The Tropical Atlantic Ocean has recently been the source of enormous amounts of floating Sargassum macroalgae that have started to inundate shorelines in the Caribbean, the western coast of Africa and northern Brazil. It is still unclear, however, how the surface currents carry the Sargassum, largely restricted to the upper meter of the ocean, and whether observed surface drifter trajectories and hydrodynamical ocean models can be used to simulate its pathways. Here, we analyze a dataset of two types of surface drifters (38 in total), purposely deployed in the Tropical Atlantic Ocean in July, 2019. Twenty of the surface drifters were undrogued and reached only ∼8 cm into the water, while the other 18 were standard Surface Velocity Program (SVP) drifters that all had a drogue centered around 15 m depth. We show that the undrogued drifters separate more slowly than the drogued SVP drifters, likely because of the suppressed turbulence due to convergence in wind rows, which was stronger right at the surface than at 15 m depth. Undrogued drifters were also more likely to enter the Caribbean Sea. We also show that the novel Surface and Merged Ocean Currents (SMOC) product from the Copernicus Marine Environmental Service (CMEMS) does not clearly simulate one type of drifter better than the other, highlighting the need for further improvements in assimilated hydrodynamic models in the region, for a better understanding and forecasting of Sargassum drift in the Tropical Atlantic.

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热带大西洋表面漂流物的扩散

热带大西洋最近成为大量漂浮的马尾藻大型藻类的来源，这些大型藻类已经开始淹没加勒比海、非洲西海岸和巴西北部的海岸线。然而，目前仍不清楚表面流如何携带马尾藻，主要限于海洋的上米，以及是否可以使用观察到的表面漂移轨迹和水动力海洋模型来模拟其路径。在这里，我们分析了 2019 年 7 月特意部署在热带大西洋的两种类型的水面漂流器（共 38 个）的数据集。其中 20 个水面漂流器没有浸入水中，仅下水约 8 厘米，而另一个18 个是标准的表面速度程序 (SVP) 漂流器，它们都有一个以 15 m 深度为中心的锥套。我们表明，未垂流的漂流器比垂流过的 SVP 漂流器分离得更慢，这可能是因为风行会聚导致的湍流被抑制，这在地表比在 15 m 深度更强。未干涸的漂流者也更有可能进入加勒比海。我们还表明，哥白尼海洋环境服务中心 (CMEMS) 的新型表面和合并洋流 (SMOC) 产品并没有比另一种更好地模拟一种类型的漂流器，这突出表明需要进一步改进该地区的同化水动力模型，以便更好地了解和预测热带大西洋的马尾藻漂移。未干涸的漂流者也更有可能进入加勒比海。我们还表明，哥白尼海洋环境服务中心 (CMEMS) 的新型表面和合并洋流 (SMOC) 产品并没有比另一种更好地模拟一种类型的漂流器，这突出表明需要进一步改进该地区的同化水动力模型，以便更好地了解和预测热带大西洋的马尾藻漂移。未干涸的漂流者也更有可能进入加勒比海。我们还表明，哥白尼海洋环境服务中心 (CMEMS) 的新型表面和合并洋流 (SMOC) 产品并没有比另一种更好地模拟一种类型的漂流器，这突出表明需要进一步改进该地区的同化水动力模型，以便更好地了解和预测热带大西洋的马尾藻漂移。