ORCA-LIM experiments with the interannual Large & Yeager forcing Claus Böning, Arne Biastoch, Ulf Schweckendiek, Sabine Hüttl, Joke Lübbecke (IFM-GEOMAR, Kiel) with special thanks to our French colleagues collaborating in the DRAKKAR project

Examples of interannual-decadal variability in ORCA2 and ORCA05: Tropical oceans: EUC and STC-transports, SST ACC (Drake Passage) transport Atlantic MOC transport [Sea ice coverage] Question: effect of long-term drifts in the CNYF-runs ?

Tropical circulation: examples of spin-up behaviors (CORE-1) EUC transports Sv GFDL Pacific ORCA2 years ORCA2 Atlantic ORCA05

Pacific SST anomalies

CORE-2: Pacific SST variability (Nino3): ORCA05 , ORCA2 vs. Data

SST variability (Nino3-region) in ORCA05 vs. SOI index

Pacific Subtropical-Tropical overturning Cells (STCs): Equatorward transports across 10°N/10°S Sv ORCA05 ORCA2 robust trend ! (-14 Sv) shown here: Deviations from long-term means: 59 Sv (ORCA2), 67 Sv (ORCA05)

Atlantic: SST anomalies after 50 yrs spin-up (CORE-1)

SST variability (ATL4-region): ORCA05 vs. Reynolds

Atlantic STC-index (8°N/8°S) ORCA05 – ORCA05 – ORCA2 – FLAME(1/3) - trend: robust (+2 Sv) - year-to-year var.: differing - decadal variab. (> 5 yrs): fairly robust

ORCA2 and MICOM (W.Hazeleger, KNMI) Annual cycle of the EUC at 23°W (after 50-yr spin-up) ORCA2 and MICOM (W.Hazeleger, KNMI)

ORCA2 - MICOM - ORCA05

EUC (23°W) ORCA2 – MICOM - ORCA05 - FLAME1/12

Regarding simulations of tropical variability: CORE-II experiments help to identify where models are robust and where results are sensitive to model choices: - (inter-)decadal transport changes are very robust - seasonal-interannual variability: differs between realizations

Drake Passage transport (two ORCA05-cases)

Drake Passage transport anomalies (deviations from the climatological reference runs)

Atlantic MOC (45°N)

MOC anomalies (deviations from the climatological reference runs) ORCA05 – 3 realizations FLAME-1/3° ORCA2 ORCA05