Results from the NCAR CSM1.4- carbon model at Bern Thomas Frölicher Climate and Environmental Physics, Physics Institute, University of Bern 1.Modeled changes in oceanic dissolved oxygen 2. Ocean acidification CARBOOCEAN Core Theme V, Gran Canaria, December 5, 2006

Kim et al, MTS, 1999; Kim et al, GRL, /54  How large are simulated ocean O 2 changes in the NCAR CSM1.4-carbon model over the historical period and the future? Oxygen [μmol/kg] Depth [m] Motivation

Simulations with the NCAR CSM1.4-carbon Model physics: Fully coupled atmosphere(T31)-land-ocean-sea ice model low climate sensitivity (  T 2xCO2 = 1.4 K) Biogeochemistry model: Ocean carbon cycle model: modified OCMIP-2 prognostic nutrient uptake as function of light, Fe, PO 4, temperature Simulations: Forcing: solar + volcanic + GHG + direct sulfate prescribed land-use and fossil emissions (historical + SRES A2 + B1)

Heat uptake: Levitus (2005) vs. Model 0-300m m volcano

Sea-to-air O 2 flux is increasing CSM1.4-carbon: 0.25 mol m -2 yr -1 Bopp et al. (2002): 0.35 mol m -2 yr -1 Matear et al. (2000): 0.40 mol m -2 yr -1 positive values: outgassing B1 A2

O 2 -flux vs heat flux relationship 2000 – nmol J nmol J -1 Plattner et al. (2002): 5.9 nmol J -1 Bopp et al. (2002): 6.1 nmol J -1 Keeling et al. (2002) : 4.9 nmol J -1 Sarmiento et al. (1998): 6.0 nmol J -1

Modelled vs. observed changes in AOU Difference between 1990s and 1970s North Pacific (1990s s)

Locations of large O 2 changes over this century maximum decrease of O 2 maximum increase of O <-60 O2 [μmol/kg] > > O2 [μmol/kg] Depth [m] >

Conclusion The global air-to-sea O 2 flux is strongly correlated to the global air-sea heat flux. The O 2 /heat ratio is smaller than found in earlier studies. The simulated changes are qualitively comparable to the observations, but regionally too small. The oxygen concentration is projected to decrease over this century, mainly in the North Pacific and the Southern Ocean at shallow depths.

Projection of supersaturated water 1820 – 2100 (SRES A2) Ω A > 4: optimal 4 > Ω A > 3:adequate 4 > Ω A > 2:marginal 2> Ω A > 1: low Ω A < 1: extremely low Condition for coral calcification Volume [%]

Posters: O 2 (T. Frölicher, G.-K. Plattner, F. Joos) Ocean acidification (M. Steinacher, T. Frölicher, G.-K. Plattner, F. Joos) Thanks Thank you very much for your attention!

Difference DOM Export out of production zone ∆ ~ 8 %

Phospate in year 2000 CSM1.4-carbonWorld Ocean Atlas (2001) Atlantic 20° W Pacific 167° W

Export Production of POC CSM1.4-carbon Laws et al. (2000) Total: 9.2 Pg C Total: 11.1 Pg C ∆ ~ 17 %