Collaborative Research: Mid-Latitude Modes of Climate Variability

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0221066/0220700 Ghil/DewarIt is proposed to study coupled mid-latitude climate variability on decadal and longer time scales. The main hypothesis is that a critical component of this variability arises from intrinsic ocean sources. This hypothesis will be analyzed using a numerical model of the coupled ocean-atmosphere system, focusing on the oceans' wind-driven variability, rather than on that of the thermohaline circulation. An intermediate complexity model is ideally suited to test this hypothesis. The model consists of an oceanic and an atmospheric component, each of which captures the turbulent nature of the corresponding fluid. The new feature of our proposal is in coupling these two models, and analyzing the nature of the coupled turbulence that results. To achieve turbulence simultaneously in the two fluids requires working with reduced models of each. One fundamental problem faced by more dynamically complete models in achieving this same goal is insufficient computer power. Parameterization of small-scale oceanic variability as a feedback on the ocean's general circulation and on climate thus stands as a critical problem for understanding and predicting coupled climate variability. Initial steps will be taken towards formulating such parameterizations and testing them within this model. Coupled general circulation models also face the problem that the phenomenology of coupled behavior is not currently known, thus complicating the analysis and interpretation of model results. This work will contribute to a solution of this problem by providing a conceptual paradigm for coupled system behavior. The intellectual merit of this proposal is to analyze a viable hypothesis relevant to the coupled climate problem on inter-decadal timescales. The broader impacts of the work lie in developing scientific partnerships between two leading institutions (UCLA and FSU) in this field, broadly disseminating the results of our work by means of publications, seminars and presentations at national and international meetings, and addressing a problem of crucial societal importance in climate prediction.