Geochemical Characterization of Prince William Sound and Copper River Sediments: A Proxy Development to Assess Climate-Driven Variations in a High-Resolution Sedimentary Record

作为为期两年的博士后研究奖学金的一部分，该项目侧重于通过分析不同环境条件下的时间序列来确定威廉王子湾(PWS)和铜河沉积物的元素组成。这些数据将被用来解释岩芯中保存下来的沉积特征，其记录可以追溯到上个世纪，而上个世纪是存在相对可靠的流量、气候和海洋条件仪器记录的时期。最终，人们希望这项研究的结果能够高分辨率地描述过去几千年的气候驱动因素。这一知识将进一步了解该系统在过去是如何响应的，并可能提供关于未来气候变化的关键预测信息。此外，这项研究的一个关键外展部分是开发一个教学课程，供阿拉斯加农村地区服务不足的人口使用，这些人获得科学教育或目前的研究机会有限。该项目旨在加深学生对科学家如何使用沉积物岩芯来确定PWS和北太平洋的气候趋势，以及随后对渔业分布、生存和商业收获的影响的理解。该项目将在弗吉尼亚海洋科学研究所的Steven A.Kuehl博士的指导下进行。PWS是一个敏感的亚北极地区，快速变化的气候模式强烈地改变了水文和海洋条件，具有深刻的生态和经济影响。这项研究试图挖掘PWS沉积物中包含的高分辨率环境记录的潜力，这可能使我们能够了解整个全新世河流沉积物扩散和/或气候驱动的海洋学模式的变化。以前的X射线荧光(XRF)分析表明，PWS沉积物岩心含有地球化学和沉积学特征，有可能解决不同来源的输入问题。元素比值(如：锶/锰、锌/S、钾/钙)可作为区分楚加赫/北普里斯河泥沙与铜河上游泥沙负荷的依据。然而，关于主要流域内成分变化的信息很少，了解铜河流量中不同来源/淡水来源(例如，积雪融化、冰川融化和降雨量、丘加赫山脉与朗格尔山脉)影响的季节变化对于开发环境替代记录至关重要。一旦受到限制，这些指标就有可能解决亚年度到十年时间尺度上的气候振荡。因此，本项目的重点是收集具有代表性的PWS和铜河流域沉积物样品的高分辨率时间序列，目的是确信地约束在沉积物岩心XRF记录中观察到的元素变化。悬浮泥沙浓度的元素组成将使用电感耦合等离子体质谱(ICPMS)进行测定。还将对样品进行宇宙成因7Be的分析，以检验这样一种假设，即在春季排放/冰川融化期间，普遍使用的近期河流沉积示踪剂在高纬度环境下可能存在问题。

As part of a two-year postdoctoral research fellowship, this project focuses on determining the elemental composition of Prince William Sound (PWS) and Copper River sediments by analyzing a time-series throughout varying environmental conditions. These data will be used to interpret preserved sedimentary signatures contained within cores whose record extends into the last century, the period for which relatively robust instrumental records of discharge, climate, and oceanographic conditions exist. Ultimately, it is hoped the results of this research will allow high-resolution characterization of climatic drivers over the last several millennia. This knowledge will further understanding of how this system has responded in the past, and may provide crucial predictive information concerning future climate variations. Additionally, a key outreach component for this study is the development of a teaching curriculum to be used by underserved populations within rural Alaska who have limited access to science education or current research. The program will aim to further student understanding of how scientists use sediment cores to identify climate trends in PWS and the northern Pacific Ocean, and the subsequent impact on fisheries distribution, subsistence, and commercial harvests. This project will be conducted under the mentorship of Dr. Steven A. Kuehl at the Virginia Institute of Marine Science.The PWS is a sensitive sub-arctic region where rapidly changing climate patterns strongly alter hydrological and oceanographic conditions in ways that have profound ecological and economical implications. This research seeks to exploit the potential for a high-resolution environmental record contained within PWS sediment, which may allow us to understand changing river sediment dispersal and/or climate-driven oceanographic patterns throughout the Holocene. Previous X-ray Fluorescence (XRF) analyses reveal that PWS sediment cores contain geochemical and sedimentological signatures that can potentially resolve varying source input. Elemental ratios (e.g. Sr/Mn, Zn/S, K/Ca) may provide a basis for differentiating Chugach/northern PWS derived sediment loads from those of the upper Copper River. However, there is a paucity of information on compositional variations within the major drainage basins, and understanding seasonal variability influenced by changing provenance/ freshwater sources (e.g., snow melt, glacial melt, and rainfall, Chugach vs. Wrangell Range) in Copper River discharge is critical for the development of environmental proxy records. Once constrained, these proxies have the potential to resolve climatic oscillations on sub-annual to decadal timescales. Therefore, this project focuses on collecting a high-resolution time-series of representative samples of PWS and Copper River basin sediments with the aim to confidently constrain elemental variations observed in sediment core XRF records. Elemental composition of suspended sediment concentrations will be determined using Inductively Coupled Plasma Mass Spectrometry (ICPMS). Samples will also be analyzed for cosmogenic 7Be to test the hypothesis that the ubiquitously used tracer for recent fluvial sedimentation may be problematic in high latitude settings during spring discharge/ glacial melt.