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

作为一项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。这些数据将用于解释岩心中保存下来的沉积特征，这些岩心的记录一直延续到上个世纪，在这一时期，存在着相对可靠的流量、气候和海洋条件的仪器记录。最终，人们希望这项研究的结果能够对过去几千年的气候驱动因素进行高分辨率的表征。这些知识将进一步了解该系统在过去是如何响应的，并可能提供有关未来气候变化的关键预测信息。此外，本研究的一个关键外展组成部分是开发一套教学课程，供阿拉斯加农村地区缺乏服务的人口使用，这些人口获得科学教育或当前研究的机会有限。该项目旨在让学生进一步了解科学家如何利用沉积物岩心来确定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。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，对生态和经济产生了深远的影响。本研究旨在利用PWS沉积物中包含的高分辨率环境记录的潜力，这可能使我们了解整个全新世不断变化的河流沉积物扩散和/或气候驱动的海洋学模式。先前的x射线荧光（XRF）分析表明，PWS沉积物岩心包含地球化学和沉积学特征，可以潜在地解决不同的源输入。元素比值（如Sr/Mn、Zn/S、K/Ca）可作为区分Chugach/northern PWS沉积物负荷与上游铜河沉积物负荷的依据。然而，主要流域内的成分变化信息缺乏，了解铜河流量受变化的物源/淡水来源（如雪融水、冰川融水和降雨，Chugach与Wrangell ranges）影响的季节变化对环境代理记录的发展至关重要。一旦受到限制，这些代用物就有可能在次年到十年的时间尺度上解决气候振荡。因此，本项目的重点是收集PWS和铜河流域沉积物的代表性样品的高分辨率时间序列，目的是自信地约束沉积物岩心XRF记录中观察到的元素变化。悬浮物浓度的元素组成将使用电感耦合等离子体质谱（ICPMS）测定。还将对样品进行宇宙成因分析，以验证这样一种假设，即在春季排放/冰川融化期间，普遍用于近期河流沉积的示踪剂可能在高纬度地区存在问题。

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.