A unique combination of data collected from fixed instruments, spatial surveys, and a long-term observing network in the Hudson River demonstrate the importance of spatial and temporal variations in atmospheric gas flux. The atmospheric exchanges of oxygen (O₂) and carbon dioxide (CO₂) exhibit variability at a range of time scales including pronounced modulation driven by spring-neap variations in stratification and mixing. During weak neap tides, bottom waters become enriched in pCO₂ and depleted in dissolved oxygen because strong stratification limits vertical mixing and isolates sub-pycnocline water from atmospheric exchange. Estuarine circulation also is enhanced during neap tides so that bottom waters, and their associated dissolved gases, are transported up-estuary. Strong mixing during spring tides effectively ventilates bottom waters resulting in enhanced CO₂ evasion and O₂ invasion. The spring-neap modulation in the estuarine portion of the Hudson River is enhanced because fortnightly variations in mixing have a strong influence on phytoplankton dynamics, allowing strong blooms to occur during weak neap tides. During blooms, periods of CO₂ invasion and O₂ evasion occur over much of the lower stratified estuary. The along-estuary distribution of stratification, which decreases up-estuary, favors enhanced gas exchange near the limit of salt, where vertical stratification is absent. This region, which we call the estuarine gas exchange maximum (EGM), results from the convergence in bottom transport and is analogous to the estuarine turbidity maximum (ETM). Much like the ETM, the EGM is likely to be a common feature in many partially mixed and stratified estuarine systems.

中文翻译：

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哈德逊河大气气体通量的时空变化：河口气体交换最大值

从哈德逊河的固定仪器、空间调查和长期观测网络收集的数据的独特组合证明了大气气体通量空间和时间变化的重要性。氧气 (O ₂ ) 和二氧化碳 (CO ₂ ) 的大气交换在一系列时间尺度上表现出可变性，包括由分层和混合中的春季小睡变化驱动的显着调制。在弱小潮期间，底水富含 pCO ₂并耗尽溶解氧，因为强烈的分层限制了垂直混合并将亚重跃层水与大气交换隔离开来。在小潮期间，河口环流也得到加强，因此底水及其相关的溶解气体被输送到河口上游。大潮期间的强烈混合有效地使底水通风，从而增强了CO ₂逃逸和O ₂入侵。哈德逊河河口部分的春季小潮调节得到了加强，因为每两周混合的变化对浮游植物动态有很大的影响，允许在弱小潮期间发生强烈的水华。在开花期间，CO ₂入侵和 O _{2入侵期间}逃逸发生在下层河口的大部分地区。沿河口的分层分布，在河口上游减少，有利于在没有垂直分层的盐限附近加强气体交换。这个区域，我们称之为河口气体交换最大值（EGM），是由底部传输的收敛产生的，类似于河口浊度最大值（ETM）。与 ETM 非常相似，EGM 可能是许多部分混合和分层的河口系统的共同特征。