Tropical Pacific Sea Level Pressure Trends Indicate a Strengthening Walker Circulation

Linear trends of sea level pressure (SLP) over the tropical Pacific are analyzed over the 20th century using ten observational datasets drawn from model-based reanalysis, statistical reconstructions, and in situ measurements. Observed SLP trends prior to ~1950s appear to be adversely impacted by the lack of in situ data, while the SLP trend estimate after 1950 reflects higher signal to noise. In the recent half-century, SLP trends across Indonesia and the western Pacific Ocean have a significant negative tendency. During the same period, a smaller and less significant positive tendency of SLP trends is evident over the eastern Pacific Ocean. Together, these trends imply a strengthening Walker circulation during the latter half of the 20th century, which is roughly concurrent with the increase in global mean temperature. A decomposition of running 30-year SLP trends indicates that the observed trends can largely be described by the linear superposition of ENSO and the global mean temperature.