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Abstract. The El Niño-Southern Oscillation (ENSO) is recognized as the dominant driver of global vegetation variability on interannual timescales. Here, we examine how ENSO affects decadal to multi-decadal vegetation variability. We address this with partial spectral and mediation analysis applied to multi-centennial pre-industrial control simulations from 11 CMIP6 models with dynamic leaf area index (LAI). We find a spectral reddening of ENSO-driven vegetation variability, with a 20 %–25 % amplification of the LAI signal at multi-decadal timescales and a 25 %–65 % reduction at interannual timescales. This amplification is primarily concentrated in tropical hotspots, such as the northern Amazon and Southeast Asia, which dominate the global gain signal. The coherence between ENSO and LAI at these multi-decadal timescales is largely governed by a direct pathway (88 %), while the Pacific Decadal Oscillation (PDO) only acts as a weak mediator (12 %). In contrast, the Atlantic Multidecadal variability (AMV) exhibits significant multi-decadal coherence with vegetation but lacks the associated spectral reddening. Mechanistically, ENSO-driven LAI persistence originates from ENSO-induced changes in near-surface soil moisture, which is subsequently amplified by vegetation dynamics. This ENSO-related memory also manifests in Gross Primary Production (GPP), but it is suppressed in Net Primary Production (NPP) by a compensatory increase in autotrophic respiration. Our results illustrate how terrestrial persistence acts as a predictable, non-oceanic source of decadal variability, which could help extend the skill of climate predictions and improve hydrological risk management.
Fahrenbach et al. (Mon,) studied this question.