Collaborative Research: Understanding Tidal Resonances in the Present-Day and Ice-Age Oceans

合作研究：了解当今和冰河时​​代海洋的潮汐共振

• 批准号: 0623611
• 负责人: Samar Khatiwala
• 金额: --
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-10-01 至 2010-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0623611&HistoricalAwards=false
• 关键词: Collaborative; Research; Understanding; Tidal; Resonances

The suggestion that dissipation of tidal energy contributes significantly to mixing of the abyssal oceans, has renewed interest in tides, and their influence on the large scale ocean circulation. The postulated connection between tides, mixing, and the meridional overturning circulation raises interesting questions regarding the role of tides in the past. Two recent studies have demonstrated that the North Atlantic tides of the most recent ice age were substantially larger than they are today. Ice-age tides differ from those of today because tides are resonant phenomena, and are therefore likely to be quite sensitive to changes in sea level and associated changes in basin geometry. The principal objective of this proposal is to address the question of how the astronomical tidal forcing, sea level and basin geometry, and dissipation conspire to produce the observed tidal response. Motivated by recent advances in forward tide modeling, the proposed research seeks to understand tides of both the present-day and of the ice-ages. There are 3 principal elements to the proposed research: (1) Computation of the normal modes of Laplace's tidal equations for the global ocean at a resolution of 1 degree, (2) Simulations with a global forward model of tides to investigate the oceanic response to different forcing frequencies, basin geometries, and sea-levels; and (3) Interpretation of the forward model results in terms of damped-driven oscillator theory, using, as inputs, the eigenfrequencies and associated spatial patterns determined from the normal mode calculation. An improved understanding of tides and how they respond to sea-level change would be an important step toward being able to address a range of issues related to the impact of tides on the large scale circulation. The work will contribute to our understanding of the relative importance of the spatial structure of the forcing, the forcing frequency, and the dissipation, in setting the amplitude of tides in the present day and in the ice ages. The research has broad impact because tides and tidal dissipation affect oceanic circulation (via tidal mixing), sea ice, floating ice shelves, and continental ice sheets. The work has implications for paleoclimate, because of the effects of tidal mixing on oceanic circulation, and also because ice-age tides were very large in the Labrador Sea, site of the Heinrich event iceberg discharges (tides have been proposed as a factor in the iceberg discharges). Finally, this research will provide a framework for predicting the tides of a future with potentially much higher sea levels, with application for coastal cities. The PIs play an active role in teaching, mentoring, and outreach, and this project will provide continued support for those activities, including support for an undergraduate student who will work on this project under the PIs' direction. Results and numerical code will be made freely available to the research community.

关于潮汐能量耗散的建议对深渊海洋的混合产生了重大贡献，对潮汐的兴趣又引起了人们对大规模海洋循环的影响。 潮汐，混合和子午倾斜循环之间的假定联系提出了有关潮汐在过去的作用的有趣问题。 最近的两项研究表明，最近的冰河时代的北大西洋潮汐比今天大得多。 冰河潮汐与今天的潮汐不同，因为潮汐是谐音现象，因此可能对海平面变化以及盆地几何形状的相关变化非常敏感。 该提案的主要目的是解决天文学潮汐强迫，海平面和盆地几何形状以及耗散如何共同产生观察到的潮汐反应的问题。 在最近的前进建模方面的进展中，拟议的研究试图了解当今和冰期恋时代的潮流。 提出的研究有3个主要要素：（1）以1度的分辨率计算Laplace的潮汐方程的正常模式，（2）具有潮汐的全球前向模型的模拟，以研究对不同强迫频率，盆地几何形状和海平面的海洋反应的响应； （3）对正向模型的解释以阻尼驱动的振荡器理论的形式，将其作为输入，从正常模式计算中确定的特征频率和相关的空间模式。 对潮汐及其对海平面变化的反应的改进理解将是能够解决与潮汐对大规模循环有关的一系列问题的重要一步。这项工作将有助于我们理解强迫的空间结构，强迫频率和耗散的相对重要性，并在当今和冰河时​​代设置潮汐的幅度。这项研究具有广泛的影响，因为潮汐和潮汐耗散会影响海洋循环（通过潮汐混合），海冰，浮冰架和大陆冰盖。由于潮汐混合对海洋循环的影响，这项工作对古气候有影响，也是因为在拉布拉多海，冰河潮汐非常大，海因里希事件事件冰山的排放地点（已经提出了潮汐作为冰山排放的一个因素）。 最后，这项研究将提供一个框架，以预测未来的潮汐，并使用沿海城市的应用可能更高的海平面。 PI在教学，指导和推广方面发挥了积极作用，该项目将为这些活动提供持续的支持，包括支持将在PIS方向上从事该项目的本科生的支持。结果和数值代码将免费提供给研究社区。