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

该项目旨在利用来自纽埃岛和汤加的石笋，以亚世纪（~50年/样本）分辨率生成南太平洋热带地区大部分冰期和全新世时期降雨的铀/钍（U/Th）定年记录。 纽埃的洞穴化石可以追溯到距今83,000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，氧-18，碳-13，镁/钙比率，锶/钙比率和钡/钙比率; 2）为标本生成精确的绝对年代U/Th年龄模型;和3）进行滴水采样以验证古气候解释。该项目的目标是检验以下假设：a）在温盐环流增加时，太平洋热带辐合带的北移超过步行者环流圈的向西移，导致纽埃降雨量减少;和B）纽埃的降雨记录将显示与格陵兰冰芯记录的相位迅速变化，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的和未得到充分研究的地区获得高质量古气候记录的潜力。除了研究生的科学重要性和支持外，研究人员还将通过NSF赞助的项目进行推广，通过该项目，来自新泽西的高中学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.