Investigation of the Rate of Shelf-Basin Interaction in the Western Arctic Using Radium Isotopes: SBI Phase II

以内陆为主的北冰洋接受来自太平洋和大西洋以及排干周围大陆的河流的输入。这些流入是中央盆地盐分、热量、营养物质、沉积物和生物的重要来源。除了大西洋贡献的一部分外，这些输入必须跨越大陆架，在那里它们受到海底、水柱和空气-冰-海洋相互作用的显著改变。作为跨陆架运输的结果，陆架和中央盆地之间存在着显著的生物地球化学交换。然而，我们目前缺乏量化这些交流的信息。为了解决这一不足，作为西部北极陆架-盆地相互作用第二阶段方案的一部分，该项目提议应用同位素水团示踪技术来评估西部北冰洋陆架和北冰洋内陆盆地之间的交换路径和速率。这项拟议的技术使用了两种天然存在的放射性同位素228Ra和226Ra在水柱中的测量浓度。由于228Ra的半衰期为5.77年，完全来自陆架沉积物，它为陆架水的存在提供了明确的证据。因此，它在陆架和盆地水中的相对浓度可以提供关于陆架-盆地水输送的定量信息。该技术已比较成熟，并已在其他地区陆架盆地交换研究中得到应用。在履行机构第一阶段方案期间开展的一个试点研究项目的结果表明，这项示踪技术在北冰洋西部具有实用价值。对于拟议的研究，将在近岸和近海实地研究和侧重于了解跨陆架运输的模拟研究的背景下，分析从穿过研究区域的横断面收集的示踪剂数据。重点将放在中尺度涡旋在这一输送中的作用。在适当的情况下，将在海上测量寿命较短、半衰期为3.64天的224Ra，以补充数据集。此外，还将尽可能从其他平台收集镭示踪剂数据，例如由履行机构其他调查员提供的系泊阵列。

The largely landlocked Arctic Ocean receives input from the Pacific and Atlantic Ocean and from rivers draining the surrounding continents. These inflows are important sources of salt, heat, nutrients, sediment and organisms for the central basin. With the exception of a portion of the Atlantic Ocean contribution, these inputs must cross continental shelves where they are modified significantly by benthic, water column, and air-ice-ocean interactions. As a consequence of the cross-shelf transports, there are significant biogeochemical exchanges between the shelves and the central basin. However, we currently lack the information to quantify these exchanges. In order to address this lack, this project proposes as part of the western Arctic Shelf-Basin Interaction (SBI) Phase II program to apply an isotopic water mass tracer technique to assess the pathways and rates of exchange between the western Arctic shelves and the interior Arctic Ocean basin. The proposed technique uses the measured concentrations in the water column of the two naturally occurring radioisotopes 228Ra and 226Ra. Because 228Ra, which has a half life of 5.77 years, is derived solely from shelf sediments, it provides unambiguous evidence of the presence of shelf water. Its relative concentration in shelf and basin waters can therefore provide quantitative information on shelf-basin water transports. This technique is mature and has been used in shelf-basin exchange investigations in other regions. Results of a pilot research project carried out during the SBI Phase I program have demonstrated utility of this tracer technique in the western Arctic Ocean. For the proposed research, tracer data collected from vessels along transects through the study region will be analyzed within the context of nearshore and offshore field and modeling studies that focus on understanding cross-shelf transport. An emphasis will be placed on the role of mesoscale eddies in this transport. Where appropriate, the shorter-lived 224Ra with its 3.64-day half life will be measured at sea to supplement the dataset. Radium tracer data will also be collected whenever possible from other platforms such as moored arrays provided by other SBI investigators.