Predictive Understanding of the Oceans' Wind-Driven Circulation on Interdecadal Time Scales

The goal of this project was to obtain a predictive understanding of a major component of the climate system’s interdecadal variability: the oceans’ wind-driven circulation. To do so, we developed and applied advanced computational and statistical methods to the problem of climate variability and climate change. The methodology was developed first for models of intermediate complexity, such as the quasi-geostrophic and the primitive equations, which describe the wind-driven, near-surface flow in mid-latitude ocean basins. Our computational work consisted in developing efficient multi-level methods to simulate this flow and study its dependence on physically relevant parameters. Our oceanographic and climate work consisted in applying these methods to study the bifurcations in the wind-driven circulation and their relevance to the flows observed at present and those that might occur in a warmer climate. Both aspects of the work are crucial for the efficient treatment of large-scale, eddy-resolving numerical simulations of the oceans and an increased understanding and better prediction of climate change. Considerable progress has been achieved in understanding ocean-atmosphere interaction in the mid-latitudes. An important by-product of this research is a novel approach to explaining the North Atlantic Oscillation