Cold fronts control multiscale spatiotemporal hydroperiod patterns in a man-made subtropical coastal delta (Wax Lake Region, Louisiana USA)

IF 2.2 3区 地球科学 Q2 OCEANOGRAPHY Ocean Dynamics Pub Date : 2024-03-14 DOI:10.1007/s10236-024-01608-9
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引用次数: 0

Abstract

Atmospheric cold fronts quasi-periodically produce storm surges and generate significant subtidal oscillations of water levels and water transport in coastal environments. Yet, it is unclear how these weather events—at regional scales —control the hydrodynamics in delta-dominated coasts. Here, we used a numerical model (SCHISM) to simulate the inundation/drying and water circulations generated by varying winds associated with cold front passages across the Atchafalaya Bay in the northern Gulf of Mexico, specifically the Wax Lake Delta (WLD) region. Water transport induced by winds through major channels of the WLD and that between the adjacent Vermilion Bay and inner shelf were quantified to evaluate the impact of cold fronts. Results show that significant wetting/drying conditions are highly correlated with wind direction and strength. Southerly/easterly winds tend to cause water set-up, thus inundating the delta region, while northerly and westerly winds cause water set-down, draining the bay into the continental shelf. As a result, up to 60% of the delta area (~ 50 km2) can become exposed land under northerly winds. The interconnectivity of the delta channel system is also highly dependent on the wind direction and magnitude: up to 37% of the total transport is through the shallow waters outside of the channels during cold fronts. In contrast, the water levels and velocity variations in the delta region were negatively correlated with the alongshore wind, a result of Ekman transport. At the delta head, where freshwater flows like a strong jet into the region, the velocity is marginally correlated with the wind but mostly correlated with seasonal river discharge variability of river discharge. At the transitional zone between the bay and coastal ocean, water level and surface flows are dominated by tidal forcing in contrast to the delta lobes area where wind regulates the flooding area extension. The bottom velocity and water levels at sites along the Atchafalaya Bay mouth negatively correlate with onshore wind, indicating bottom return flows against the wind. Our study offers a glimpse of how a combination of atmospheric and hydrodynamic forces operate in a young delta, where the coast is experiencing the highest sea level rise in North America.

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冷锋控制人造亚热带沿海三角洲(美国路易斯安那州瓦克斯湖地区)的多尺度时空水文周期模式
摘要 大气冷锋准周期性地产生风暴潮,并对沿岸环境的水位和水流产生显著的潮下振动。然而,目前还不清楚这些天气事件在区域尺度上是如何控制以三角洲为主的海岸的水动力的。在此,我们使用一个数值模型(SCHISM)模拟了墨西哥湾北部阿查法拉亚湾,特别是瓦克斯湖三角洲(WLD)地区与冷锋过境相关的变化风所产生的淹没/干燥和水循环。为评估冷锋的影响,对通过 WLD 主要通道的风引起的水流输送以及邻近的朱砂湾和内陆架之间的水流输送进行了量化。结果表明,重要的湿润/干燥条件与风向和风力高度相关。南风/东风往往会导致水位上升,从而淹没三角洲地区,而北风和西风则会导致水位下降,将海湾的水排入大陆架。因此,在北风的作用下,多达 60% 的三角洲区域(约 50 平方公里)会成为裸露的陆地。三角洲水道系统的相互连接也与风向和风力大小有很大关系:在冷锋期间,高达 37% 的总输送量是通过水道外的浅水区进行的。相反,三角洲地区的水位和流速变化与沿岸风向呈负相关,这是埃克曼输送的结果。在三角洲头,淡水像一股强大的喷流流入该区域,流速与风的相关性较小,但主要与河流排泄量的季节性变化相关。在海湾和沿岸海洋之间的过渡区,水位和表层流主要受潮汐作用的影响,而在三角洲裂片区,风力对洪泛区的扩展起着调节作用。阿查法拉亚湾湾口沿岸的底层流速和水位与陆上风力呈负相关,表明底层回流与风力相反。我们的研究让人们看到了大气和流体动力如何在年轻的三角洲中共同作用,而这里的海岸正经历着北美最高的海平面上升。
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来源期刊
Ocean Dynamics
Ocean Dynamics 地学-海洋学
CiteScore
5.40
自引率
0.00%
发文量
37
审稿时长
6-12 weeks
期刊介绍: Ocean Dynamics is an international journal that aims to publish high-quality peer-reviewed articles in the following areas of research: Theoretical oceanography (new theoretical concepts that further system understanding with a strong view to applicability for operational or monitoring purposes); Computational oceanography (all aspects of ocean modeling and data analysis); Observational oceanography (new techniques or systematic approaches in measuring oceanic variables, including all aspects of monitoring the state of the ocean); Articles with an interdisciplinary character that encompass research in the fields of biological, chemical and physical oceanography are especially encouraged.
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