Liu F. Y., Zhang W. J., Jin F. F., Jiang F., Boucharel Julien, Hua S. Q. (2023). New insights into multiyear La Nina dynamics from the perspective of a near-annual ocean process. Journal of Climate, 36 (21), 7435-7450. ISSN 0894-8755.
Titre du document
New insights into multiyear La Nina dynamics from the perspective of a near-annual ocean process
Liu F. Y., Zhang W. J., Jin F. F., Jiang F., Boucharel Julien, Hua S. Q.
Source
Journal of Climate, 2023,
36 (21), 7435-7450 ISSN 0894-8755
El Nino-Southern Oscillation (ENSO) exhibits highly asymmetric temporal evolutions between its warm and cold phases. While El Nino events usually terminate rapidly after their mature phase and show an already established transition into the cold phase by the following summer, many La Nina events tend to persist throughout the second year and even reintensify in the ensuing winter. While many mechanisms were proposed, no consensus has been reached yet and the essential physical processes responsible for the multiyear behavior of La Nina remain to be illustrated. Here, we show that a unique ocean physical process operates during multiyear La Nina events. It is characterized by rapid double re-versals of zonal ocean current anomalies in the equatorial Pacific and exhibits a fairly regular near-annual periodicity. Mixed-layer heat budget analyses reveal comparable contributions of the thermocline and zonal advective feedbacks to the SST anomaly growth in the first year of multiyear La Nina events; however, the zonal advective feedback plays a dominant role in the reintensification of La Nina events. Furthermore, the unique ocean process is identified to be closely associated with the preconditioning heat content state in the central to eastern equatorial Pacific before the first year of La Nina, which has been shown in previous studies to play an active role in setting the stage for the future reintensification of La Nina. Despite systematic underestimation, the above oceanic process can be broadly reproduced by state-of-the-art cli-mate models, providing a potential additional source of predictability for the multiyear La Nina events.
Plan de classement
Sciences du milieu [021]
;
Limnologie physique / Océanographie physique [032]
