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

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

• 批准号: 0327107
• 负责人: Ross Powell
• 金额: $ 10.67万
• 依托单位: Northern Illinois 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=0327107&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.

CowanOPP-0327106 Powell OPP-0327107 JaegerOPP-：0326926这是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)的首席研究人员共同提出的建议。北极科学的一个主要目标是量化近期气候变化对受到威胁的生态系统和土著文化的影响。在阿拉斯加，北太平洋(太平洋年代际涛动(PDO)、阿留申低压(Alpi)和北极涛动(AO)气候系统的这种气候强迫最强烈地表现为北极(60度-90度N)气温和降水的十年变化。这导致了区域海洋学的显著变化，特别是阿拉斯加冰川加速融化，这已被证明对海平面上升产生了全球影响，并可能对从阿拉斯加湾流入白令海的区域淡水输入产生影响。然而，冰川融化的时间和强迫无法确定，因为很少有直接从大型悬崖裂解冰川排放融水的年度记录，以测试冰川融化如何随着过去20年的高频气候变化而变化。智力上的优点：这项研究将在PDO和Alpi强迫最强的地区产生年度分辨率的气候记录，通过建立海洋植被厚度和当地气象强迫之间的关联，这种影响可能会影响到受到威胁的北极生态系统。对北美最大的潮水冰川哈伯德冰川的替代气候记录进行分析，将能够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。哈伯德冰川是进行实地研究的理想冰川，因为它相对稳定，位于气候敏感的地区，而且在亚肯色州的雅库塔特有很长(50多年)的当地气候学月度记录。一年一度的冰川形成于阿拉斯加湾沿岸与大型潮水冰川系统毗邻的前冰川盆地，由冬季冰山漂流产生的直径沉积后，夏季融水产生的层状泥浆沉积而成。需要检验的假设是，分层单元的厚度是哈伯德冰川夏季融水排放的替代。初步分析表明，PDO、Alpi与沉积速率之间存在一定的相关性，因此，负的(冷相)PDO指数与冬季较高的降雪量相关，从而导致夏季融化季节后期融水流量的增加。在1989年的气候变化之后，VARVE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，通过从醒幻湾采集了约30个活塞芯，产生了长达20年的假想VVE记录用于测试。沉积学和放射化学技术将建立不同的厚度和年代学。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，这将解决凹陷厚度如何随距离沉积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向阿拉斯加湾排放淡水方面的作用，这对阿拉斯加湾和白令海渔业的健康起着关键作用。这项建议还强调处于不同职业阶段的研究人员之间的合作，包括五名本科生，以及密歇根大学和北卡罗来纳大学的几名研究生，以培训学生学习地球科学。该项目还将通过与北卡罗来纳州西部的一个区域科学中心建立伙伴关系，制作一个摄影展示和一系列讲座，向成年观众介绍北极气候变化以及研究潮水冰川的方法，从而促进公民的外联活动。其中两位评审员不相信这个项目的结果会有大规模的意义。他们意识到，理解最近的融水排放记录作为特定环境变量的函数是重要的，例如，正如C-10页所述，但这似乎还不够重要。他们认为，更长期的观点应该是这项建议的一个更强大和更突出的因素--也许对短期记录的努力较小，对长期记录的努力更大。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，如果该项目只为一个实地赛季提供资金，则应考虑到这一点。也许这本应该写成一个为期三年的项目，有两个野外季节，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消退。