagmites from the island of Niue and from Tonga. The speleothem from Niue dates to 83,000 years before the present. Specifically, the researchers will: 1) analyze the Niue specimen, as well as a Holocene-age stalagmite from Tonga, for Oxygen-18, Carbon-13, Magnesium/Calcium ratios, Strontium/Calcium ratios, and Barium/Calcium ratios; 2) generate a precise absolute-dated U/Th age model for the specimens; and 3) undertake drip-water sampling to validate paleoclimate interpretations. The goal of the project is to examine the following hypotheses: a) at times of increased Thermohaline Circulation (THC), a northward shift of the Pacific Inter-tropical Convergence Zone (ITCZ) dominated over a westward shift in the Walker Cell resulting in decreased rainfall at Niue; and b) rainfall records at Niue will show rapid shifts in phase with Greenland ice-core records, but will also show additional changes characteristic of Antarctic temperature records.The broader impacts include the potential for a high-quality paleoclimate record from an important and under-studied region. In addition to the scientific importance and support of a graduate student, the researcher will conduct outreach through a NSF-sponsored program through which high-school students and teachers from New Jersey participate in workshops on marine and climate science.