Collaborative Research: The Influence of the Mendeleev Ridge and the Chukchi Borderland on the Large-scale Circulation of the Arctic Ocean

合作研究：门捷列夫海岭和楚科奇边境对北冰洋大范围环流的影响

• 批准号: 0118034
• 负责人: James Swift
• 金额: --
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0118034&HistoricalAwards=false
• 关键词: Collaborative; Research; Influence; Mendeleev; Ridge

The most important subsurface Arctic Ocean transport system, a cyclonic (here anticlockwise) boundary current, organized along the continental slopes and major trans-Arctic ridges, distributes waters, tracers and contaminants from the Atlantic (via Fram Strait and the Barents Sea) and the Pacific (via Bering Strait) around and into the deep Arctic basins. On its circum-Arctic pathway, parts of the topographically steered current are diverted away from the continental margin, generally along topographic ridges. The most complex obstacle the boundary current encounters is the Mendeleev Ridge/Chukchi Borderland complex, north of the Pacific entrance to the Arctic. This region is the cross- roads for Pacific-origin waters from the south and Atlantic waters carried from the west with the boundary current. The tortuous bathymetry offers many routes for a topographically steered current, and the spatial variability of the sparse data that exist clearly indicates the complexity of the region. These data also show significant interannual variability, in line with the major changes seen in the last decade throughout the Arctic, and they further suggest that the region diverts significant amounts of water into the deep basins, indicating this region's importance to shelf-basin exchange, deep basin ventilation, and circum- and trans-Arctic circulation (with feedback implications to the World Ocean circulation). Yet, the pathways and exchanges in this area are still unclear, both qualitatively and quantitatively, due to the lack of sufficiently concentrated observations. This research will conduct a high spatial resolution hydrographic and tracer survey, supported by short-term moored current and CTD measurements, in the region of the Chukchi Borderland and the southern end of the Mendeleev Ridge during August/September 2002.The objectives are to:- delineate the pathways of the boundary current carrying the Atlantic water past the Mendeleev Ridge and through the Chukchi Borderland;- ascertain the input from the boundary current and the shelves to the deep Arctic Ocean in the vicinity of the Mendeleev Ridge and the Chukchi Borderland;- understand and quantify the pathways and transformations of the Pacific waters through this region;- describe the horizontal and vertical structure of the boundary current, and estimate its transport; and- quantify recent temporal changes in this region by combining the spatially sparse data extending through most of the past decade with new detailed synoptic measurements.On a 35-day expedition on an ice-breaking research vessel, measurements will be made of temperature, salinity, dissolved oxygen, nutrients, CFCs, Ba, and 18-O on 12 sections that cross both the boundary flow and the Pacific inputs to the region before and after topographic junctions and hypothesized regions of flow diversion. This tracer suite will enable identification of the pathways of the boundary current and the Pacific-origin waters, and quantification of the different Atlantic and Pacific influences, as well as freshwater input from ice melt and different rivers. In addition, three moorings will be deployed, spanning the boundary current for the duration of the cruise. Current meters and moored conductivity and temperature sensors will quantify the vertical and horizontal extent of the boundary current, its structure and variability, and will yield an estimate of the transport and a description of eddies carried with or across the boundary current. To give a comprehensive picture of the system, the entire data set will be analyzed collectively and in tandem with hydrographic, tracer, and moored time series data from the last decade. Since the transit time of signals through this region is 2-4 years, the older data provide a temporal background for the new high spatial resolution data, whilst the newer data will supply an essential spatialframework for understanding the variability of the older surveys.The work will yield a substantially increased understanding of the role of this region in the Arctic circulation, including a determination of pathways, a quantification of exchanges, and an assessment of temporal change. Its timing in 2002 will fill a pending hiatus in hydrographic surveys in the Canadian Basin at a time when the most dramatic changes ever observed in the Arctic are propagating through this region. The project will provide necessary background and mechanistic information to the potential SEARCH and Arctic-Subarctic Ocean Flux programs, and essential far-field information to the SBI Phase II field program in the Chukchi and Beaufort seas. In addition, the results will be pivotal to validating and improving high resolution computer and conceptual models of the Arctic, and will offer insights to physical mechanistic problems, such as the driving mechanism of the boundary current and the interaction of an equivalent barotropic current with steep and sharp topography.

最重要的北冰洋次表层输运系统是一个气旋性（此处为反气旋性）边界流，它沿着大陆坡和主要的跨北极海脊排列，将来自大西洋（通过弗拉姆海峡和巴伦支海）和太平洋（通过白令海峡）的沃茨、示踪剂和污染物分布在北极深海盆周围并流入北极深海盆。在其环北极路径上，部分受地形控制的海流转向远离大陆边，一般是沿沿着地形脊转向。边界电流遇到的最复杂的障碍是门捷列夫海岭/楚科奇边界复合体，位于太平洋北极入口以北。这一区域是边界流从南部输入的太平洋沃茨和从西部输入的大西洋沃茨的交汇点。曲折的水深测量为地形导向的海流提供了许多路线，现有稀疏数据的空间变异性清楚地表明了该区域的复杂性。这些数据还显示了显著的年际变化，与整个北极过去十年中的主要变化一致，它们进一步表明，该地区将大量的水转移到深海盆地，表明该地区对陆架盆地交换、深海盆地通风以及环北极和跨北极环流的重要性（对世界海洋环流具有反馈影响）。然而，由于缺乏足够集中的观测，这一领域的路径和交流在质量和数量上都还不清楚。这项研究将于2002年8月/9月在楚科奇边界地区和门捷列夫海脊南端进行高空间分辨率水文和示踪调查，并辅以短期系泊海流和CTD测量。- 确定门捷列夫海岭和楚科奇边界附近的边界流和冰架对北冰洋深海的影响;-了解太平洋沃茨通过这一区域的路径和变化并加以量化;- 描述边界流的水平和垂直结构，并估计其输送;并通过将过去十年大部分时间的空间稀疏数据与新的详细天气测量相结合，量化该地区最近的时间变化。在一艘破冰研究船上进行的为期35天的考察中，将对12个断面的温度、盐度、溶解氧、营养物、CFC、Ba和18-O进行测量，这些断面在地形交汇点和假设的水流转向区域之前和之后穿过边界流和太平洋输入到该区域。这套示踪剂将能够确定边界流和太平洋起源沃茨的路径，并量化大西洋和太平洋的不同影响，以及来自冰融化和不同河流的淡水输入。此外，将部署三个系泊系统，在巡航期间跨越边界流。海流计和系泊的电导率和温度传感器将量化边界流的垂直和水平范围、其结构和可变性，并将产生对边界流携带或跨越边界流的输送的估计和对涡流的描述。为了全面了解该系统，将对整个数据集进行集体分析，并与过去十年的水文、示踪剂和系泊时间序列数据相结合。由于信号通过该区域的时间是2-4年，较旧的数据为新的高空间分辨率数据提供了时间背景，而较新的数据将为理解较旧的调查的变化提供一个基本的空间框架。这项工作将大大增加对该区域在北极环流中的作用的理解，包括确定路径，对交换进行量化，并对时间变化进行评估。2002年的时间安排将填补加拿大海盆水文测量的一个悬而未决的空白，而此时北极地区所观察到的最剧烈的变化正在向该地区蔓延。该项目将为潜在的北极和北极-亚北极海洋通量方案提供必要的背景和机制信息，并为楚科奇海和博福特海的SBI第二阶段实地方案提供必要的远场信息。此外，结果将是关键的验证和改进高分辨率的计算机和概念模型的北极，并将提供洞察力的物理机制问题，如边界流的驱动机制和相互作用的等效正压流与陡峭和尖锐的地形。