Holocene hydroclimatic variability in the tropical Pacific explained by changing ENSO diversity

Area of Science:

• Paleoclimatology
• Climate Dynamics
• Ocean-Atmosphere Interactions

Background:

• Paleoclimate evidence for El Niño-Southern Oscillation (ENSO) during the Holocene is conflicting, hindering understanding of its response to past climate forcings.
• Eastern Pacific records suggest intensifying ENSO variability, while central Pacific records show high variability unrelated to insolation forcing.

Purpose of the Study:

• To reconcile conflicting paleoclimate records of ENSO during the Holocene.
• To investigate the influence of ENSO spatial pattern diversity and hydroclimatic impact strength on observed variability.

Main Methods:

• Utilized climate model simulations to analyze ENSO behavior.
• Examined changes in the relative frequency of three preferred El Niño spatial patterns (Eastern Pacific, Central Pacific, Coastal).
• Assessed the varying hydroclimatic impacts associated with different ENSO event types.

Main Results:

• Conflicting Holocene ENSO records can be reconciled by accounting for shifts in the frequency of ENSO's spatial patterns.
• The strength of hydroclimatic impacts varies significantly across different ENSO event types.

Conclusions:

• The relationship between ENSO diversity and variance is key to interpreting paleo-ENSO records and understanding ENSO's response to external forcings.
• This framework can be applied to climate model simulations to evaluate the realism of ENSO projections in a changing climate.