Coastal Sulfur Plumes off Peru During El Nino, La Nina, and Neutral Phases

For the first time, the impact of the El Nino-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 Nino phases, the sulfur plumes disappeared almost completely because of equatorial remotely forced oxygenation episodes. The La Nina 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 Nina 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. Plain Language Summary In the Peruvian coastal area, hydrogen sulfide outbreaks and their resulting coastal sulfur plumes influence the marine ecosystem and the fishing industry by their toxic properties. The relation between the sulfur plumes and the well-known El Nino and La Nina events was investigated. The sulfur plumes were detected in remotely sensed satellite data through their characteristic milky turquoise discoloration. The results demonstrated a strong correlation of the El Nino and La Nina events with the coastal sulfur plumes as well as their dependence on the oxygen supply in the Peruvian shelf area.