Recent multidecadal strengthening of the Walker circulation across the tropical Pacific

Abstract

The Walker circulation is a large overturning cell that spans the tropical Pacific Ocean. Fluctuations in this circulation reflect changes in tropical heating, and have global impacts on temperature and precipitation. Analysis of trends in sea-level pressure from ten data sets reveals strengthening of the Walker circulation in line with increasing global temperature, which is counter to current model predictions. The Pacific Walker circulation is a large overturning cell that spans the tropical Pacific Ocean, characterized by rising motion (lower sea-level pressure) over Indonesia and sinking motion (higher sea level-pressure) over the eastern Pacific1,2. Fluctuations in the Walker circulation reflect changes in the location and strength of tropical heating, so related circulation anomalies have global impacts3,4. On interannual timescales, the El Niño/Southern Oscillation accounts for much of the variability in the Walker circulation, but there is considerable interest in longer-term trends and their drivers, including anthropogenic climate change5,6,7,8,9,10,11,12. Here, we examine sea-level pressure trends in ten different data sets drawn from reanalysis, reconstructions and in situ measurements for 1900–2011. We show that periods with fewer in situ measurements result in lower signal-to-noise ratios, making assessments of sea-level pressure trends largely unsuitable before about the 1950s. Multidecadal trends evaluated since 1950 reveal statistically significant, negative values over the Indonesian region, with weaker, positive trends over the eastern Pacific. The overall trend towards a stronger, La Niña-like Walker circulation is nearly concurrent with the observed increase in global average temperatures, thereby justifying closer scrutiny of how the Pacific climate system has changed in the historical record.

Cite this article

L’Heureux, M., Lee, S. & Lyon, B. Recent multidecadal strengthening of the Walker circulation across the tropical Pacific. Nature Clim Change 3, 571–576 (2013). https://doi.org/10.1038/nclimate1840

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