Rhee et al. (2025) Topographic Setting Drives the Imprint of the Madden–Julian Oscillation ( MJO ) on Tree Growth in the Northern Sierra Nevada

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: International Journal of Climatology
• Year: 2025
• Date: 2025-11-02
• Authors: George Rhee, Diana L. Thatcher, Katarina J. Warnick, Josh Carrell, Andrew Ford, Jessie George, Victoria Harris, Patrick Lemis, Alan M. Radford, Richard Maxwell, Grant L. Harley
• DOI: 10.1002/joc.70162

## Research Groups -

Short Summary

This study investigates whether conifer tree growth in the northern Sierra Nevada, United States, can serve as a proxy for Madden–Julian Oscillation (MJO) variability. It provides the first documented evidence that Pinus jeffreyi tree-ring chronologies exhibit significant correlations with MJO indices, offering a novel tool for reconstructing past MJO dynamics.

Objective

• To investigate whether tree growth from conifer forests in the northern Sierra Nevada, United States, can serve as a proxy for Madden–Julian Oscillation (MJO) variability.

Study Configuration

• Spatial Scale: Northern Sierra Nevada, United States (two sites: JSJ and JSR); tropical Pacific (for large-scale climate drivers).
• Temporal Scale: Tree-ring chronologies spanning 1690–2022 (JSJ) and 1673–2022 (JSR); analysis of relationships strengthening/weakening in recent decades and peaking in the early 2000s.

Methodology and Data

• Models used: None explicitly mentioned; observational dendrochronology study with statistical correlation analyses.
• Data sources: Increment cores from Pinus jeffreyi (n = 21, site JSJ) and Abies magnifica (n = 44, site JSR); local climate variables (temperature, precipitation, drought); broad-scale ocean-atmosphere conditions (zonal and meridional winds, sea-level pressure, sea surface temperature); MJO indices.

Main Results

• Both Pinus jeffreyi (JSJ) and Abies magnifica (JSR) tree-ring records show significant correlations (p < 0.05) with local climate variables, particularly moisture availability.
• JSJ, located on a south-facing slope, exhibits markedly stronger connections with large-scale climate drivers, including zonal and meridional winds, sea-level pressure, and sea surface temperature, especially across the tropical Pacific.
• JSR, from a north-east facing slope, shows more localized climate responses.
• JSJ demonstrated significant correlations with multiple MJO indices (p < 0.01), marking the first documented link between MJO dynamics and tree-ring data.
• No significant MJO correlations were found for JSR.
• Relationships between JSJ and early MJO phases (1–3) have strengthened in recent decades, while those with later phases (6–8) peaked in the early 2000s but have since weakened, aligning with California's ongoing drought.
• The MJO is suggested to influence tree growth through its modulation of atmospheric rivers and precipitation patterns.

Contributions

• Provides the first published evidence of a Madden–Julian Oscillation (MJO) signal in tree rings.
• Offers the potential to develop a novel proxy for past MJO variability.
• Underscores the importance of understanding tropical–extratropical climate linkages and their impact on regional ecosystems, with implications for improving climate projections and managing water resources.

## Funding -

Citation

@article{Rhee2025Topographic,
  author = {Rhee, George and Thatcher, Diana L. and Warnick, Katarina J. and Carrell, Josh and Ford, Andrew and George, Jessie and Harris, Victoria and Lemis, Patrick and Radford, Alan M. and Maxwell, Richard and Harley, Grant L.},
  title = {Topographic Setting Drives the Imprint of the Madden–Julian Oscillation ( <scp>MJO</scp> ) on Tree Growth in the Northern Sierra Nevada},
  journal = {International Journal of Climatology},
  year = {2025},
  doi = {10.1002/joc.70162},
  url = {https://doi.org/10.1002/joc.70162}
}