Collaborative Research: Establishing Marine Varve Thickness as a Proxy for Annual Alaska Climate Variability and PDO Oscillations, Hubbard Glacier Field Study

这是由阿巴拉契亚州立大学、北伊利诺伊大学（NIU）和佛罗里达大学（UF）的主要研究人员共同提出的一项合作提案。北极科学的一个主要目标是量化最近气候变化对受威胁的生态系统和当地文化的影响。在阿拉斯加，这种气候强迫由北太平洋（太平洋年代际振荡（PDO））；阿留申低压（ALPI）和北极涛动（AO）气候系统在北极气温和降水（60 -90度）的年代际变化中表现得最为强烈。这导致了区域海洋学的显著变化，特别是阿拉斯加冰川的加速融化，这已被证明对海平面上升产生了全球性影响，也许还对从阿拉斯加湾流入白令海的区域淡水产生了影响。然而，冰川融化的时间和强迫无法确定，因为很少有大型悬崖崩解冰川直接释放融水的年度记录，以测试冰川融化如何响应过去20年的高频气候变化。知识价值：这项研究将通过建立海洋厚度与当地气象强迫之间的相关性，在PDO和ALPI强迫最强的地区产生年度解决的气候记录，并可能影响受威胁的北极生态系统。对北美最大的潮汐冰川哈伯德冰川（Hubbard Glacier）的代用气候记录进行分析，将有助于评估哪些气候变量或指数与沉积物和融水的年释放最密切相关。哈伯德冰川是一个理想的实地研究冰川，因为它相对稳定，位于气候敏感地区，并且在雅库塔有很长的（50多年）当地气候的月度记录。在靠近阿拉斯加湾沿岸的大型潮汐冰川系统的前冰川盆地中形成了年轮，夏季由融水产生的层状泥沉积，冬季由冰山漂流产生的碎屑沉积。要验证的假设是，叠层单元的厚度是哈伯德冰川夏季融水流量的代表。阀厚的初步分析显示PDO、ALPI和沉降速率之间存在相关性，因此负（冷相）PDO指数与冬季降雪量增加相关，导致夏季融化期后期融水流量增加。经过1989年的变化后，阀记录也与较高的夏季降水相关，这是1989年后ALP指数的一个特征。利用这些关系，通过收集来自Disenchantment Bay的约30个活塞岩心，产生了一个长达20年的假设阀门记录进行测试。沉积学和放射化学技术将确定地层厚度和年代学。将收集高分辨率地震反射剖面，以增加空间覆盖率和相关性，这将解决阀厚度随距离沉积物源的距离而变化的问题。更广泛的影响将包括更好地了解冰川融化在影响阿拉斯加湾淡水排放方面的作用，这对阿拉斯加湾和白令海的渔业健康起着至关重要的作用。该提案还强调了在不同职业阶段的研究人员之间的合作，包括佛罗里达大学和NIU的五名本科生和几名研究生，以培养地球科学方面的学生。该项目还将通过与北卡罗莱纳西部的一个区域科学中心建立伙伴关系，制作一个摄影展览和一系列讲座，向成年观众宣传北极气候变化以及研究潮汐冰川的方法，从而促进公民外展。其中两名审稿人不相信该项目的结果将具有大规模意义。他们意识到，理解融水排放的最近记录作为特定环境变量的函数是很重要的，如C-10页所述，但这似乎还不够重要。他们认为，更长远的观点应该是这个提案中更强有力和更突出的因素，也许应该在短期记录上少做些努力，而在长期记录上多做些努力。虽然短记录对于开发解释旧记录的工具至关重要，但他们建议，如果该项目仅为单个油田季节提供资金，则应考虑到这一点。也许这应该写成一个为期三年的项目，有两个实地季节，并更多地讨论为什么以及如何更长期的数据集将帮助我们正确看待现代冰川退缩。

ABSTRACTCowanOPP-0327106Powell OPP-0327107 JaegerOPP-: 0326926 This is a collaborative proposal by Principal Investigators at the Appalachian State University, Northern Illinois University (NIU), and the University of Florida (UF). A major goal of Arctic science is to quantify the impact of recent climate change on threatened ecosystems and native cultures. In Alaska, this climate forcing by North Pacific (Pacific Decadal Oscillation (PDO); Aleutian Low Pressure (ALPI), and Arctic Oscillation (AO) climate systems is most strongly manifested in decadal-long shifts in Arctic (60degrees-90degreesN) air temperature and precipitation. This has led to pronounced changes in regional oceanography and noticeably in the accelerated melting of Alaskan glaciers, which has been shown to have a global impact on sea-level rise and perhaps on regional freshwater input to the Bering Sea from the Gulf of Alaska. However, the timing and forcing of glacial melting cannot be established, because there are few annual records of meltwater discharge directly from large cliff-calving glaciers to test how glacier melt varies in response to high-frequency climate change over the last two decades.Intellectual Merit: This research will generate annually-resolved climate records in an area where forcing by the PDO and ALPI is strongest and the impact is likely to affect threatened Arctic ecosystems by establishing a correlation between marine varve thickness and local meteorological forcing. Analysis of the proxy climate record at Hubbard Glacier, the largest tidewater glacier in North America, will allow evaluation of what climate variables or indices most closely correlate with annual release of sediment and meltwater. The Hubbard is an ideal glacier for a field study because it is relatively stable, is located in a climatically sensitive region, and there is a long (50+ year) monthly record of local climatology in Yakutat, AK. Annual varves form in proglacial basins adjacent to large tidewater glacier systems along the Gulf of Alaska coast and consist of summer deposition of meltwater-produced laminated mud following winter deposition of a diamicton produced by iceberg rafting. The hypothesis to be tested is that the thickness of the laminated unit is a proxy for summer meltwater discharge from Hubbard Glacier. Preliminary analysis of varve thickness shows a correlation between PDO, ALPI, and sedimentation rate, such that the negative (cold-phase) PDO index correlates with higher winter snowfall leading to increased meltwater discharge later in the summer melt season. After a 1989 regime shift, the varve record also correlates with higher summer precipitation, a characteristic of the post-1989 ALP index. By using these relationships, a 20-year long hypothetical varve record has been produced for testing by collecting ~30 piston cores from Disenchantment Bay. Sedimentological and radiochemical techniques will establish varve thickness and chronology. High resolution seismic reflection profiles will be collected to increase spatial coverage and correlation, which will address how varve thickness varies as a function of distance from the sediment source. The Broader Impacts will include improved understanding of the role of glacial melting in influencing the freshwater discharge to the Gulf of Alaska, which plays a critical role in the health of fisheries within the Gulf of Alaska and Bering Sea. This proposal also emphasizes collaboration among researchers at various stages of their careers, including five undergraduate students, and several graduate students at UF and NIU, to train students in the earth sciences. This project will also contribute to citizen outreach by establishing a partnership with a regional science center in Western North Carolina to produce a photographic display and a lecture series to communicate Arctic climate change as well as methods used to study tidewater glaciers to an adult audience. Two of the reviewers are not convinced that the results of this project will be of large scale significance. They realize that understanding the recent record of meltwater discharge as a function of specific environmental variables is important, as described on page C-10 for example, but this just does not seem important enough. They think that a longer term perspective should have been a stronger and more prominent element of this proposal - with perhaps a smaller effort on the short record and a greater effort on longer records. While the short record is critical for developing the tools to interpret older records, they recommend that this be taken into consideration should this project be funded for only a single field season. Perhaps this should have been written as a three year project, with two field seasons, and more discussion of why and how a longer term data set would help us put modern day glacial retreat into perspective.