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

合作研究：建立海洋藻类厚度作为年度气候变化和 PDO 振荡的代理，哈伯德冰川实地研究

• 批准号: 0327106
• 负责人: Ellen Cowan
• 金额: $ 4.39万
• 依托单位: Appalachian State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-01 至 2006-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0327106&HistoricalAwards=false
• 关键词: Collaborative; Research; Establishing; Marine; Varve

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.

这是由阿巴拉契亚州立大学、北方伊利诺斯大学（NIU）和佛罗里达大学（UF）的主要研究者共同提出的一项合作建议。 北极科学的一个主要目标是量化近期气候变化对受威胁的生态系统和土著文化的影响。在阿拉斯加，北太平洋（太平洋十年涛动（PDO））、阿留申低气压（ALPI）和北极涛动（AO）气候系统的这种气候强迫最强烈地表现在北极（北纬60度-90度）气温和降水的十年变化上。这导致了区域海洋学的显著变化，阿拉斯加冰川明显加速融化，这已被证明对海平面上升以及可能对从阿拉斯加湾流入白令海的区域淡水产生了全球性影响。然而，冰川融化的时间和动力尚无法确定，因为几乎没有直接从大型悬崖崩解冰川中排出的融水的年度记录，以测试冰川融化如何响应过去二十年的高频率气候变化。这项研究将每年产生-在PDO和ALPI强迫最强的地区，通过建立海洋纹层厚度和当地气象之间的相关性，解决了气候记录，其影响可能会影响受威胁的北极生态系统强迫。对北美最大的冰川哈伯德冰川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度释放最密切相关。哈伯德冰川是进行实地研究的理想冰川，因为它相对稳定，位于气候敏感地区，并且在AK的Yakutat有长期（50年以上）的当地气候记录。年度纹层形成于与阿拉斯加湾沿岸沿着大型潮水冰川系统相邻的冰前盆地中，由夏季沉积的融水产生的层压泥和冬季沉积的冰山漂流产生的二米克斯组成。要测试的假设是，层压单位的厚度是夏季从哈伯德冰川融水排放代理。纹层厚度的初步分析表明PDO，ALPI，和沉积速率之间的相关性，负（冷相）PDO指数与较高的冬季降雪量，导致增加融水排放后，在夏季融化季节。在1989年政权转移后，纹状记录也与较高的夏季降水量相关，这是1989年后ALP指数的一个特征。利用这些关系，一个长达20年的假设纹记录已被收集的30活塞岩心从祛魅湾测试。沉积学和放射化学技术将确定纹层厚度和年代。将收集高分辨率地震反射剖面图，以增加空间覆盖面和相关性，这将解决纹层厚度如何随着与沉积物来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关键作用。该提案还强调了研究人员在其职业生涯的各个阶段，包括五名本科生之间的合作，以及在UF和NIU的几名研究生，培养学生在地球科学。该项目还将与北卡罗来纳州西部的一个区域科学中心建立伙伴关系，制作图片展览和系列讲座，向成年观众宣传北极气候变化以及研究冰川的方法，从而促进公民外联。两名评审员不相信该项目的结果将具有大规模的意义。他们意识到，了解最近记录的融水排放作为一个特定的环境变量的函数是重要的，如第C-10页所描述的，但这似乎还不够重要。 他们认为，从长远角度看问题，本应是这一提案中更有力、更突出的要素-也许在短期记录方面应少做一些努力，在长期记录方面应多做一些努力。 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，如果该项目仅为一个实地季节提供资金，则应考虑到这一点。也许这应该被写成一个为期三年的项目，有两个实地季节，更多的讨论为什么以及如何长期的数据集将帮助我们把现代冰川退缩的角度。