The warm Blob in the northeast Pacific—the bridge leading to the 2015/16 El Niño

Abstract

We address the occurrence of the warm anomaly, known as the Blob, that developed from late 2013 to 2015 in the northeast Pacific and its connection with the El Niño-Southern Oscillation (ENSO) variability. The warm Blob results from the enhanced second ocean-atmosphere (O-A) coupled mode of variability in the tropical and North Pacific, representing a small part of the Victoria mode (VM) in the northeast Pacific forced by the strengthened North Pacific Oscillation-like atmospheric pattern since 2013. We also show that this second O-A mode reflects the meridional variability through the tropical-extratropical teleconnection and is an important precursor to the ENSO variability. The process is confirmed by the coupled patterns that evolved from late 2013 to 2016 and the multi-year persistence of the warm Blob. We emphasize the role of evolving basin-scale VM but not the warm Blob itself prior to the ENSO variability. Hence, the Blob and the most recent 2015/16 El Niño, which differs significantly from the other large El Niños in terms of the triggering hemisphere, are actually linked rather than independent phenomena.

Relative Contributions of North and South Pacific Sea Surface Temperature Anomalies to ENSO

“…Previous studies suggest that the initiation and onset of ENSO events in the tropical Pacific can be partly associated with variations in the SST fields in the extratropical North Pacific (represented by the VM mode) as well as variations in the extratropical South Pacific (represented by the SPQ mode; Ding, Li, Tseng, Sun, et al, ; Ding, Li, & Tseng, ; Tseng, Ding, et al, ). Here using observational data, we demonstrate that both VM and SPQ SST forcing during boreal spring can serve as a trigger for ENSO events.…”

The Defining Characteristics of ENSO Extremes and the Strong 2015/2016 El Niño

“…The VM, which is closely related to the North Pacific Gyre Oscillation (Di Lorenzo et al, ), has been suggested to trigger ENSO events through alterations of air‐sea coupling in the tropical Pacific and subsurface ocean heat anomalies leading to surface warming in the central Pacific (Ding, Li, Tseng, et al, ). Tseng et al () suggested that the Blob is part of VM evolution leading to the emergence of the 2015/2016 El Niño. Figure d shows that the VM positive phase during 2015 was particularly strong, following another strong positive state in 2014, before turning weakly negative in 2016.…”

Global Search for Autumn‐Lead Sea Surface Salinity Predictors of Winter Precipitation in Southwestern United States

“…When SWUS experiences anomalously wet winters, a strong dipole of cool water in the western Pacific Ocean and a warm tongue extending from the central to eastern equatorial Pacific is present in the preceding autumn. The warm tongue is coupled with the Pacific Warm Blob, which is characteristic of warm waters along the western coast of North America and linked to the strong 2015–2016 El Niño event (Tseng et al, ). The SSS signal is likely linked to ENSO.…”

“…Geophysical Research Letters preceding autumn. The warm tongue is coupled with the Pacific Warm Blob, which is characteristic of warm waters along the western coast of North America and linked to the strong 2015-2016 El Niño event (Tseng et al, 2017). The SSS signal is likely linked to ENSO.…”