Ocean mixing and internal waves

在过去的几十年里，海洋学家建立了类似于天气模型的海洋数值模型。与天气模型一样，随着计算能力的增强，改进也随之而来，这使得模拟更大范围的观察到的海洋现象成为可能。例如，第一批海洋模型太粗糙，无法解决大约10公里大小的海洋涡流，但现在已经有可能做到这一点，至少对于短期预测来说是这样。不幸的是，有一些重要的海洋现象太小了，任何可以想象的计算机都无法处理。海洋混合就是一个很好的例子，它发生在厘米尺度上，远远低于今天模型的10公里限制。海洋测量显示，这种混合以复杂的模式发生，模型的敏感性测试表明，这些模式的微小变化会造成海洋整体状态的巨大变化。这让海洋学家们左右为难。唯一的解决方案似乎是将混合过程参数化，即仅使用模型可以直接处理的大尺度特性来估计其影响。我的工作重点是为各种海洋混合现象创建这样的参数化。未来几年的重点将是沿海水域的高频内波造成的混合。在NSERC和CFCAS的资助下，我的团队收集了一套关于这一现象的特别详细的观察结果。他们希望结合小规模的数值模拟来开发这种混合模式的更可靠的参数。

Over the past several decades, Oceanographers have created numerical models of the ocean, akin to weather models. As with weather models, improvements have come along as computing power has increased, making it possible to simulate a wider fraction of the observed ocean phenomena. For example, the first ocean models were too coarse to resolve the approximately ten-kilometre scale ocean eddies, but it is now becoming possible to do this, at least for short-term predictions. Unfortunately, there are important ocean phenomena that are too small to be handled by any imaginable computer. A case in point is ocean mixing, which occurs on centimetre scales, far below the 10-kilometre limit of today's models. Ocean measurements reveal that this mixing occurs in complicated patterns, and sensitivity tests with models indicate that small variations in those patterns create large changes in the overall state of the ocean. That leaves Oceanographers in a bind. The only solution seems to be to parameterize the mixing, i.e. to approximate its affects using only the large-scale properties that the models can handle directly. My work centres on creating such parameterizations of various ocean mixing phenomena. The focus over the next several years will be mixing caused by high-frequency internal waves in coastal waters. Funded by NSERC and CFCAS, my group has amassed a particularly detailed set of observations of the phenomenon. The hope is to use this along with small-scale numerical simulations to develop more reliable parameterizations of this mode of mixing.