A Modeling Study of the Intrinsic Variability of the Gulf-Stream and Kuroshio Extension Systems

0221516 PrimeauThe本项目的目的是测试的假设，观察到的变异性是一种表现的内在变异性与多重平衡之间的过渡。要做到这一点，调查人员将适用于最近开发的数值分岔分析的方法，越来越现实的层次结构的海洋模型计算的解决方案分支中发现的更简单的模型。将测试以下明确的标准。如果不符合，则必须拒绝该假设。1.与细长的再循环环流的平衡应该是相对较不稳定的平衡与细长的环流是一致的观察，涡动活动减少期间的细长的环流2。与细长的再循环环流相关的不稳定模式应具有在射流下游区域占主导地位的振幅模式，而收缩的再循环环流的不稳定模式应具有在上游区域占主导地位的振幅模式，这与涡流变化在细长状态下向下游移动的观察结果一致。急流延伸的平均纬向路径应该更北的平衡与拉长的再循环涡旋是一致的观察，墨西哥湾流和黑潮延伸区的纬向平均路径向北移动在拉长状态。学生将接受海洋建模和将动力系统理论应用于气候问题的培训。此外，还将制作一个对海洋模型进行数值分叉分析的软件包，并提供给社区。观察到的低频变异性的大规模模式是内在变异性的结果的可能性是一个令人兴奋的，因为观察表明，这些目前的变化是显着的？这可能是维持海表温度异常的主要因素，因此可能有助于中纬度气候变率。

0221516 PrimeauThe purpose of this project is to test the hypothesis that the observed variability is a manifestation of intrinsic variability associated with the transitions between multiple equilibria. To do this the investigators will apply the recently developed methods of numerical bifurcation analysis to a hierarchy of ocean models with increasing realism to compute the solution branches found in the simpler model. The following clear criteria will be tested. If they are not met, the hypothesis must be rejected. 1. The equilibria with elongated recirculation gyres should be relatively less unstable than the equilibria with elongated gyres to be consistent with the observation that eddy activity decreases during periods of elongated gyres 2. The unstable modes associated with elongated recirculation gyres should have amplitude patterns that dominate in the downstream region of the jet, and those for the contracted recirculation gyres should have amplitude patterns that dominate in the upstream region, to be consistent with the observation that the eddy variability moves downstream during elongated states.3. The mean zonal path of the jet extension should be further north for equilibria with elongated recirculation gyres to be consistent with the observation that the zonal mean path of the Gulf Stream and Kuroshio Extension moves northward during elongated states.Through this study a Ph.D. student will be trained in ocean modeling and in the application of dynamical systems theory to climate problems. In addition a software package to do numerical bifurcation analysis of ocean models will be produced and made available to the community. The possibility that the observed large-scale patterns of low-frequency variability are the result of intrinsic variability is an exciting one because observations show that these current changes are signi?cant contributors to the maintenance sea surface temperature anomalies and thus could contribute to mid-latitude climate variability.