Investigating the Influence of Atmospheric Changes on the Variability of the North Pacific Using a Fully Coupled GCM

In this study we attempt to investigate whether changes in atmospheric concentrations in ozone and greenhouse gases (GHGs), including CO₂, N₂O, and methane, have an influence on decadal-scaled oceanic and atmospheric dynamics in the Northeast Pacific. Using a coupled ocean-atmosphere GCM (FOAM1.5) we simulate climatic conditions for the pre-industry and the present day while focusing on the North Pacific. We explore how the ozone hole over the Southern Hemisphere and increased concentrations in GHGs observed in the present day influence the Pacific (Inter)Decadal Oscillation (PDO) and the North Pacific High (NPH), two dominant modes of variability in the North Pacific. In each model we examine the spatial and temporal patterns of the NPH, sea-surface temperatures and salinities (SSTs, SSSs) as well as wind and ocean currents on the order of interannual to interdecadal time scales. We find that within these simulations the influence of the prescribed atmospheric perturbations is small. We observe that the present-day SST and SSS fields of the Northeast Pacific are similar in both model runs as well as sea level pressure. In both simulations the PDO dominates the patterns of variability in the North Pacific and does not appear to change either in character or expression as a result of the atmospheric perturbations. The atmospheric change caused by the rise in GHG concentrations and the decline in ozone is not prominent as a primary influence on the decadal scale variability within the Northeast Pacific.