The fate of freshwater in tidally stirred shelf seas

潮汐搅动的陆架海中淡水的命运

• 批准号: NE/D012023/1
• 负责人: Tom Rippeth
• 金额: $ 12.57万
• 依托单位: National Oceanography Centre
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FD012023%2F1
• 关键词: fate; freshwater; tidally; stirred; shelf

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.

大陆架海域为河口和海洋之间提供了一个重要的界面，淡水、悬浮颗粒物以及由此产生的碳、营养物质和人为污染物通过该界面进行交换。虽然大陆架海域的洋流受潮汐支配，但通常是弱得多的残余环流决定了淡水的长期命运。因此，预测水（及其负荷）在这些关键界面上的交换的一个至关重要的先决条件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，分层水平和垂直混合率（称为潮汐张力）中的“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模型无法重现这些地区盐度（即淡水）的正确分布，是因为它们无法正确模拟潮汐张力机制。我们的建议是研究潮汐张力在确定陆架海淡水的离岸通量方面的重要性。“潮汐搅拌陆架海的近海淡水通量主要由潮汐张力决定”这一假设将通过确定和量化决定潮汐搅拌陆架海淡水命运的关键过程来检验。为了达到这个目标，我们将使用海岸天文台的观测和最先进的数值模式预测。