The Maintenance of Deep Circulation and Stratification in the Ocean

该项目将探索维持海洋深层分层和环流的机制。一个核心方面将是进一步发展和检验中层和深海环流和分层理论。对于中层和深海的分层现象，目前还没有一套公认的理论。 传统上，人们认为，深层层化是由具有不同温度和盐度特性的多个水团的存在和/或由底流混合维持的，底流混合与纬向翻转环流相结合，可以维持一个分层的深渊。然而，最近的数值研究表明，在一个再入南极绕极通道的存在下，即使在消失的diapycnal扩散的限制，也可以保持深分层。如果这是真的，这将是一个重要的结果，无论是在基本水平上，因为它将对海洋混合和需要大的值的diapycnal扩散，在过去的气候制度的海洋行为，并为碳循环的影响。 研究人员已经为温跃层以下的海洋分层建立了一个概念模型，该模型将进一步发展和扩展为一个定量和可测试的机械理论。 该理论将与数值模拟进行测试，并用于更好地了解是否适用于真实的海洋的结果是什么，在过去的气候海洋环流的后果是什么。智力MeritUnderstanding海洋分层是一个具有挑战性的基本问题，在海洋学。我们建议进一步发展一种新的理论，进行数值模拟，并与替代假设进行比较，以确定深层分层和相关的翻转环流的原因。更广泛的影响海洋的深层环流输送热量，因此对气候系统具有直接的重要性。了解海洋分层和环流是改进预测这种输送的数值模式的一个必要方面。深层环流也可能与二氧化碳的吸收和释放有关，是决定大气中二氧化碳水平的一个重要因素。因此，了解深层环流将有助于我们了解很长时间尺度上气候变化的性质。该提案将支持一位年轻的科学家在一个有前途的职业生涯的门槛。最后，首席研究员将修订一本教科书（Vallis 2006），这本教科书已被一些大学用于大气和海洋动力学的教学，他正在开始撰写第二本关于海洋对气候影响的本科水平的书。

The project will explore the mechanisms of maintenance of the deep stratification and circulation of theocean. A central aspect will be to further develop and to test a theory for the mid-depth and abyssal circulation and stratification. There is no body of accepted theory for the stratification of the mid-depth and abyssal ocean. Traditionally, it has been supposed that the deep stratification is maintained by the presence of multiple water masses with different temperature and salinity properties and/or by diapycnal mixing which, in association with a meridional overturning circulation, can maintain a stratified abyss. However, recent numerical investigations have suggested that, in the presence of a re-entrant Antarctic Circumpolar Channel, deep stratification can be maintained even in the limit of vanishing diapycnal diffusivity. If true, this would be an important result both at a fundamental level and because of the implications it would have for ocean mixing and the need for large values of diapycnal diffusivity, for the behavior of the ocean in past climate regimes, and for the carbon cycle. The investigators have developed a conceptual model for the stratification of the ocean below the thermocline, which will be further developed and extended into a quantitative and testable mechanistic theory. The theory will be tested with numerical simulations, and used to better understand whether the results apply to the real ocean and what the consequences are for ocean circulation in past climates.Intellectual MeritUnderstanding the stratification of the ocean is a challenging fundamental problem in oceanography. We are proposing to further develop a novel theory and to perform numerical simulations, and to compare with alternative hypotheses, to determine the cause of the deep stratification and associated overturning circulation.Broader ImpactsThe deep circulation of the ocean transports heat meridionally and so is of direct importance to the climate system. Understanding the ocean stratification and circulation is a necessary aspect of improving numerical models that predict that transport. The deep circulation is also likely tied to the uptake and release of carbon dioxide, and is an important factor determining the levels of carbon dioxide in the atmosphere. Understanding the deep circulation will therefore help us to understand the nature of climate variability on very long timescales. The proposal will support a junior scientist at the threshold of a promising career. Finally, the lead investigator will be revising a textbook (Vallis 2006) that has been adopted by a number of universities for the teaching of atmospheric and oceanic dynamics, and he is beginning to write a second, undergraduate level, book on the ocean's impact on climate.