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，马尾藻海和墨西哥湾西北部有丰富的浮游性马尾藻海藻，在过去十年中，一个新的经常性纬向带，称为大大西洋马尾藻带(GASB)，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上层马尾藻的数量是一种新的沿海灾害形式，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马尾藻的物理-生物运输模型，以一种新的方式对海洋和大气循环和不断变化的环境条件作出反应。该模型将考虑海流和由马尾藻木筏惯性传递的风阻力的综合影响，该惯性将是环境温度和营养物质可获得性的生长和死亡的函数。本项目将使用基于第一原理的流体力学的Maxey-Riley框架来研究惯性粒子运动，以开发一个框架来模拟马尾藻漂移。研究人员将这一应用扩展并测试到调查漂浮在海洋表面的孤立物体的漂移。这一基础，以及最近的进一步理论发展，将有助于建立马尾藻木筏运动的机械物理-生理模型公式，该模型表示为弹性相互作用的浮动惯性粒子网络，其形状根据生长模型而改变。在模型中，马尾藻筏大小和形状的这些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携带流量将从再分析系统和多数据合成中获得。马尾藻运输模型将通过卫星跟踪部署在佛罗里达洋流中的马尾藻木筏在现场进行测试。将在空气-水水槽设施中进行实验室实验，以量化浮力相关的回旋余地，并限制波浪引起的漂移效应。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智力优势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.