A record-high ocean bottom pressure in the South Pacific observed by GRACE

In late 2009 to early 2010, the Gravity Recovery and Climate Experiment (GRACE) satellite pair observed a record increase in ocean bottom pressure (OBP) over a large mid‐latitude region of the South East Pacific. Its magnitude substantially larger than other oceanic events in the Southern Hemisphere found in the entire GRACE data records (2003–2010) on multi‐month time scales. The OBP data help to understand the nature of a similar signal in sea surface height (SSH) anomaly observed by altimetry: the SSH increase is mainly due to mass convergence. Analysis of the barotropic vorticity equation using scatterometer data, atmospheric reanalysis product, and GRACE and altimeter observations suggests that the observed OBP/SSH signal was primarily caused by wind stress curl associated with a strong and persistent anticyclone in late 2009 in combination with effects of planetary vorticity gradient, bottom topography, and friction. In addition to the nature and forcing, the impact of the record event on the Antarctic environment and Southern Ocean circulation and the potential connection to climate variability was investigated.