Pacific–Antarctic Ridge Meander Analysis

This repository provides the datasets, MATLAB functions, and figures used in the analysis of the characteristics and long-term trends of the Pacific–Antarctic Ridge (PAR) meander in the Southern Ocean over the 1993–2023 period.

The analyses combine satellite altimetry, RG Argo climatology, and CMEMS surface geostrophic velocities to document meander structure, variability, and associated eddy kinetic energy (EKE).

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Repository structure

Core analysis repositories

• meander_loc_mon_1993_2023_mean_199303_202303
  Contains monthly mean meander positions for 1993–2023 derived from altimetry with probability-based frontal detection.

• meander_monthly_locations_north_south_boundaries
  Provides the north/south latitude boundaries of the meander, enabling calculation of meander width and variability across longitude.

• pacific_antarctic_ridge_meander_analysis (this repository)
  Includes diagnostic MATLAB scripts and functions for processing, trend estimation, and figure generation.

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Key MATLAB functions

Gyre and Argo

• 01-PAR-Argo-Temperature-2004-2023-Build-4D-Cube.m
  Constructs 4-D absolute temperature fields (time × lon × lat × pressure) from RG Argo mean + anomalies (2004–2023), concatenates monthly NetCDF inputs, and saves MATLAB datasets.

• 02-CMEMS-Gyre-ADT-TimeSeries-Trend-1993-2023.m
  Builds an area-mean monthly ADT anomaly time series for the subtropical gyre (42°–38°S, 150°E–70°W), deseasons it, and computes linear and non-parametric trends (Sen, MK, modified MK, OLS).

EKE and geostrophic currents

• 04-PAR-CMEMS-EKE-Trend-Analysis-1993-2023.m
  Concatenates CMEMS ugos/vgos files (1993–2023), produces monthly running-mean velocity fields, derives eddy kinetic energy (EKE), maps its 1993–2023 mean, estimates decadal EKE trends, and extracts section-based time series with Sen/MK diagnostics.

Meander dynamics

• 05-Meander-Width-Speed-Trend-Decomposition.m
  Tests whether meander widening is explained by along-jet speed strengthening. Performs width–speed regression, decomposes width trends into explained and residual parts, and outputs publication-quality figures of raw, explained, and residual trends.

Statistical tools

• 03-Mann-Kendall-Trend-Test.m
  Classical Mann–Kendall test for monotonic trends. Returns hypothesis test decision, p-value, and S statistic.

• 06-Modified-Mann-Kendall-Trend-Test.m
  Modified Mann–Kendall test (Hamed & Rao, 1998) with autocorrelation adjustment. Provides robust trend significance for autocorrelated series.

• 08-Theil-Sen-Slope.m
  Theil–Sen slope estimator (median of pairwise slopes). Robust trend slope estimate used throughout the repository.

Plotting helpers

• 07-Plot-TimeSeries-With-Trend.m
  Generates time series plots with Sen slope lines, Mann–Kendall significance annotations, and publication-ready formatting.

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Figures

Figures produced with these functions illustrate:

• Meander position and trajectory from altimetry,
• Meander width and intensity variability (north/south boundaries),
• Trends in along-jet geostrophic current speed,
• Eddy kinetic energy (EKE) patterns and changes,
• Temperature structure from RG Argo climatology.

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License

MIT License — free to use, modify, and share with attribution.