The fate of freshwater in tidally stirred shelf seas

大陆架海区在河口和海洋之间提供了一个关键的界面，淡水、悬浮颗粒物质以及由此产生的碳、营养物质和人为污染物通过该界面进行交换。虽然大陆架海流主要由潮汐控制，但决定淡水长期命运的通常是弱得多的残余环流。因此，预测水在这些关键界面上的交换(及其负荷)的一个重要前提是确定和量化负责形成和控制剩余循环的过程和机制。经典观点认为，这种环流本质上是由密度驱动的，然而，最近的理论工作表明，层结水平和垂直混合率(称为潮汐应变)的“潮汐不对称”极大地增强了剩余环流。支持这一观点的轶事证据有限。我们还认为，最先进的三维流体动力学模型未能正确模拟这些地区的盐度(即淡水)分布，是因为它们未能正确模拟那里的潮汐应变机制。我们的建议是调查潮汐应变在确定陆架海淡水离岸通量方面的重要性。将通过识别和量化决定潮汐搅动陆架海淡水命运的关键过程来检验这一假说：在潮汐搅动的陆架海中，淡水的离岸通量在很大程度上是由潮汐应变决定的。为了实现这一目标，我们将使用海岸观测站的观测和最先进的数值模式预测。

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.