18-eddy-wind-work
Supplied working report; original verdicts not validated.
Review status: Needs review. This is an archival source note, not a passed proof.
REPORT.md
# 18 — Eddy Energy Tracks Wind Work (`eddy-wind-work`)
- Source: Incoprea Theory, Volume XXIX (`eddy-wind-work`)
- Claim: Ocean eddy kinetic energy tracks wind work at the same latitudes rather than stored potential energy.
- Prediction: Energy should track wind work.
- Refutation: Energy tracking stored potential would remove forcing.
## Test performed
Literature-led assessment (evidence class b), using primary papers on the ocean energy cycle and on Southern Ocean eddy/altimetry trends, plus a transcription of their published numbers into small CSVs and a figure ([data/ocean_energy_cycle.csv](data/ocean_energy_cycle.csv), [data/southern_ocean_eke_trends.csv](data/southern_ocean_eke_trends.csv), [data/southern_ocean_wind_eke_relationships.csv](data/southern_ocean_wind_eke_relationships.csv), [figures/eddy_wind_energy.png](figures/eddy_wind_energy.png)). Direct AVISO downloading was avoided (too heavy); numbers come from the papers' abstracts, summaries and tables as published. Two questions were asked: (1) does EKE energy come from wind work or from stored potential energy (the energy cycle), and (2) do observed EKE changes track wind changes (the trend data).
## Data (sources, URLs, sample sizes)
- Wunsch 1998, *J Phys Oceanogr* 28:2332–2340 — TOPEX/Poseidon altimetric estimate of wind work. https://journals.ametsoc.org/view/journals/phoc/28/11/1520-0485_1998_028_2332_twdbtw_2.0.co_2.xml
- von Storch et al. 2012, *J Phys Oceanogr* 42:2185–2196 — Lorenz energy cycle from the 1/10° STORM/NCEP simulation (multidecadal, 6-hourly forcing). https://journals.ametsoc.org/view/journals/phoc/42/12/jpo-d-12-079.1.xml
- Meredith & Hogg 2006, *GRL* 33:L16608 — satellite altimeter EKE + SAM analysis, eddy-resolving model. https://nora.nerc.ac.uk/id/eprint/84/ (DOI: 10.1029/2006GL026499)
- Hogg et al. 2015, *JGR Oceans* 120:257–267 — updated satellite altimetry EKE record (~1993–2012) + idealized model perturbation experiments. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014JC010470 (open PDF: https://nora.nerc.ac.uk/id/eprint/509239/) — note: the notebook cites this as "Nature Geoscience"; the paper with this title and these authors is the JGR Oceans article.
- Ferrari & Wunsch 2009, *Annu Rev Fluid Mech* 41:253–282 (standard review, paywalled; used as background) — https://doi.org/10.1146/annurev.fluid.010908.165205
## Result (key numbers; reference figure files)
**Energy cycle — where EKE energy actually comes from.** In the STORM/NCEP ocean energy cycle (von Storch et al. 2012): total power input to the ocean is 6.6 TW (~4 TW from winds, rest from surface buoyancy); the reservoirs are mean KE 1.3 EJ, eddy KE 3.5 EJ, eddy available potential energy (APE) 6.4 EJ. "Baroclinic instability is the main mechanism in converting the mean available potential energy into the eddy kinetic energy in the ocean. The total rate of this conversion amounts to 0.7–0.8 TW." Wind work enters the **mean** flow: the wind-generated energy is "distributed" via a 0.5 TW mean-KE → mean-APE conversion, and only ~0.1 TW converts from mean KE directly to EKE. In short, EKE is fed by the release of **stored available potential energy** (the sloping isopycnals of the wind- and buoyancy-forced circulation), not by local wind work; wind is the ultimate external driver acting through the mean flow and the APE reservoir. Wunsch 1998 estimated wind work on the general circulation at ~1 TW, "dominated by the work done by the mean zonal wind in the Southern Ocean," consistent with the wind input feeding the circumpolar current whose baroclinic instability then generates EKE.
**Trend data — does EKE co-vary with wind?** Partially yes, but not as simple local tracking. Meredith & Hogg 2006 found anomalously high ACC EKE in 2000–2002 lagging the 1998 positive SAM (wind-stress) peak by **2–3 years**, a lag they attribute to the time needed to spin up the deep ACC circulation — i.e., the response is mediated by the circulation's stored energy, not instantaneous local wind work. Hogg et al. 2015 found EKE increased over ~1993–2012 (Pacific +14.9±4.1, Indian +18.3±5.1, Atlantic +4.0±3.7 cm² s⁻² per decade; 90% CI) while ACC transport did **not** increase (probable slight decrease) — "eddy saturation." Their model experiments attribute the decadal EKE rise to continuing wind-stress increases, but ACC transport correlates with wind stress only at periods <10 years and is weakly affected at longer periods. So EKE tracks wind forcing at interannual-to-decadal scale only through the eddy-mean-flow balance (energy stored in the APE reservoir), and saturates rather than tracking wind work one-to-one.
**Same-latitude question.** Wind work is concentrated in the Southern Ocean westerlies (Wunsch 1998), and zonal-mean EKE is also largest in the ACC band — a broad co-location that superficially matches the claim. But the causal chain at those latitudes is wind → mean flow/APE (Ekman-driven isopycnal tilt) → baroclinic instability → EKE (von Storch 2012). EKE hotspots elsewhere (western boundary current extensions) are likewise fed by APE release from the gyre circulation, not by local wind-work maxima.
## Verdict
**Not supported** — the ocean energy cycle shows EKE is generated from stored available potential energy via baroclinic instability (0.7–0.8 TW conversion, von Storch et al. 2012), exactly the pathway the hypothesis excludes ("rather than stored potential energy"); wind work (~1–4 TW) enters the mean flow and reaches EKE only indirectly, and observed EKE responses to wind changes lag by 2–3 years and saturate (Meredith & Hogg 2006; Hogg et al. 2015). The claim is not wholly wrong — wind is the ultimate external driver and decadal Southern Ocean EKE trends do follow wind-stress trends — but "tracks wind work at the same latitudes rather than stored potential energy" inverts the actual energy pathway.
## Limitations
- No new AVISO computation was performed (dataset too heavy per instructions); the assessment uses published altimetry-derived numbers from the papers' own analyses.
- "Tracking" is ambiguous (co-variation vs energy source); the verdict addresses the mechanism reading of the claim, which is the one its refutation criterion ("energy tracking stored potential would remove forcing") invites.
- The Hogg et al. 2015 trends are over one ~20-year altimetry record; attributing decadal EKE trends to wind stress rests partly on idealized models.
- Energy-cycle numbers come from a single high-resolution model (STORM/NCEP) and depend on the APE reference state; magnitudes are approximate (0.7–0.8 TW conversion vs ~3 TW EKE dissipation implies additional EPE sources such as buoyancy-driven generation, which von Storch discuss).
## References
- von Storch et al. 2012, *J Phys Oceanogr* 42:2185–2196. https://journals.ametsoc.org/view/journals/phoc/42/12/jpo-d-12-079.1.xml
- Wunsch 1998, *J Phys Oceanogr* 28:2332–2340. https://journals.ametsoc.org/view/journals/phoc/28/11/1520-0485_1998_028_2332_twdbtw_2.0.co_2.xml
- Meredith & Hogg 2006, *GRL* 33:L16608. https://doi.org/10.1029/2006GL026499 (abstract: https://nora.nerc.ac.uk/id/eprint/84/)
- Hogg et al. 2015, *JGR Oceans* 120:257–267. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014JC010470 (PDF: https://nora.nerc.ac.uk/id/eprint/509239/)
- Ferrari & Wunsch 2009, *Annu Rev Fluid Mech* 41:253–282. https://doi.org/10.1146/annurev.fluid.010908.165205
All URLs accessed 30 October 2026.