Collaborative Research: Unraveling connectivity constraints and pathways of Sargassum and the nature of their variability by building on a Maxey-Riley framework for drift modeling

卫星图像显示，在墨西哥湾西北部的马尾藻海中有大量的浮游马尾藻，在过去十年中，还出现了一个新的经常性带状带，称为大大西洋马尾藻带，通常从非洲西海岸延伸到加勒比海。热带和亚热带大西洋中浮游马尾藻的数量是一种新形式的沿海灾害，直接影响到近岸生态系统的水质和海洋生物资源。该项目旨在开发和实施一个以新颖的方式对海洋和大气环流以及不断变化的环境条件作出反应的马尾藻物理-生物运输模型。该模型将考虑海流和风阻力的综合影响，并由马尾藻筏惯性介导，这将是一个生长和死亡率的函数，以响应环境温度和营养物质的可用性。本项目将使用基于第一原理的Maxey-Riley框架的流体力学的惯性粒子运动的研究，发展一个框架来模拟马尾藻漂移。研究人员已经扩展并测试了这一应用，以研究漂浮在海洋表面的孤立物体的漂移。这个基础，并进一步最近的理论发展，将有助于建立一个机械的物理生理模型制定的海藻筏表示为网络的弹性相互作用的浮动惯性粒子的配置变化，根据增长模型的运动。在模型中，这些马尾藻筏大小和形状的变化将相应地影响它们的运输。进行拟议的马尾藻连通性调查所需的载流将从再分析系统和多数据合成中获得。海藻运输模型将通过卫星跟踪部署在佛罗里达海流的海藻筏进行实地测试。将在空气-水水槽设施中进行实验室实验，以量化浮力相关的偏航和限制波浪诱导的漂移效应。连通性分析和不确定性量化的工具将来自遍历非线性动力学理论，包括用于构建渐近几乎不变集的面向集合的方法和离散马尔可夫链的转移路径理论。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Satellite imagery has revealed abundant pelagic Sargassum seaweed in the Sargasso Sea, the northwestern Gulf of Mexico and, in the last decade, a new recurrent zonal band, referred to as the Great Atlantic Sargassum Belt (GASB), often extending from the west coast of Africa to the Caribbean Sea. The magnitude of pelagic Sargassum in the tropical and subtropical Atlantic represents a new form of coastal hazard with direct impact on the water quality and living marine resources of the nearshore ecosystem. This project seeks to develop and implement a physical-biological transport model of Sargassum responding in a novel manner to the ocean and atmospheric circulations and changing environmental conditions. The model will account for the combined effects of ocean currents and wind drag mediated by Sargassum raft inertia, which will be a function of growth and mortality in response to ambient temperature and nutrient availability.This project would use first-principle-based Maxey–Riley framework of fluid mechanics for the study of inertial particle motion to develop a framework for modeling Sargassum drift. The investigators have extended and tested this application to investigating the drift of isolated objects floating at the ocean surface. This foundation, and further recent theoretical developments, will contribute to building a mechanistic physical–physiological model formulation for the movement of Sargassum rafts represented as networks of elastically interacting floating inertial particles whose configurations change according to a growth model. In the model, these changes in Sargassum raft size and shape will correspondingly affect their transport. The required carrying flow to conduct the proposed Sargassum connectivity investigation will be obtained from reanalysis systems and a multidata synthesis. The Sargassum transport model will be tested in the field by satellite tracking Sargassum rafts deployed in the Florida Current. Laboratory experiments in an air-water flume facility will be carried out to quantify buoyancy dependent leeway and constrain wave-induced drift effects. Tools for connectivity analysis and uncertainty quantification will be brought from ergodic nonlinear dynamics theory including set-oriented methods for framing asymptotically almost-invariant sets and the transition path theory for discrete Markov chains.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.