Reconciling eastern and central Pacific paleo-ENSO proxies: the role of coastal El Niño events.

Coastal El Niño events have significant hydroclimate impacts along the Eastern equatorial Pacific coast, including extreme precipitation that leads to severe flooding along the Ecuadorian and northern Peruvian coasts and the Andean elevations. During coastal El Niño events, the anomalous sea surface temperatures are confined to the NINO1+2 region, thus limiting the global teleconnections commonly associated with the basin-scale ENSO events. Hence, these events have been largely neglected in the interpretation of paleo-ENSO proxies. In this talk, I will first show that coastal El Niño events dominate extreme rainfall in the Ecuadorian Andes compared to basin-scale Eastern or Central Pacific El Niños, therefore they should be considered when assessing paleoclimate proxy signals from the region. I will then present the response of coastal El Niño events to paleoclimate forcing during the past 24,000 years, as modeled by a state-of-the-art earth system model (NCAR's CESM). I will show that the externally-forced signal is mostly precessional, associated with local seasonal changes in the NINO1+2 region and extratropical influences, and is consistent with lake sediment records from the area. Thus, if the primary contribution to the signal in paleoclimate proxy records from the far eastern Pacific regions is from coastal events, then one may not expect an agreement between these proxies and proxies from other areas in the Pacific which record basin-scale ENSO events. Based on these insights, I will quantify the influence of the simulated relative changes in Eastern, Central Pacific and coastal El Niño in the past 24,000 years in proxy-critical regions and will illustrate the usefulness of this approach in reconciling seemingly conflicting paleo-ENSO evidence from across the Pacific.