Overview
The National Science Foundation funded Simple Ocean Data Assimilation (SODA) project provides retrospectively integrated, spatially complete reconstructions of the global historical ocean climate. The project goal is to provide a uniform, continuous picture of the evolving global ocean/sea ice system beginning January, 1980.
The latest iteration, SODA4 (specifically the soda4.15 stream series), represents a critical step forward from the eddy-permitting 0.25° architecture of SODA3. SODA4 introduces a global eddy-resolving 0.1° horizontal resolution, allowing for accurate mapping of near-shore environments, shallow coastal processes, and narrow currents dominated by intense flow instabilities and mesoscale signals.
The version uses sparse physical oceanic/sea ice observations (including satellite SST, sea ice concentrations, and in situ temperature and salinity profiles) as physical constraints to guide the evolution of high-resolution numerical ocean models. Constraints are applied via an advanced optimal interpolation (OI) data assimilation algorithm driven by high-frequency atmospheric configurations.
Dataset Metadata
| Data Type | Gridded mesoscale ocean/sea ice reanalysis variables (NetCDF-4 format) |
|---|---|
| Temporal Range | 45-year continuous timeline: 1980 – 2024 |
| Horizontal Resolution | 0.1° x 0.1° global grid (~10km at the equator; eddy-resolving) |
| Vertical Resolution | Enhanced vertical resolution ocean layers |
| Numeric Numerics | GFDL MOM5 Ocean Model / SIS1 Sea Ice Numerics |
| Surface Forcing | ECMWF ERA5 (Internal reference forcing stream: 15) |
| Assimilation Method | Optimal Interpolation (OI) sequential analysis algorithm |
| Observational Constraints | Satellite SST, In situ T/S profiles (WOD/Argo), and Sea Ice Concentration properties |
Data Structure & Variables
SODA4 output fields exhibit reduced bias, enhanced regional variability, and minimized observational footprint artifacts compared to sparse unassimilated grids. Files are delivered at multi-day intervals packed with essential diagnostic parameters:
| Ocean Dynamics | Potential Temperature (temp), Salinity (salt), Horizontal Zonal Velocity (u), Meridional Velocity (v), Sea Surface Height (ssh) |
|---|---|
| Sea Ice Diagnostics | Sea Ice Concentration / Fractional Area (aice), Sea Ice Thickness (hice) |
| Flux Parameters | Net Surface Heat Flux Adjustments, Freshwater / Bias Corrected boundary increments |
Download Data
Select a specific reanalysis year below to access the multi-day diagnostic output files:
Automated Command Line Download
For batch downloads across a specified range within the 1980–2024 period, use the following bash approach:
# Example script to download SODA4 netCDF output blocks via terminal
for year in {1980..2024}; do
wget https://www2.atmos.umd.edu/~carton/soda4/DATA/soda4.15_${year}.nc
done
Citations & Contact
When using this dataset for publications, research, or process studies, please use the following primary scientific reference:
Chepurin, G. A., Carton, J. A., Sun, L., and Penny, S. G.: SODA4: a mesoscale ocean/sea ice reanalysis 1980–2024, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-3810, 2025.
Contact and Inquiries
For feedback, questions regarding data availability, or specific anomalies in high latitude configurations, please contact:
Dr. James A. Carton
Department of Atmospheric and Oceanic Science
University of Maryland, College Park, MD 20742
Email: carton@atmos.umd.edu