Collaborative Research: Understanding the Distribution and Stable-Isotopic Composition of Planktonic Foraminifera in the Western Arctic Ocean

对北冰洋西部浮游有孔虫分布及其稳定同位素组成的认识不足，是我们重建北冰洋西部古气候历史的一个重大缺陷。本提案旨在深入研究北冰洋楚科奇/阿拉斯加地区水柱和海底表层沉积物中的浮游有孔虫和稳定同位素。该地区的特点是受北极和太平洋水域以及冰边缘过程的相互作用影响的动态水文系统。需要了解这一系统的演变是由于现代冰盖的急剧减少造成的，这种减少影响到该区域内外海洋和沿海环境的许多方面。浮游有孔虫将在特定深度的浮游生物拖曳中进行研究。调查将包括(1)鉴定和计数活的有孔虫，并在63米开始的几个尺寸部分进行空测试，(2)测量来自各自亚样品的有孔虫方解石中碳和氧的稳定同位素，以及(3)测量环境水中的稳定同位素。本研究将以2002-2004年NSF陆架-盆地相互作用（SBI）项目收集的海底表层沉积物样品中浮游有孔虫及其稳定同位素组成的类似调查作为补充。由SBI收集和/或汇编的广泛的水文、水化学、生物和冰数据将有助于对结果的解释。这项研究的结果将使浮游有孔虫及其稳定的同位素特征成为北冰洋西部水文和冰况的古海洋学代用物。本研究的具体目标将集中在了解楚科奇/阿拉斯加地区水柱中有孔虫和稳定同位素分布的水文和水化学控制以及海底沉积物各自的空间格局。这些结果除了对北极西部的古气候研究具有重要意义外，还将提高我们对低温海洋环境中生物介导的钙化过程的基础知识。这项研究的社会意义源于需要全面评估现代气候变化对楚科奇/阿拉斯加地区的潜在影响，这具有许多社会经济方面。该项目的工作将包括培训两所大学的研究生和几名本科生。

The deficiency of knowledge on the distribution of planktonic foraminifers and their stable-isotopic compositions in the western Arctic Ocean constitutes a significant shortcoming in our capabilities to reconstruct its paleoclimatic history. This proposal aims at an in-depth investigation of planktonic foraminifers and stable isotopes in the water column and seafloor surface sediments in the Chukchi/Alaskan region of the Arctic Ocean. This area is characterized by a dynamic hydrographic system affected by the interaction of Arctic and Pacific waters and ice marginal processes. The need for understanding the evolution of this system is caused by dramatic modern reduction in ice cover that affects many aspects of marine and coastal environments in and far beyond the region. Planktonic foraminifers will be investigated in depth-specific plankton tow. The investigation will include (1) identification and counts of live foraminifers and empty tests in several size fractions starting at 63 m, (2) measurements of stable isotopes of carbon and oxygen in foraminiferal calcite from respective subsamples, and (3) stable-isotopic measurements in ambient water. This study will be supplemented by the similar investigation of planktonic foraminifers and their stable-isotopic compositions in seafloor surface sediment samples collected by the NSF Shelf-Basin Interaction (SBI) Program in 2002-2004. Interpretation of results will be facilitated by the extensive hydrographic, hydrochemical, biological, and ice data collected and/or compiled by the SBI. Results of this study will enable the use of planktonic foraminifers and their stableisotopic signatures as paleoceanographic proxies for hydrographic and ice conditions in the western Arctic Ocean. Specific objectives of this research will focus on understanding hydrographic and hydrochemical controls on the distribution of foraminifers and stable isotopes in the water column as well as respective spatial patterns in seafloor sediments across the Chukchi/Alaskan region. In addition to the importance of these results for paleoclimatic research in the western Arctic, they will also improve our fundamental knowledge of biologically-mediated calcification processes in low-temperature marine environments. The societal significance of this research stems from the need for a comprehensive evaluation of the potential effects of modern climatic change on the Chukchi/Alaskan region that has many socio-economical aspects. Work on the project will involve training of graduate and several undergraduate students in two universities.