Amaya, D., S.-P. Xie, A. J. Miller and M. J. McPhaden, 2015:
Seasonality of tropical Pacific decadal trends associated with the 21st
century global warming hiatus
Journal of Geophysical Research-Oceans,
120, 6782-6798.
Abstract.
Equatorial Pacific changes during the transition from a non-hiatus period (pre-1999) to
the present global warming hiatus period (post-1999) are identified using a combination
of reanalysis and observed data sets. Results show increased surface wind forcing has
excited significant changes in wind-driven circulation. Over the last two decades, the core
of the Equatorial Undercurrent intensified at a rate of 6.9 cm s-1 decade-1. Similarly,
equatorial upwelling associated with the shallow meridional overturning circulation
increased at a rate of 2.0 x 10-4 cm s-1 decade-1 in the central Pacific. Further, a seasonal
dependence is identified in the sea surface temperature trends and in subsurface
dynamics. Seasonal variations are evident in reversals of equatorial surface flow trends,
changes in subsurface circulation, and seasonal deepening/shoaling of the thermocline.
Anomalous westward surface flow drives cold-water zonal advection from November to
February, leading to surface cooling from December through May. Conversely, eastward
surface current anomalies in June-July drive warm-water zonal advection producing
surface warming from July to November. An improved dynamical understanding of how
the tropical Pacific Ocean responds during transitions into hiatus events, including its
seasonal structure, may help to improve future predictability of decadal climate
variations.
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