Selecting and Applying an Inverse Method to Infer Particle Dynamics from GEOTRACES Data

影响海洋粒子的过程对海洋微量元素的生物地球化学循环具有重要影响；然而，我们目前对这些过程的理解是不完整的，正如目前对海洋中粒子循环速率的估计存在很大的不确定性（跨越数量级）所表明的那样。作为GEOTRACES项目的一部分，广泛的微量元素数据集提供了一个机会来增强我们对各种海洋环境中粒子过程的了解。伍兹霍尔海洋研究所的一名科学家计划通过测量钍同位素活度、颗粒组成和不同大小馏分的颗粒浓度，来确定不同的反方法是否足够，以约束颗粒过程，如固溶交换和水柱中的颗粒过程。为了实现这一目标，研究人员将首先评估不同逆方法的充分性，以从这样一个折衷的数据集推断吸附反应（吸附和解吸）的速率常数和颗粒动力学（聚集、分解、下沉和再矿化）。第二步将涉及应用选定的方法在GEOTRACES北大西洋纬向剖面的“超级站”估计这些常数及其不确定性。一旦模型到位，科学家将测试速率常数变化的假设：(1)在这些站点的中层和深层内垂直变化，(2)在沿着剖面采样的不同环境中水平变化。更广泛的影响：要开发的软件将被生物和化学海洋学数据管理办公室存档，并附有说明，以便其他科学家使用。一名研究生将接受关于在数据分析中使用逆方法的培训。

Processes affecting ocean particles have important consequences for the marine biogeochemical cycles of trace elements; however, our present understanding of these processes is incomplete, as shown by the very large uncertainties (spanning orders of magnitude) of current estimates of particle cycling rates in the ocean. The extensive trace element dataset being generated as part of the GEOTRACES program provides an opportunity to enhance our knowledge of particle processes in a variety of oceanic environments. A scientist from Woods Hole Oceanographic Institution plans to determine the adequacy of different inverse methods to constrain particle processes such as solid-solution exchange and particle processes in the water column from measurements of thorium isotope activity, particle composition, and particle concentration in different size fractions. To attain this goal, the researcher would first assess the adequacy of different inverse methods to infer, from such an eclectic dataset, rate constants of sorption reactions (adsorption and desorption) and particle dynamics (aggregation, disaggregation, sinking, and remineralization). The second step would involve applying the selected method to estimate these constants and their uncertainties at the "superstations" of the GEOTRACES North Atlantic Zonal Section. Once the model is in place, the scientist would test the hypotheses that the rate constants varied (1) vertically within the mesopelagic layer and the deeper layers at these stations and (2) horizontally across the diverse environments sampled along the section.Broader Impacts: The software to be developed would be archived with the Biological and Chemical Oceanography Data Management Office with instructions so other scientist can use it. One graduate student would be trained on the use of inverse methods in data analyses.