Timing of subsurface heat magnitude for the growth of El Niño events
The subsurface heat buildup in the western tropical Pacific and the recharge phase in equatorial heat content are intrinsic elements of El Niño–Southern Oscillation, leading to changes in zonal wind stress, sea surface temperature, and thermocline tilt that characterize the growing and mature phases of El Niño (EN) events. Here we use numerical simulations to study the impact on subsequent EN episodes of a sudden increase or decrease in ocean heat content during the recharge phase and compare results with previous studies in which this perturbation is prescribed earlier during the tilting mode. We found that while not substantially affected by the phase at which a sudden rise in heat content is prescribed, the timing and magnitude of the events are very sensitive to the phase at which a major decrease is imposed. The different response to the phase of increases and decreases substantiates the importance of nonlinear subsurface ocean dynamics to the onset and growth of EN episodes and provides insight into the irreversibility of the events at different stages of the oscillation.
Additional Information© 2017 American Geophysical Union. Received 14 JUN 2017; Accepted 30 JUL 2017; Accepted article online 3 AUG 2017; Published online 19 AUG 2017. J.B. gratefully acknowledges funding from the European Commission through a Marie Curie International Outgoing Fellowship (project MEMENTO from the FP7-PEOPLE-2011-IOF call) and a Marie Curie Individual Fellowship (project ACCLIM from the H2020-MSCA-IF-2016 call) and from the European Commission and the Catalan Government through a Marie Curie-Beatriu de Pinós Fellowship (project 00068 from the BP-DGR-2014-B call). All data sets used in this study are presented in this paper and in the supporting information file.
Supplemental Material - grl56266-sup-0001-2017GL074557-SI.pdf