Establishing extraterrestrial 3He as a Plio-Pleistocene constant flux proxy

保存在海底沉积物中的风尘、生物物质和热液矿物的沉积通量记录为研究大气、海洋、生物地球化学和固体地球对过去气候条件的响应提供了宝贵的约束条件。然而，由于海底沉积物的重新分布，这样的记录可能会很复杂。为了可靠地构建和解释过去气候变化的这种沉积记录，需要恒定通量指标(CFP)。然而，到目前为止，还没有为研究50万年前的气候系统而校准的CFP。在这个项目中，研究人员将评估和校准外星氦-3(3Heet)，以用作过去500万年地球历史上的CFP，即上更新世。上更新世包括全球气候系统的许多重大转变，以及比现代气候条件更温暖的多个时期。这项研究将开发一种新的方法，在帮助理解过去的气候变化和预测未来气候系统对全球变暖的反应方面可能有广泛的应用。Funding支持没有NSF支持的早期职业研究人员，并将通过Lamont-Doherty中学野外研究计划吸引来自代表性不足群体的学生。恒通量指标是古海洋学不可分割的一部分，因为CFP得出的质量积累速率与横向沉积物传输偏差无关，后者可能会混淆传统的年龄模型得出的质量积累速率记录。3HeET具有作为上更新世CFP的潜力，但由于缺乏对这段时间内全球3HeET流入的限制，该方法的当前应用受到限制。该项目将通过使用沉积铍-10(10Be)校准过去5百万年的全球3HeET流入，开发第一个用于上更新世海洋学的恒定通量替代物。研究人员将通过在来自低颗粒通量海洋区域的现有沉积物岩心中产生三个跨度为0.5至5 Ma的基于10Be的3HeET流入记录来限制全球3HeET的流入，这些区域的上更新世10Be沉积速率的变化预计最小。预期结果将使社区能够在广泛的动态沉积环境中应用3HeET，从而在海洋地质学和地球物理学的各种主题中开辟新的前沿，包括：古海洋学、古气候、海洋沉积学和沉积物运输，以及海底火山学和气候之间的长期相互作用。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Deposition flux records of windblown dust, biologic material, and hydrothermal minerals preserved in seafloor sediments yield valuable constraints with which to investigate atmospheric, oceanographic, biogeochemical, and solid Earth responses to past climate conditions. However, such records can be complicated because of the redistribution of sediments on the seafloor. Constant flux proxies (CFPs) are required for the reliable construction and interpretation of such sedimentary records of past climate variability. To date, however, there are no CFPs calibrated for the examination of the climate system prior to 500,000 years ago. In this project, investigators will evaluate and calibrate extraterrestrial helium-3 (3HeET) for use as a CFP over the past 5 million years of Earth history, known as the Plio-Pleistocene. The Plio-Pleistocene includes many major transitions in the global climate system as well as multiple episodes of warmer than modern climate conditions. This research will develop a new method that could have broad applications in helping to understand past climate change and predicting future climate system responses to a warming world. Funding supports an early career researcher with no prior NSF support, and will engage students from underrepresented groups through the Lamont-Doherty Secondary School Field Research Program.Constant flux proxies are an integral part of paleoceanography because CFP-derived mass accumulation rates are independent of the lateral sediment transport biases that can confound traditional age model-derived mass accumulation rate records. 3HeET has the potential to serve as a Plio-Pleistocene CFP, but current applications of this method are limited by the lack of constraints on the global 3HeET influx over this time period. This project will develop the first constant flux proxy for Plio-Pleistocene oceanography by calibrating the global 3HeET influx over the past 5 Myr using sedimentary beryllium-10 (10Be). Investigators will constrain the global 3HeET influx by generating three 10Be-based 3HeET influx records spanning 0.5 to 5 Ma in existing sediment cores from low particle flux ocean regions, where Plio-Pleistocene variations in 10Be deposition rates are expected to be minimal. Anticipated results will enable the community to employ 3HeET in Plio-Pleistocene applications spanning a wide range of dynamic depositional environments and thus enable new frontiers in a variety of topics in marine geology and geophysics, including: paleoceanography, paleoclimate, marine sedimentology and sediment transport, as well long-term interactions between submarine volcanology and climate.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.