Higher frequency of Central Pacific El Niño events in recent decades relative to past centuries

Abstract

El Nino events differ substantially in their spatial pattern and intensity. Canonical Eastern Pacific El Nino events have sea surface temperature anomalies that are strongest in the far eastern equatorial Pacific, whereas peak ocean warming occurs further west during Central Pacific El Nino events. The event types differ in their impacts on the location and intensity of temperature and precipitation anomalies globally. Evidence is emerging that Central Pacific El Nino events have become more common, a trend that is projected by some studies to continue with ongoing climate change. Here we identify spatial and temporal patterns in observed sea surface temperatures that distinguish the evolution of Eastern and Central Pacific El Nino events in the tropical Pacific. We show that these patterns are recorded by a network of 27 seasonally resolved coral records, which we then use to reconstruct Central and Eastern Pacific El Nino activity for the past four centuries. We find a simultaneous increase in Central Pacific events and a decrease in Eastern Pacific events since the late twentieth century that leads to a ratio of Central to Eastern Pacific events that is unusual in a multicentury context. Compared to the past four centuries, the most recent 30 year period includes fewer, but more intense, Eastern Pacific El Nino events. Compared to the past few centuries, Central Pacific El Nino events have become more frequent, whereas the number of Eastern Pacific events has declined in the most recent decades, according to reconstructions from a network of seasonally resolved coral records.