Xu et al. (2025) Seasonality of the South Pacific Meridional Mode: Role of Oceanic Meridional Advection Feedback Beyond Thermodynamics Dominance

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

Identification

• Journal: Geophysical Research Letters
• Year: 2025
• Date: 2025-12-05
• Authors: Juying Xu, Hanjie Fan, Song Yang, Yuhao Cai, Matthew Collins, Weidong Yu
• DOI: 10.1029/2025gl117920

Research Groups

Not specified in the abstract.

Short Summary

This study investigates the seasonality of the South Pacific Meridional Mode (SPMM), revealing that while thermodynamical wind-evaporation-SST feedback drives SPMM-SST growth, meridional advection, primarily from wind stress-driven Ekman transport, acts as a dominant damping mechanism, critically shaping its seasonal cycle.

Objective

• To clarify the seasonality of the South Pacific Meridional Mode (SPMM), specifically the out-of-phase relationship between its sea surface temperature (SST) (peaking in December–February) and wind (peaking in June–August) indices.

Study Configuration

• Spatial Scale: Subtropical southeastern Pacific Ocean (regional scale).
• Temporal Scale: Seasonal (December–February, June–August) to interannual variability.

Methodology and Data

• Models used: Mixed-layer heat budget analysis framework.
• Data sources: Not specified in the abstract.

Main Results

• Thermodynamical wind-evaporation-SST feedback is the dominant mechanism for SPMM-SST growth, with its efficiency controlled by the seasonal cycle of mixed-layer depth.
• Dynamical processes, particularly meridional advection, suppress SPMM-SST anomalies, acting as the dominant damping mechanism in both June–August (JJA) and December–February (DJF), and being especially strong in JJA.
• Stronger meridional advection damping during JJA contributes to enlarging the DJF peak of SPMM-SST, highlighting a role beyond pure thermodynamics.
• The meridional advection is largely attributed to wind stress-driven Ekman transport.

Contributions

• Provides a comprehensive understanding of the physical mechanisms governing SPMM seasonality, particularly the interplay between thermodynamic feedback and dynamic damping.
• Highlights the critical importance of meridional advection, driven by Ekman transport, in shaping the SPMM seasonal cycle.
• Offers new insights for improving the predictability of SPMM-related climate variability.

Funding

Not specified in the abstract.

Citation

@article{Xu2025Seasonality,
  author = {Xu, Juying and Fan, Hanjie and Yang, Song and Cai, Yuhao and Collins, Matthew and Yu, Weidong},
  title = {Seasonality of the South Pacific Meridional Mode: Role of Oceanic Meridional Advection Feedback Beyond Thermodynamics Dominance},
  journal = {Geophysical Research Letters},
  year = {2025},
  doi = {10.1029/2025gl117920},
  url = {https://doi.org/10.1029/2025gl117920}
}