Premium
Changes in ENSO Activity During the Last 6,000 Years Modulated by Background Climate State
Author(s) -
An SoonIl,
Im SeulHee,
Jun SangYoon
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl076250
Subject(s) - orbital forcing , climatology , forcing (mathematics) , advection , proxy (statistics) , el niño southern oscillation , environmental science , sea surface temperature , multivariate enso index , climate model , climate change , atmosphere (unit) , atmospheric sciences , geology , southern oscillation , meteorology , physics , oceanography , insolation , machine learning , computer science , thermodynamics
Various proxy records show that El Niño–Southern Oscillation (ENSO) activity has changed from calm to active during the last 6,000 years. However, it is so far unclear whether orbital forcing has solely induced such a dramatic change. In this study, we performed a transient run for the last 6,000 years using an Earth system model of intermediate complexity affected by orbital forcing only without changes due to other climate forcing, and then its time‐varying background states were implemented into an intermediate atmosphere‐ocean coupled model for ENSO. ENSO activity simulated by the intermediate atmosphere‐ocean coupled model during the last 6,000 years resembled the observed proxy data, inferring that orbital forcing mainly leads to changes in ENSO activity during the last 6,000 years. From additional sensitivity experiments, we found that a change in sea surface temperature background conditions is primarily responsible for the observed ENSO activity over the last 6,000 years through modifying the anomalous horizontal thermal advection of the mean SST gradient.