Mechanisms governing sea surface temperature anomalies in the eastern tropical Pacific Ocean associated with the boreal winter Madden-Julian Oscillation

The study objective is to explore the relationship between the Madden-Julian Oscillation (MJO) and intraseasonal sea surface temperature (SST) variability in the eastern tropical Pacific Ocean. Previous studies have illustrated the connection between MJO and the production of zonally large (> 2000 km), persistent (similar to weeks) SST anomalies. Those studies suggested that vertical processes, such as advection and entrainment, forced remotely by winds in the western Pacific (via Kelvin waves) may be the mechanism controlling SST changes. To overcome limitations in situ observations (e. g., sparse and missing data/quantities) and to develop a more comprehensive physical understanding, this study examines the relationship using an ocean general circulation model. A simulation was conducted in which the model was forced by idealized MJO conditions constructed from observed forcing fields. Analysis of the model simulation shows an equatorial Kelvin wave initiated in the western Pacific Ocean. However, analysis of the model's mixed layer temperature heat budget shows that in the eastern Pacific meridional advection plays the major role in the sea surface temperature change, 61.8% of the warming phase and 70.7% of the cooling phase percent heat budget. Zonal advection is the second most important term to the warming phase (20.5%) with the vertical advection and mixing term being second for the cooling phase (37.6%). In addition, the results indicate that the primary component of the meridional advection is the advection of the mean meridional temperature gradient by MJO-forced meridional current anomalies. The implications and caveats of these results are discussed in relationship to results in prior studies.