| The Pacific Ocean and its relationship to the climate of the Pacific/North America region, as well as the Northern Hemisphere (NH) and the entire globe has been investigated for many decades. Despite the considerable attention that ocean-atmosphere interactions have received, many fundamental questions still remain. Does the El Niño-Southern Oscillation (ENSO) force responses in the midlatitude atmosphere that are distinct from the atmosphere's internal variability? What is the role of tropical Pacific non-ENSO sea-surface temperature (SST) variability? To what degree does the tropical Pacific affect the extratropical atmosphere, or is the North Pacific primarily responsible for changes in the midlatitude atmospheric circulation? Can SST variability in the tropics alone, or in the North Pacific, account for atmospheric circulation variability, or is it the basin-wide SST variability? It is the goal of this dissertation to use multivariate statistical approaches to determine the major patterns of Pacific Ocean-NH atmospheric variability, whether the NH circulation is linked more closely with the tropical, or the North Pacific, and the degree to which ENSO factors into these ocean-atmosphere interactions.; The strongest association between the Pacific Ocean and the NH circumpolar vortex is a multi-decadal SST pattern similar to the Pacific Decadal Oscillation that is unaffected by ENSO, yet is linked more closely to the tropical Pacific. In fact, this multi-decadal pattern likely represents the true and unique multi-decadal signal in the climate of the Pacific-NH system. The pattern's SST variability is linked with upstream circulation variability over Eurasia. The second-strongest spatial and temporal patterns of ocean-atmosphere interaction depict ENSO-like interannual variability, and the analogous atmospheric circulation is characterized by PNA-like variability over the central-eastern Pacific. As this second ocean-atmosphere pattern essentially depicts ENSO-like variability, it is obviously affected by ENSO. However, the associated vortex patterns are not, suggesting that the PNA-like circulation is not linked with ENSO. In fact, this atmospheric pattern does not seem to be linked to the tropical Pacific at all, but instead to the North Pacific. The subsequent patterns of ocean-atmosphere interaction depict local air-sea feedbacks that are not reconcilable with known patterns of ocean or atmosphere variability. However, these local interactions between the Pacific and the NH are also more closely associated with the North Pacific than the tropics and ENSO is not a dominant player. The implications of these findings are that on interannual timescales the tropical Pacific is perhaps less important in affecting NH climate than previously thought, while on multi-decadal timescales there is a stronger link between the midlatitude atmosphere and non-ENSO tropical variability. |
