The fate of freshwater in tidally stirred shelf seas

大陆架海域是河口与海洋之间的一个重要界面，淡水、悬浮颗粒物以及碳、营养物和人为污染物通过该界面进行交换。虽然大陆架海域的洋流主要由潮汐控制，但通常是弱得多的残余环流决定了淡水的长期命运。因此，预测这些关键界面上的水（及其负荷）交换的一个重要先决条件是识别和量化负责剩余循环的形成和控制的过程和机制。经典的观点是，这种环流基本上是密度驱动的，然而最近的理论工作表明，在分层和垂直混合率（称为潮汐应变）的水平的“潮汐不对称”大大增强了剩余环流。支持这一观点的轶事证据有限。我们还认为，最先进的三维水动力学模型未能再现这些地区盐度（即淡水）的正确分布，是由于它们未能正确模拟潮汐应变机制。我们的建议是调查的重要性，潮汐应变在确定近海通量的淡水在陆架海。通过识别和量化确定潮汐搅动陆架海淡水命运的关键过程，将检验“潮汐搅动陆架海淡水离岸通量主要由潮汐应变决定”的假设。为了实现这一目标，我们将使用沿海观测站观测和最先进的数值模型预测。

Regions of continental shelf seas provide a critical interface between estuaries and the ocean across which freshwater, suspended particulate matter, and consequently carbon, nutrients and anthropogenic contaminants are exchanged. Whilst the currents in continental shelf seas are dominated by the tide, it is the normally much weaker, residual circulation which determines the longer term fate of the freshwater. A vital prerequisite to the prediction of the exchange of water (and its load) across these critical interfaces is therefore the identification and quantification of the processes and mechanisms which are responsible for the formation and control of the residual circulation. The classical view is that this circulation is essentially density driven, however recent theoretical work has suggested that a 'tidal asymmetry' in both the level of stratification and the vertical mixing rate (known as tidal straining) greatly enhance the residual circulation. There is limited anecdotal evidence to support this idea. We would also suggest that the failure of state-of-the-art 3-dimensional hydrodynamic models to reproduce the correct distribution of salinity (i.e. freshwater) in these regions is a result of their failure to correctly simulate there tidal straining mechanism. Our proposal is to investigate the importance of tidal straining in determining the off-shore flux of freshwater in shelf seas. The hypothesis 'the off-shore flux of freshwater in tidally stirred shelf seas is largely determined by tidal straining' will be tested through identification and quantification the key processes which determine the fate of freshwater in tidally stirred shelf seas. To acheive this aim we will use coastal observatory observations and state-of-the-art numerical model predictions.