Persch et al. (2025) A Critical Role for North Pacific Meridional Mode in the ENSO Response to Orbital Precession

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

Identification

• Journal: Journal of Climate
• Year: 2025
• Date: 2025-09-09
• Authors: Cole Persch, Sara C. Sanchez
• DOI: 10.1175/jcli-d-25-0065.1

Research Groups

• National Center for Atmospheric Research (NCAR)

Short Summary

This study investigates how orbital precession influences El Niño–Southern Oscillation (ENSO) variability through the Pacific meridional mode (PMM) using climate model simulations. It finds that precession strongly modulates PMM variability, its effectiveness in triggering El Niño events, and ENSO diversity, primarily driven by changes in surface wind fields affecting the wind–evaporation–sea surface temperature (WES) feedback.

Objective

• To examine how orbital precession influences El Niño–Southern Oscillation (ENSO) variability through a subtropical pathway, the Pacific meridional mode (PMM).
• To investigate mechanisms (midlatitude stochastic forcing, climatological mean state changes, WES feedback) that may moderate the PMM's influence on ENSO under different precessional extremes.

Study Configuration

• Spatial Scale: Pacific basin, encompassing tropical and subtropical regions, including the intertropical convergence zone (ITCZ) and North Pacific.
• Temporal Scale: Millennial time scales, examining five precessional extremes (perihelion at autumnal equinox, winter solstice, vernal equinox, summer solstice, and zero eccentricity).

Methodology and Data

• Models used: NCAR Community Earth System Model, version 1.2 (CESM1.2)
• Data sources: A suite of CESM1.2 experiments simulating five precessional extremes.

Main Results

• Orbital precession strongly influences PMM variability, the PMM’s ability to trigger El Niño events, and ENSO diversity.
• Precessional extremes characterized by a more southerly ITCZ and stronger trade winds (winter solstice and autumnal equinox) exhibit more variable PMM behavior and a PMM that is more effective at triggering El Niño events, particularly central Pacific events.
• Precessional extremes characterized by a more northerly ITCZ and weaker trade winds (summer solstice and vernal equinox) show reduced PMM variability and a PMM that is a less reliable precursor to El Niño events.
• The PMM response to precession is driven by variations in surface wind fields that moderate the strength of the wind–evaporation–sea surface temperature (WES) feedback, which is the mechanism for PMM anomaly growth and propagation.

Contributions

• Demonstrates a direct link between orbital precession and ENSO variability mediated by the Pacific meridional mode (PMM).
• Identifies surface wind fields and the WES feedback as key mechanisms through which precession modulates PMM behavior and its influence on El Niño.
• Provides insights into how subtle shifts in the mean climate state, driven by external forcing, can alter the characteristics and diversity of ENSO events.
• Offers a framework for interpreting past climate variability and anticipating future changes in the tropical Pacific's sensitivity to external forcing.

Funding

• Not specified in the provided abstract.

Citation

@article{Persch2025Critical,
  author = {Persch, Cole and Sanchez, Sara C.},
  title = {A Critical Role for North Pacific Meridional Mode in the ENSO Response to Orbital Precession},
  journal = {Journal of Climate},
  year = {2025},
  doi = {10.1175/jcli-d-25-0065.1},
  url = {https://doi.org/10.1175/jcli-d-25-0065.1}
}