⚠️ Inconsistent ocean and sea ice in final 7.5yr of 0.1° IAF cycle 4

COSIMA
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16

Wondering what we should do about this.

To summarise:

  • 01deg_jra55v140_iaf_cycle4 had a non-reproducible glitch at roughly 2011-09-27
    • This seems to have been a tiny initial perturbation, but the difference eventually became macroscopic due to chaos.
    • I think the ocean data is therefore credible, since it’s just another realisation of turbulence from the same statistical distribution; the glitch was possibly as insignificant as the (reproducible) roundoff errors that happen all the time.
    • We don’t know how often these non-reproducible glitches happen (since they are only detected if we re-run) so there may be several other examples of this issue in our datasets (we know there was another case in cycle 3 affecting all subsequent cycles).
  • The main problem is we don’t have any sea ice data (except 6-hourly) that is consistent with the 01deg_jra55v140_iaf_cycle4 ocean data from 2011-09-27 onwards, and we can’t generate it due to the non-reproducible glitch in the original run.
    • the post-2002 non-6-hourly sea ice data in 01deg_jra55v140_iaf_cycle4 was actually generated by 01deg_jra55v140_iaf_cycle4_rerun_from_2002, and is inconsistent with the ocean state from 2011-09-27 onwards