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, 2002

1996

1979 1969

1932/54

How large are simulated ocean O2 changes in the NCAR

CSM1.4-carbon model over the historical period and the future?

200 240 280 3200

1000

2000

3000

4000

Oxygen [μmol/kg]D

ep

th [m

]

Motivation

Simulations with the NCAR CSM1.4-carbon

Model physics:

• Fully coupled atmosphere(T31)-land-ocean-sea ice model

• low climate sensitivity (T2xCO2 = 1.4 K)

Biogeochemistry model:

• Ocean carbon cycle model: modified OCMIP-2

• prognostic nutrient uptake as function of light, Fe, PO4, 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

0-3000m

volcano

Sea-to-air O2 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

O2-flux vs heat flux relationship

2000 – 2100

1820-2000

4.4 nmol J-1

3.2 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 - 1970s)

Locations of large O2 changes over this centurymaximum decrease of O2

maximum increase of O2

0

-20

-40

<-60

O2 [μmol/kg]>30

24

16

8

0

>4000

3200

2400

1600

800

0

O2 [μmol/kg]

Depth [m]Depth [m]

>4000

3200

2400

1600

800

0

Conclusion

• The global air-to-sea O2 flux is strongly correlated to the global

air-sea heat flux. The O2/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)

ΩA > 4: optimal

4 > ΩA > 3: adequate

4 > ΩA > 2: marginal

2> ΩA > 1: low

ΩA < 1: extremely low

Condition for coral calcification

1850 2000 2100

100

96

92

90

0

40

Vo

lum

e [%

]

Posters:

• O2 (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!

froelicher@climate.unibe.ch

Difference 2100 - 1820

DOM Export out of production zone

1820 -2100

∆ ~ 8 %

Phospate in year 2000CSM1.4-carbon World Ocean Atlas (2001)

Atlantic20° W

Pacific167° W

Export Production of POC

CSM1.4-carbon

Laws et al. (2000)

Total: 9.2 Pg C

Total: 11.1 Pg C

∆ ~ 17 %