Coastal Sulfur Plumes off Peru During El Niño, La Niña, and Neutral Phases

Abstract

For the first time, the impact of the El Niño-Southern Oscillation (ENSO) on the surface sulfur plumes off the Peruvian upwelling system has been studied. The investigations demonstrated a strong correlation between the ENSO and the sulfur plumes in the coastal areas of Callao and Pisco. During the El Niño phases, the sulfur plumes disappeared almost completely because of equatorial remotely forced oxygenation episodes. The La Niña events were associated with strong oxygen deficiency over the Peruvian shelf, supporting the formation of hydrogen sulfide and, consequently, the occurrence of sulfur plumes. This impact was smaller at Callao, because the La Niña phases in this coastal area were interrupted by weak oxygenation events. During the neutral phases, oxygen-poor waters were also present in the Peruvian shelf areas, promoting the large size of sulfur plumes. However, they were not forced by the remotely driven processes resulting from ENSO phenomena.