Delcroix Thierry, Michel S. L. L., Swingedouw D., Malaize B., Daniau A. L., Abarca-del-Rio R., Caley T., Sémah Anne-Marie. (2022). Clarifying the role of ENSO on Easter Island precipitation changes : potential environmental implications for the last millennium. Paleoceanography and Paleoclimatology, 37 (12), e2022PA004514 [19 p.]. ISSN 2572-4517.
Titre du document
Clarifying the role of ENSO on Easter Island precipitation changes : potential environmental implications for the last millennium
El Nino Southern Oscillation (ENSO) events yield precipitation deficits and ensuing droughts, often damaging regional forests, in many parts of the world. The relative roles of ENSO, other natural climate changes, and anthropogenic factors on the forest clearing of Easter Island over the last millennium are still debated. Here, we analyze Easter Island precipitation changes using in situ, satellite-derived and reanalysis products spanning the last 4-7 decades, and 46 monthly 156-year-long (1850-2014) simulations derived from 25 CMIP5 and 21 CMIP6 (Coupled Model Intercomparison Project phases 5 and 6) General Circulation Models. Our analysis shows that La Nina events, the cold phases of ENSO, cause precipitation deficits of -0.2 to -0.3 standard deviation (relative to long-term mean) in all analyzed data types. ENSO-like events are further examined over the last millennium (850-1981). A new multiproxy reconstruction of the NINO3.4 index based on proxy records from the Past Global Changes 2k database and Random Forest method is produced. Our reconstruction reveals unusual high recurrences of La Nina-like situations during the fifteenth to seventeenth centuries, which likely induced significant precipitation deficits on the island. These situations are compared to published vegetation reconstructions based on pollen analyses derived from sedimentary cores collected in three island sites. We conclude the environmental consequences of cumulative precipitation deficits over long-lasting La Nina-like situations reconstructed here over the fifteenth to seventeenth centuries were likely favoring drought and forest flammability. La Nina events should be better accounted for among the causes of forest clearing on Easter Island.
Plan de classement
Sciences du milieu [021]
;
Limnologie physique / Océanographie physique [032]
;
Géologie et formations superficielles [064]
