Abstract River plume source-front connectivity, or the relationship between processes at the source, plume body and front, is investigated with numerical simulations of the Merrimack River plume using the Regional Ocean modeling System (ROMS). Source water, i.e. water discharged from the estuary during an ebb pulse, overtakes the front as it propagates offshore, resulting in the strong convergence that exists there. Model results show that much of the water released over an ebb pulse does not interact with the propagating tidal plume front, suggesting that the front decouples from the source and sustains itself as a distinct water mass. When a gate is closed at the estuary mouth during early ebb, the overall plume structure changes; gates closed late in ebb do not significantly effect the along- or cross-shore scale of the plume. The change in plume extent is only evident hours after the early-ebb gate closing, when source water is no longer supplied to the front. These experiments suggest that the growing distance between the highly energetic liftoff region and the radial expansion of the plume front results in a flattening of the surface gradient driving flow in the interior, diminishing source-front connectivity.

中文翻译：

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河羽源-锋连通性

摘要 通过使用区域海洋建模系统 (ROMS) 的梅里马克河羽流的数值模拟，研究了河流羽流源-锋的连通性，或源、羽体和前沿过程之间的关系。源水，即在退潮期间从河口排出的水，在向近海传播时超过了锋面，导致那里存在强烈的辐合。模型结果表明，在落潮脉冲上释放的大部分水不会与传播的潮汐羽流前缘相互作用，这表明前缘与源头分离并以独特的水团形式维持自身。早退时河口关闭闸门，整体羽流结构发生变化；在退潮后期关闭的闸门不会显着影响羽流的沿海岸或跨海岸规模。羽流范围的变化仅在早期退潮闸门关闭数小时后才明显，此时源水不再供应到前沿。这些实验表明，高能升空区域和羽流锋的径向扩张之间的距离越来越大，导致内部表面梯度驱动流变平，减少了源-锋的连通性。