Collaborative Research: Constraining Water Mass Age and Particle Flux in the Arctic Ocean Using Pa-231 and Th-230 as Tracers

摘要OPP-0002313 MoranOPP-0004029爱德华这是罗德岛大学和明尼苏达双城大学的首席研究人员共同提出的建议。北冰洋的动态比以前认为的要大得多，其特点是生产力和相关颗粒通量的空间和季节变化很大，显著的河口输入和延伸到内陆盆地的陆架水的横向入侵，以及沿盆地周围的地形控制的边界流，导致区域水团年龄的极端。首席调查人员假设，由横向平流和颗粒通量共同控制的“边界清除”在清除北冰洋水柱中的颗粒活性化学物质方面发挥着重要作用。他们将评估边界清理的作用，因为它对碳向深水出口、包括污染物在内的活性化学品的沉积物积累以及向大西洋出口这些化学品等关键的地球化学过程具有重要影响。其目标是在整个盆地范围内限制这些基本过程，并为这种知之甚少的极端环境开发可预测的生物地球化学模型。首席调查员将确定该天然放射性核素-231(231Pa)-Th-230(231Th)对是否可以用作示踪剂，以提供现代和最后一次冰川弧盆地范围内水团年龄和颗粒通量的综合图像。为了加深对控制这些示踪剂在北冰洋重新分布的过程的了解，首席调查员将进行一项全面的研究，包括对水柱、沉积物圈闭材料、表层沉积物和沉积物中溶解和颗粒样品的231Pa231Th分析。这将有助于通过量化悬浮颗粒物、沉积物捕集器物质和表层沉积物的化学成分，更好地了解颗粒组成在231Pa231Th分馏中的重要性。在北极，由于陆架与开阔海洋的高比例、水质量年龄和颗粒通量的区域极值以及动态环流的综合作用，北极应该有明显的边界清理。这一环境背景明显不同于已经进行了Pa和Th示踪研究的其他海洋区域，为研究边界清除提供了独特的机会，进而制约了关于231Pa231Th古应用的一些悬而未决的问题。

Abstract OPP-0002313MoranOPP-0004029EdwardsThis is a collaborative proposal between Principal Investigators at the Universities of Rhode Island and Minnesota-Twin Cities. The Arctic Ocean is much more dynamic than previously believed, characterized by large spatial and seasonal variations in productivity and associated particle flux, significant estuarine input and lateral intrusions of shelf water extending into the interior basins, and topographically-steered boundary currents along the perimeters of basins that result in regional extremes in water mass age. The Principal Investigators hypothesize that "boundary scavenging", controlled by a combination of lateral advection and particle flux, plays a significant role in the removal of particle-reactive chemicals from the water column of the Arctic Ocean. They will evaluate the role of boundary scavenging as it has an important bearing on such key geochemical processes such as the export of carbon to deep waters, the sediment accumulation of reactive chemicals, including contaminants, and the export of these chemicals to the Atlantic. The objective is to constrain these fundamental processes on a basin-wide scale and to develop predictive biogeochemical models for this poorly understood and extreme environment. The Principal Investigators will determine whether that natural radionuclide Protactinium-231 (231Pa) - Thorium -230 (231Th) pair can be used as tracers to provide an integrated picture of water mass age and particle flux on a basin-wide scale in the modem and last glacial Arctic.To provide an increased understanding of the processes that control the redistribution of these tracers in the Arctic Ocean, the Principal Investigators will undertake a comprehensive study that includes paired 231Pa - 231Th analyses in dissolved and particulate samples from the water column, sediment trap material, surface sediments and sediment comes. This should help with a better understanding of the importance of particle composition on 231Pa - 231Th fractionation by quantifying the chemical composition of suspended particulate matter, sediment trap material and surface sediments. Boundary scavenging should be pronounced in the Arctic, due to the combined effects of the high ratio of shelf to open ocean, the regional extremes in water mass age and particle flux, and a dynamic circulation. This environmental setting is markedly different than other ocean regions where Pa and Th tracer studies have been conducted and provides a unique opportunity to investigate boundary scavenging and, in turn, constrain some outstanding questions regarding the paleo-application of 231Pa - 231Th.