Subpolar ocean bottom pressure oscillation and its links to the tropical ENSO

Abstract

Recent analysis of ocean bottom pressure (OBP) data from the Gravity Recovery and Climate Experiment (GRACE) satellites reveals strong El Niño/Southern Oscillation (ENSO)‐like oscillating phenomena in the subpolar gyre of the North Pacific. The oscillation is further enhanced by subtracting the OBP values in the subtropical gyre, indicating a mass imbalance between these two northern gyres in these time‐scales. Such OBP oscillating features have not been reported before. Motivated by the satellite observations, a non‐Boussinesq ocean model that conserves mass rather than volume was used to diagnose the long‐term prospect of the oscillating features. Model simulations from the years 1948 to 2006 demonstrate that the subpolar OBP oscillation correlates closely with the tropical ENSO events. Further analysis of the wind stress curl (WSC) from National Center for Environmental Protection/National Center for Atmospheric Research (NCEP/NCAR) products and sea surface height (SSH) data from altimeters suggests that the tropical ENSO can affect the OBP anomaly of the subpolar gyre through an atmospheric bridge by altering and deepening the Aleutian Low and/or through oceanic waves by enhancing the water mass anomaly in the semi‐closed northern Pacific basin.