Water Masses, Circulation Patterns, and Variability in the Central Arctic Ocean: Tracer Studeis (Tritium/3He, Oxygen Isotopes, and 14C) During the 2005 Arctic Section

这项工作将支持在瑞典破冰船ODEN计划的2005年跨北极巡航期间对示踪剂（氚/3He，氧同位素和14C）的收集，测量和分析，可能是与美国破冰船Healy一起进行的两船行动。这条航线将穿越整个北极中部，从阿拉斯加大陆架开始，穿过加拿大盆地中部，到达极地，从那里穿过欧亚盆地，到达巴伦支海以北的大陆架。该部分首次提供了在加拿大盆地中部获得高质量、高分辨率、全深度多示踪剂数据集的机会。在ODEN计划进行的水文/示踪计划的背景下，pi将收集和测量900个氚和氦同位素，720个氧同位素和120个放射性碳（14C）样本。这些样品的数量被调整到与单个示踪剂测量处理的科学目标。瑞典同事慷慨地在奥登为收集示踪剂样品的人员提供住宿。拟议的工作将通过提供来自采样不足的加拿大盆地的第一个高质量示踪剂数据集，大大加强北冰洋示踪剂研究。它们还可以让我们看到欧亚盆地的年代际变化。最后，这些数据将提供全球CLIVAR/碳重复水文计划在北纬高纬度地区的扩展，并将代表一个坚实的基线，未来的剖面可以与之比较，研究北极可能的人为驱动的变化。示踪剂数据将用于解决下列科学问题：(a)确定北冰洋主要盆地和淡水来源（大气水（河流径流和降水）、海冰融水和白令海峡流入）的淡水分布和库存。(b)探讨南森和阿蒙森流域淡水储量与1991年和1996年所占河段淡水储量的变化（年代际变化）。(c)确定上层水域（表层、盐跃层和源自大西洋的水域）的环流型态。(d)检查北冰洋中部的中深度环流型态。(e)确定加拿大盆地深水的平均停留时间和年龄梯度。示踪数据的收集和解释将与ODEN上的其他海洋学项目密切合作。该方案解决了ARCSS、SEARCH和ASOF以及高纬度CLIVAR的目标。更广泛的影响：该计划将有助于确定最近在北极记录的广泛变化在多大程度上是自然变率或人类活动引起的变化的一部分。这个问题具有重要的社会意义，因为北极系统的新状态的变化将对气候和经济产生全球影响。许多指标暗示了后一种情况，但我们仍然缺乏人为驱动北极系统变化的科学确定性。其他更广泛的影响包括来自北极的高质量数据集的可用性，这些数据集将用于汇集气候和碳研究的全球数据集（示踪剂测量是估计海洋中人为碳量的重要因素）。在教育方面，这些数据将提供给研究高纬度问题的学生，结果将公布在一个网站上。这些材料也经常用于哥伦比亚大学的高级课程。该材料通常用于示踪海洋学或环境示踪技术课程的案例研究。这些数据也被学生用于学期论文或习题集。最后，pi正在与高中建立一个项目，通过让学生参与拟议工作的每个部分，让他们密切关注科学知识的发展。

This work will support the collection, measurement and analysis of tracers (tritium/3He, oxygen isotopes, and 14C) during the planned 2005 trans-Arctic cruise of the Swedish icebreaker ODEN, likely as a two-ship operation with the US Icebreaker Healy. The cruise track will cross the entire central Arctic, starting from the Alaskan Shelf crossing the central Canadian Basin to the Pole, from where it leads across the Eurasian Basin to the continental shelf north of the Barents Sea. This section offers the first opportunity to obtain a high-quality, high-resolution, full-depth multi-tracer data set in the central Canada Basin. In the context of the hydrography/tracer program scheduled to be carried out from the ODEN the PIs will collect and measure 900 tritium and helium isotope, 720 oxygen isotope, and 120 radiocarbon (14C) samples. These numbers of samples are adjusted to the scientific goals addressed with the individual tracer measurements. Accommodation on the ODEN for personnel to collect the tracer samples is being provided generously by Swedish colleagues. The proposed work will significantly enhance tracer studies in the Arctic Ocean by providing the first high-quality tracer data set from the poorly sampled Canadian Basin. They also will allow a look at decadal variability in the Eurasian Basin. Finally, the data will provide an extension of the global CLIVAR/carbon repeat hydrography program to the high northern latitude and will represent a firm baseline against which future sections can be compared to study possible anthropogenically driven change in the Arctic. The tracer data will be used to address the following scientific questions: (a) Determine freshwater distribution and inventories over the main basins of the Arctic Ocean and freshwater sources (meteoric water (river runoff and precipitation), sea ice meltwater and Bering Strait Inflow). (b) Explore changes in the freshwater inventory over the Nansen and Amundsen basins compared to those observed along sections occupied in 1991 and 1996 (decadal variability). (c) Determine circulation patterns of the upper waters (surface, halocline, and Atlantic-derived waters). (d) Examine mid-depth circulation patterns in the central Arctic Ocean. (e) Determine the mean residence times and age gradients in the deep waters in the Canadian Basin. The tracer data will be collected and interpreted in close cooperation with the other oceanographic programs on ODEN. The program addresses objectives of ARCSS, SEARCH, and ASOF, as well as high-latitude CLIVAR. Broader Impacts: The program will help to determine to which degree the wide range of changes that have recently been documented in the Arctic are part of natural variability or change due to human activities. This question has important societal relevance because a change towards a new state of the arctic system would have global ramifications for climate, as well as economy. Many indicators hint at the latter scenario, but we still lack the scientific certainty for an anthropogenically driven change of the arctic system. Additional broader impacts include the availability of high-quality data sets from the Arctic that will be used to assemble global data sets for climate and carbon studies (tracer measurements are an important element for estimating the amount of anthropogenic carbon in the ocean). On the educational side, the data will be available to students working on high latitude problems, and the results will be posted on a web site. The material is also routinely used in advanced courses taught at Columbia University. The material is typically used in case studies in courses on tracer oceanography or environmental tracer techniques. The data are also used by students for term papers or problem sets. Finally the PIs are establishing a program with high schools that will allow students to closely follow the evolution of scientific knowledge by involving them in each part of the proposed work.