The ocean response to atmospheric intraseasonal variability in the tropical Pacific Ocean
The ocean response to atmospheric intraseasonal variability in the tropical Pacific Ocean is investigated using the URI Ocean General Circulation Model. The model performance in simulating the oceanic annual cycle is evaluated by examining its sensitivities to details of the air-sea flux parametrization, different sources for the wind forcing products, and the meridional extent of the model domain. The model fields provide adequate initial conditions for the model experiments with anomalous intraseasonal atmospheric forcing. ^ We start with a simple experiment in which a resting ocean is forced with a brief wind burst and proceed with experiments for a circulating ocean forced with intraseasonal wind oscillations superimposed upon climatological air-sea fluxes. The main effect of the realistic background ocean conditions is that the strongest response to anomalous wind forcing is observed along the equator in the vicinity of the eastern edge of the western Pacific warm pool. It is argued that this zonally non-uniform ocean response is primarily due to significant vertical and longitudinal variations of the salinity field associated with the western Pacific freshwater pool. Eastward advection, by remotely forced Kelvin waves and baroclinic modes formed via nonlinear interaction between these waves and zonally-varying background ocean stratification, is identified as an important mechanism of the Eastern Warm Pool Covergence Zone (EWPCZ) displacement. ^ The magnitude of the simulated rectification of the intraseasonal Madden-Julian Oscillation atmospheric perturbations into the annual cycles of sea surface temperatures, salinities, and zonal currents in the western Pacific is found to be comparable to the annual variability itself. This result indicates that the ocean's response strongly depends on seasonally varying background ocean conditions, such as the position and strength of the salinity front associated with the EWPCZ. The important role of salinity is further illustrated in experiments with combined wind and freshwater MJO anomalies. ^
Alexander Gennadievich Kochurov,
"The ocean response to atmospheric intraseasonal variability in the tropical Pacific Ocean"
Dissertations and Master's Theses (Campus Access).