Meltwater Discharge in the Arctic During the Deglacial Period

本文的主要研究者将通过建立一个AMS测年的N.通过d18 O和沉积物岩性，以及过去15，000年的地球化学，将记录来自北方劳伦泰德冰盖的低d18 O水融化的入侵。以前的稳定同位素重建表明，在北极盆地中部的融水排放的影响是大的，沉积学研究跟踪两个冰筏碎片事件从北方加拿大的弗拉姆海峡在冰消期。这些结果意味着，北极盐度的变化可能发挥了重要作用，在北大西洋翻转环流的变化。这些融水事件应该在N. pachyderma d18 O和异常的大小应成比例的融水事件的大小。这些岩心于1989年收集，并存档在伍兹霍尔海洋研究所岩心储存库。它们的状况很好，没有取样。根据颜色的变化，核心沉积速率（~1至3厘米kyr-1）允许开发一个相对高分辨率的记录冰消期融水排放。智力优势。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的敏感性如何？对未来气候的准确预测需要这些知识，但过去大西洋翻转变化的最好例子是地质记录。大西洋盐度的变化可能会影响到北大西洋的环流和热量输送：在过去的40年里，高纬度地区一直在以前所未有的方式清新，格陵兰海对流可能已经开始减少。然而，很难知道需要多大的盐度变化才能显著改变环流。物理海洋学家不确定，对未来温室气候的大量数值模拟预测了一系列结果，从没有改变到大西洋的15 Sv减少。为了充分了解环流对盐度变化的敏感程度，需要研究地质记录和北冰洋在这些变化中的作用的具体知识。 更广泛的影响。研究生培训是该项目的重要组成部分。Sharon霍夫曼（二年级研究生）将为堆芯提供钍数据。 额外的培训将包括高中参与者获得的研究经验，他们将参与本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，本科生课程以及海洋科学新闻研究员的年度WHOI媒体聚会。 最近对杂志（《发现》、《新闻周刊》）、报纸（《波士顿地球仪》、《华尔街日报》）和广播电台（当地NPR电台）的采访证明了这项研究结果可能会被讨论的地方。首席研究员在华盛顿和伍兹霍尔向众议院、参议院及其工作人员介绍了气候简报和正式证词。

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.