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New transient runs for GCEP. Alan project meeting 18/11/08. Summary of runs. Flux corrected transient runs 1860 – present, 4-member IC ( δ SST) ensemble.

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New transient runs for gcep

New transient runs for GCEP


project meeting 18/11/08

Summary of runs
Summary of runs

  • Flux corrected transient runs 1860 – present,4-member IC (δSST) ensemble.

  • Previous transient runs may have contained “control drifts” due to ICs – this time start from end of 500-year control (in turn started from near end of HC’s 1000-year run).

  • Some drifts remain in control despite long spin-up. These are small (typical change per century: 0.005 PSU, -0.05K), even though at depth they exceed any faster variability.

Is the 1915 1945 moc decrease internal variability
Is the ~1915-1945 MOC decrease internal variability?

  • Compare MOC power spectrum with control run

  • Have lost control run on gorgon, but still have similar 500-year control run done for COAPEC

    • (currently messy to diagnose, as the netCDF files lack correct metadata to drive diagnostics package)

  • Obtain 3 x 146-year timeseries

    • can’t treat as IC ensemble (ICs differ by more than δ)

    • but can treat as 3 samples of control power spectrum, compare with spectra of transient ensemble members

Moc 45n power spectrum transient black and control blue
MOC 45N, power spectrum: transient (black) and control (blue)

Global upper ocean temperature surface to fixed depth 220m
Global upper-ocean temperature,surface to fixed depth (220m)

Global upper ocean temperature surface to isotherm 14c
Global upper-ocean temperature,surface to isotherm (14C)

Pacific decadal oscillation
Pacific Decadal Oscillation

First EOF of monthly SST (detrended, deseasonalised) 1900-1992 in box shownPlotted here: SST regressed on first PC, showing some correlated signals elsewhere

Pdo continued
PDO continued

  • Have EOF pattern that we can project other SST timeseries onto (e.g. other runs, or outside EOF analysis period) – should I incorporate into diagnostics package?

  • ‘bullseye’ in EOF pattern near Japan not seen in other studies but seems to be consistent area of high variability in these UM runs. (Why?)

  • Can we relate PDO timeseries to upper ocean heat content? (Keith to explain?)