Stand-Alone Eastern Pacific Coastal Warming Events

Abstract

A pronounced warm anomaly occurred at the Peruvian coast in early 2017. This “Coastal Niño” caused heavy rainfalls, leading to flooding in Peru and Ecuador. At the same time, neutral conditions prevailed in the equatorial Pacific. Using observational sea surface temperature data sets and an ocean reanalysis product for the time period 1900 to 2010, previous similar events are investigated. Eighteen coastal warming events without corresponding equatorial Pacific warming are identified. Further analysis shows, however, that only four of these events are not connected to the central equatorial Pacific. All other periods of strong coastal warm anomalies are directly followed or preceded by El Niño-like conditions. The “stand-alone” coastal warming events are characterized by comparatively low equatorial heat content. We thus hypothesize that the depleted heat content in the equatorial Pacific in the wake of the strong 2015/2016 El Niño prevented the warming to spread westward in 2017.