Meltwater Discharge in the Arctic During the Deglacial Period

冰消期北极融水排放

• 批准号: 0520073
• 负责人: William Curry
• 金额: $ 31.92万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-15 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0520073&HistoricalAwards=false
• 关键词: Meltwater; Discharge; Arctic; During; Deglacial

ABSTRACTCurryOPP-0520073The Principal Investigator will construct a history of meltwater discharge into the Arctic Ocean through the Mackenzie River system during the most recent deglaciation by developing an AMS-dated chronology of N. pachyderma by d18 O and sediment lithology, and geochemistry for the last 15,000 years which will record the incursion of low- d18 O water melting from the northern Laurentide Ice Sheet. Previous stable isotopic reconstructions show that the effects of meltwater discharge in the central Arctic basin were large and sedimentological studies trace two ice rafted debris events from northern Canada to the Fram Strait during the deglacial period. These results imply that changes in Arctic salinity likely played a major role in the variability of North Atlantic overturning circulation. These meltwater events should show up as minima in N. pachyderma d18 O and the magnitude of the anomalies should be proportional to the size of the meltwater event. The cores were collected in 1989 and archived in the Woods Hole Oceanographic Institution core repository. They are in excellent condition and remain unsampled. Based on color changes, core sedimentation rates (~1 to 3 cm kyr-1) permit the development of a relatively high-resolution record of deglacial meltwater discharge. Intellectual Merit. This research will provide insight into a very important climate question: how sensitive is the Atlantic overturning circulation to reduced salinity in the Arctic Ocean and subpolar North Atlantic? Accurate future projections of climate require this knowledge, yet the best examples of past changes in Atlantic overturning are in the geological record. Atlantic salinity is changing in ways that may affect circulation and heat transport to the North Atlantic: high latitude locations have been freshening for the last forty years in ways never before documented and reduced Greenland Sea convection may already be underway. However, it is difficult to know how much of a salinity change is needed to alter the circulation significantly. Physical oceanographers are unsure and the numerous numerical simulations of future greenhouse climate predict a full range of outcomes from no change in the overturning to a 15 Sv reduction in the Atlantic. To fully understand how sensitive the circulation is to changing salinity requires study of the geological record and specific knowledge of the Arctic Ocean's role in these changes. Broader Impacts. Graduate student training is a significant part of this project. Sharon Hoffman, (a second year graduate student) will produce the thorium data for the cores. Additional training will include the research experiences gained by the high school participants who will be involved with sample preparation and analytical procedures for this project. The Principal Investigator regularly speaks before the public in a variety of venues, including public libraries, undergraduate classes, and at annual WHOI gathering of media for Ocean Science Journalism Fellows. Recent interviews with magazines (Discover, Newsweek), newspapers (Boston Globe, Wall Street Journal) and radio (local NPR station) attest to the places where the results of this research are likely to be discussed. The Principal Investigator has presented climate briefings and formal testimony to members of the House of Representatives, the Senate, and their staffs in Washington, DC and at Woods Hole.

摘要CurryOPP-0520073首席研究员将通过 d18 O 和沉积物岩性以及过去 15,000 年的地球化学来开发 AMS 测年的厚皮猪笼草年表，从而记录来自北部的低 d18 O 水融化的入侵，从而构建最近一次冰消期期间融水通过麦肯齐河系统排入北冰洋的历史。劳伦泰冰 床单。先前的稳定同位素重建表明，北极中部盆地融水排放的影响很大，沉积学研究追踪了冰消期期间从加拿大北部到弗拉姆海峡的两次冰筏碎片事件。这些结果意味着北极盐度的变化可能在北大西洋翻转环流的变化中发挥了重要作用。这些融水事件在厚皮猪笼草 d18 O 中应显示为最小值，并且异常的幅度应与融水事件的大小成正比。这些岩心于 1989 年收集并存档于伍兹霍尔海洋研究所核心存储库中。它们状况良好且未经过取样。根据颜色变化，岩心沉积速率（~1 至 3 cm kyr-1）允许开发相对高分辨率的冰消融水排放记录。智力优点。这项研究将深入了解一个非常重要的气候问题：大西洋翻转环流对北冰洋和副极地北大西洋盐度降低有多敏感？对未来气候的准确预测需要这些知识，而过去大西洋翻转变化的最佳例子是在地质记录中。大西洋盐度正在发生变化，可能会影响北大西洋的循环和热量传输：过去四十年来，高纬度地区一直在以前所未有的方式变得清新，格陵兰海对流可能已经开始减少。然而，很难知道需要改变多少盐度才能显着改变循环。物理海洋学家并不确定，对未来温室气候的大量数值模拟预测了一系列结果，从翻转没有变化到大西洋减少 15 西弗。要充分了解环流对盐度变化的敏感程度，需要研究地质记录并了解北冰洋在这些变化中的作用。 更广泛的影响。研究生培养是该项目的重要组成部分。 Sharon Hoffman（二年级研究生）将生成堆芯的钍数据。 额外的培训将包括高中参与者获得的研究经验，他们将参与该项目的样品制备和分析程序。首席研究员定期在各种场所向公众发表演讲，包括公共图书馆、本科生课程以及年度 WHOI 海洋科学新闻研究员媒体聚会。 最近对杂志（《Discover》、《新闻周刊》）、报纸（《波士顿环球报》、《华尔街日报》）和广播电台（当地 NPR 电台）的采访证明了可能会讨论这项研究结果的地方。首席研究员已向华盛顿特区和伍兹霍尔的众议院、参议院成员及其工作人员提供了气候简报和正式证词。