1. Anthropogenic carbon in a varying ocean Fortunat Joos, Thomas Fröhlicher Climate and Environmental Physics, Physics Institute, University of Bern www.climate.unibe.ch/~joos CARBOOCEAN Meeting Bremen, December, 2006 Thanks to C. Lo Monaco, A. Velo and co-workers to the MPI and IPSL modelling groups

2. Data from the past show that anthropogenic climate change is proceeding at high speed

3. (IPCC, 2007, Fig. TS-2a ) Time (years before present) CO 2 versus Antarctic Temperature 020000 10000 The atmospheric concentration of carbon dioxide in 2005 exceeds by far the natural range over the last 650,000 years (180 to 300 ppm) as determined from ice cores (IPCC, SPM, 2007). Natural Range

4. What about rates of change?

5. The rate of increase in the combined radiative forcing from CO 2, CH 4 and N 2 O during the industrial era is very likely to have been unprecedented in more than 10,000 years (SPM, 2007) (IPCC, 2007, Fig. TS-2 )

6. (Joos and Spahni, PNAS, submitted) The age distribution of air enclosed in ice Greenland CH 4 Antarctic (Dome C), today Antarctic (Dome C), Last Glacial Maximum

7. (Joos and Spahni, PNAS, submitted) The rate of increase in the combined radiative forcing from CO 2, CH 4 and N 2 O during the industrial era is very likely to have been unprecedented in more than 10,000 years (IPCC, SPM, 2007) Rates of Change over the past 22,000 years

8. Models and system understanding: current carbon emissions will affect the climate for many millennia

9. Long-term CO 2 and sea level committment in EMICs 1820 -2100 200025003000 200025003000 Year 60% 0 Atmosphere Ocean Land 2000 GtC Thermal Expansion (m) 1 IPCC AR4 EMIC Intercomparison Plattner et al., J.Clim., 2007; Cumulative Emissions 0%

10. IPCC Scenario Meeting, Sep 2007 A new set of emission mitigation and baseline scenarios Four scenarios to be selected for AOGCM runs → use in CARBOOCEAN

11. (Van Vuren et al., submitted) Cumulative carbon emission in multi-gas mitigation scenarios

12. Projected CO2 in 2100 Baseline Mitigation 650 to 950 ppm 380 to 620 ppm (Van Vuren et al., submitted)

13. A new set of mitigation scenarios is available van Vuren et al., In preparation

14. (Van Vuren et al., submitted) Baseline Mitigation Radiative Forcing (W m -2 ): 6 to 10 2.4 to 5.1 CO2 (ppm): 650 to 950 380 to 620 Projected Radiative Forcing in 2100

15. (Van Vuren et al., submitted) Baseline Mitigation 2.6 to 4.6°C 1.1 to 2.4°C Projected Temperature Change (1990 to 2100)

16. Are there critical thresholds...?

17. . Ocean Acidification and Aragonite Saturation Observation- based NCAR CSM1.4 supersaturation AA 2 1 4 3 0 AA 2 1 4 3 0 (Steinacher, 2007)

18. . Observation-based Aragonite Saturation in the Atlantic NCAR CSM1.4 supersaturation 0 10 20 -10  CO 3 — [mol/m 3 ] 1000 4000 0 depth [m] 90 o S90 o N (Steinacher, 2007)

19. Evolution of Aragonite Saturation in the Surface Surface pCO 2 (ppm) Latitude 90 o S 90 o N 300500700 supersaturation AA 2 1 4 3 0 (Steinacher, 2007)

20. Fluxes of calcite and aragonite to depth CaCO3 flux in PISCES (PgC/m2/y) Aragonite Calcite Total CaCO 3 Gangsto, in prep. CaCO 3 Flux (PgC/yr) Depth (m) 0 5000 Total CaCO 3 Calcite Aragonite Will dissolution of shallow aragonite sediments mitigate some of the ocean acidification signal? Magnitude? Time scales? 00.8 0.4

21. 460 ppm: Arctic Ocean becomes undersaturated with respect to Aragonite 560 ppm: Antarctic surface waters become undersaturated 560 ppm: surface water that is more than 3 times oversaturated dissappears Conclusions: Ocean Acidification

22. How well do different reconstruction methods of Canth work in the AOGCM model world?

23. a) Canth simulated by model b) Canth reconstructed from simulated tracers (C, Alk, O 2,...) Simulated and reconstructed Canth should be identical

24. a) Canth simulated by model

25. . NCAR CSM1.4 Surface Temperature and CO 2 for SRES A2 and B1 190020002100 Year 300 500 700 CO 2 (ppm) 0 1 2  T ( o C) A2 B1 A2 B1 Anthropogenic forcing - Fossil and land use CO 2 emissions - CH 4, N 2 O, CFCs - direct sulphate aerosols Natural forcing - solar irradiance - stratospheric volcanic aerosols 190020002100 Year Instrumental Data

26. . Oxygen in the Atlantic, 20 W depth 90 o N 80 o S O2 (  mol-C/kg), NCAR 80 o N 200 400 0

27. . Observation-based (GLODAP) Anthropogenic CO 2 NCAR CSM1.4 Canth (mol m -2 ) 0 50 100

28. Change in decadal-mean PO 4 from 1820 to 2000 AD, Atlantic, 20 W Depth (m) 80 o S 60 o N 0 40  PO 4 *117 (  mol-C/kg) -40 0 4500 No century-scale trends decadal variability in high latitudes of NA

29. Modelled evolution of DIC and Canth for an individual grid cell (60 N, 20 W) Remove natural variability in DIC by splining to get Canth DIC (mmol/m 3 ) Time Canth DIC 2180 2100 1850 20001900 1950

30. Canth in the Atlantic along 20 W NCAR CSM1.4, 1994 Depth (m) 80 o S60 o N 30 70 0 Canth (  mol-C/kg) -10 0 5000

31. b) Canth reconstructed from simulated tracers (Carbon, Alk, O 2,...)

32. The TrOCA method as an example The usual assumptions - Fixed Redfield ratios to correct for remineralisation - No century-scale trends - time-invariant air-sea disequilibrium „Organic Matter Remineralization“ „CaCO3 dissolution“ Total Carbon „preindustrial Total Carbon“

33. Canth in the Atlantic along 20 W TrOCA with NCAR output, 1994 Depth (m) 0 Canth (  mol-C/kg) 80 o S60 o N 0 5000 70 30 -10

34. a) Canth simulated by model b) Canth reconstructed from simulated tracers (T, S, O2,...) Are simulated and reconstructed Canth identical?

35. TrOCA-NCAR „truth“, NCAR-Model 0 70 -10 (  mol-C/kg)

36. Potential Problems

37. Oxygen in NCAR TrOCA Remineralisation of organic matter does not consume O 2 in oxygen minimum zones (OCMIP Protocoll) Remineralisation and Canth is overestimated in reconstruction

38. Anoxic remineralisation of organic matter may bias Canth estimates

39. TrOCA-MPI „truth“, MPI Model 0 70 -10 (  mol-C/kg)

40. TrOCA-MPI Century-scale Trend in PO 4 in MPI Model Negative Canth in deep ocean

41. Century-scale trends may bias Canth estimates

42. What about interannual and decadal variability?

43. Internal Variability in AOU sdv of decal averaged AOU (  mol/kg) Frölicher et al., in prep. 5 3 0 2 1 4

44. The impact of volcanic forcing on global mean AOU and O 2 Frölicher et al., in prep. 100 1500 Depth (m) -  AOU O2O2 1960200019602000 Year Optical Depth

45. The impact of volcanic forcing on global meanO 2 and AOU Frölicher et al., in prep. 100 1500 Depth (m) -  AOU O2O2 1960200019602000 Year

46. . Oxygen in the Atlantic, A16N O2 (  mol-C/kg), NCAR 200 400 0

47. . Oxygen in the Atlantic, 20 W depth 90 o N O2 (  mol-C/kg), NCAR 200 400 0

48. . Internal Variability in DIC and in  C* from a control run in top 2000 m depth (  mol-C/kg) -4 4 Levine et al., in press 60 o S80 o N 1 , DIC  C* 0 60 o S80 o N -15 15 0

49. . Difference between modeled and reconstructed Canth for the  C* method 0 -15 15 Levine et al., in press Modelled increase over 10 year Difference (model-reconstruction) 60 o S80 o N (  mol-C/kg)

50. Both externally-forced and internal variability may bias Canth estimates

51. Other potential problems? Parameters of reconstruction method have not been determined with model output Fixed Redfield ratios assumed in model – correct?

52. How do results from different methods compare with modeled Canth?

53. Reconstruction methods: TrOCA (Touratier et al.)  C T 0 (Vazquez-Rodriguez; adjusted C* method) C T 0 IPSL: (Lo Monaco; back-calculation method, uses different preformed relationships for southern and northern water)

54. TrOCA „Truth“: NCAR Model CT0CT0 IPSL 0 70 -10 (  mol-C/kg)

55. Difference between simulated and reconstructed Canth, 20 W,1994 (  mol-C/kg) 50 0 -50 Depth (m) 0 5000 60 o N80 o S TrOCA

56. Difference between simulated and reconstructed Canth, 20 W,1994 (  mol-C/kg) 50 0 -50 Depth (m) 0 5000 60 o N80 o S CT0CT0

57. Difference between simulated and reconstructed Canth, 20 W,1994 (  mol-C/kg) 50 0 -50 Depth (m) 0 5000 60 o N80 o S IPSL

58. Conclusions Significant deviations between predicted and reconstructed Canth are found for all methods Potential biases: - externally-forced and internal variability - anoxic remineralisation - century-scale trends in watermasses/tracers - deviations from fixed Redfield ratios - parameters not determined with model output (IPSL Reconstruction Method)

59. . Oxygen in the Atlantic, 20 W depth 90 o N 80 o S O2 (  mol-C/kg), NCAR 80 o N 200 400 0

60. . Oxygen in the Atlantic, 20 W depth 90 o N 80 o S O2 (  mol-C/kg), NCAR 80 o N 200 400 0

61. . Oxygen in the Atlantic, 20 W depth 90 o N 80 o S O2 (  mol-C/kg), NCAR 80 o N 200 400 0

62. . Oxygen in the Atlantic, 20 W depth 90 o N 80 o S O2 (  mol-C/kg), NCAR 80 o N 200 400 0

63. . Oxygen in the Atlantic, 20 W depth 90 o N 80 o S O2 (  mol-C/kg), NCAR 80 o N 200 400 0

64. DIC in the Atlantic,1994, 20 W

65. PO4 in the Atlantic, 20 W

66. Canth in the Atlantic, 20 W

67. in the Atlantic, 24 N

68. in the Atlantic, 20 W 1994

69. in the Atlantic, 20 W 1994

70. PHICT in the Atlantic, 20 W

71. PHICT in the Atlantic, 24 N

72. TROCA in the Atlantic, 20 W

73. TROCA in the Atlantic, 24 N

74. in the Atlantic, 20 W

77. What ist the impact of 1. temperature distribution 2. organic matter export 3. CaCO 3 export on DIC and atm. CO 2 ? Apply a model to discriminate the mechanisms

78. Dead ocean with T=18 o C (present day carbon inventory in ocean-atmosphere system) Uniform distribution of DIC pCO 2 (atm) = 560 ppm AtlanticSouthern OceanPacific Depth DIC (mmol/m 3 )

79. Temperatures in the World Ocean

80. 1. Solubility and carbon chemistry: cold water holds more DIC than warm water → DIC concentration in the (warm) surface are on average depleted with respect to the (cold) deep ocean → atmospheric CO2 is lower compared to an ocean with a uniform temperature of T=18 o C

81. Dead ocean with present temperature distribution (present-day carbon inventory in ocean-atmosphere system) Surface water somewhat depleted in DIC pCO 2 (atm) = 439 ppm Depth AtlanticSouthern OceanPacific DIC (mmol/m 3 )

82. 2. Marine biota removes carbon from surface waters and this carbon is exported to the deep → DIC and nutrient concentrations in the surface are on average depleted with respect to the deep ocean → atmospheric CO 2 is lower compared to a dead ocean

83. The marine organic carbon cycle

84. Vertical distribution of tracers in the North Pacific Redfield ratio: P:N:C:O2 = 1:16:120:-170

85. Observed distribution of phosphate Surface water in the Atlantic and Pacific are depleted in nutrients by biological activities Depth AtlanticSouthern OceanPacific (mmol/m 3 )

86. Ocean with organic matter production and temperature distribution (but no calcite production) Surface water depleted in DIC pCO 2 (atm) = 229 ppm Depth AtlanticSouthern OceanPacific DIC (mmol/m 3 )

87. 3. Production and export of CaCO 3 increases the partial pressure of CO 2 in surface waters → A range of marine organisms form shells made of CaCO 3 Ca ++ + 2 HCO 3 - → CaCO 3 + CO 2 + H 2 O → Decrease in DIC, but shift in the ratio between different carbonate species → Alkalinity ~ [HCO 3 - ]+2 [CO 3 -- ] is decreasing → [H 2 CO 3 *] in the surface and atmospheric CO 2 is increased compared to an ocean without calcifying organisms

88. Observed distribution of potential Alkalinity Surface water is depleted in alkalinity Depth Pot. Alk (mmol/m 3 ) AtlanticSouthern OceanPacific

89. Observed distribution of DIC Surface water depleted in DIC and in alkalinity pCO 2 (atm) = 278 ppm Depth DIC (mmol/m 3 ) AtlanticSouthern OceanPacific

90. Regulation of atmospheric CO 2 Dead ocean with uniform T of 18 o C: 560 ppm Realistic temperature distribution:439 ppm + organic matter export229 ppm + CaCO 3 export278 ppm

91. Greenland and Antarctic temperature, CO 2 and CH 4 over the last transition Stauffer, Monnin, Blunier and co-workers, 2003 Past changes indicate the magnitude of potential future feedbacks

92. „Surprises in the Climate System“? Projected strenght of the North Atlantic overturning Cubasch et al., 2001

93. From the past to the future Indermühle et al, 1999 NADW collapse: limited impact on atmospheric CO 2 and ocean uptake CO 2 varies by up to 20 ppm during D/O events WRE1000 Joos et al, 1999; Plattner et al., 2001

94. How well can ocean carbon cycle model simulate the present state? Selected Results from NCAR CSM1.4-carbon Thanks to S. Doney, I. Fung, K. Lindsay

95. . Observation-based (GLODAP) Anthropogenic CO 2 NCAR CSM1.4 DIC (mol m -2 ) 0 50 100

96. Canth 2100 in Atlantic CSM1.4-carbon Laws et al. (2000) Total: 9.2 Pg C Total: 11.1 Pg C Figure2: Depth vs. latitude contour plot of annual mean anthropogenic CO 2 in the Atlantic Ocean for 2090-2100 simulated with the CSM1.4-carbon.

97. . Ocean Acidification and Aragonite Saturation Observation- based NCAR CSM1.4 supersaturation AA 2 1 4 3 0 AA 2 1 4 3 0

98. . Observation-based Aragonite Saturation in the Atlantic NCAR CSM1.4 supersaturation 0 10 20 -10  CO 3 — [mol/m 3 ] 1000 4000 0 depth [m] 90 o S90 o N

99. . Aragonite Saturation in the Pacific 0 Observation-based 1000 4000 depth [m] NCAR CSM1.4 supersaturation 0 10 20 -10  CO 3 — [mol/m 3 ] 0

100. GLODAP/WOA01 CSM-1.4-carbon Comparison with observations Saturation state Ω A at surface

101. Δ[CO 3 2- ] (umol/cm 3 ) Atlantic Pacific GLODAP/WOA01 CSM-1.4-carbon Comparison with observations

102. Phospate: Model versus Observations CSM1.4-carbonWorld Ocean Atlas (2001) Atlantic 20° W Pacific 167° W

103. Export Production of POC Laws et al. (2000) Global: 9.2 Pg C 0 100 200 Export (g-C m -2 ) CSM1.4 11.1 Pg C 0 100 200

104. Export Production of POC CSM1.4-carbon Laws et al. (2000) Total: 9.2 Pg C Total: 11.1 Pg C Figure2: Depth vs. latitude contour plot of annual mean anthropogenic CO 2 in the Atlantic Ocean for 2090-2100 simulated with the CSM1.4-carbon.

105. AOU Model vs WOA

106. . Apparent Oxygen Utilisation in the Pacific Observation-based NCAR CSM1.4 0 AOU (  mol/kg) 300 200 100 depth 90 o N90 o S

107. . Apparent Oxygen Utilisation in the Atlantic Observation-based NCAR CSM1.4 100 200 300 0 AOU [  mol/kg]

108. . Apparent Oxygen Utilisation in the Indian Observation-based NCAR CSM1.4 100 200 300 0 AOU [  mol/kg]

109. . NCAR CSM1.4 Surface Temperature and CO 2 for SRES A2 and B1 190020002100 Year 300 500 700 CO 2 (ppm) 0 1 2  T ( o C) A2 B1 A2 B1 Anthropogenic forcing - Fossil and land use CO 2 emissions - CH 4, N 2 O, CFCs - direct sulphate aerosols Natural forcing - solar irradiance - stratospheric volcanic aerosols 190020002100 Year Instrumental

110. . NCAR CSM1.4 Decrease in the volume of water oversaturated with respect to aragonite (SRES A2)

111. Difference 2100 - 1820 Decrease in Export of DOM 1820 -2100 ∆ ~ 8 % 18202100 Year

112. Variability and a decreasing trend in meridional overturning circulation 80 o N Latitude 40 o N 0o0o 40 o S 182020002100 Year -10 0 10 20 30 Overturning (Sv) 1900

113. Ocean Acidification: large decrease in the aragonite saturation in the tropics and subtropics Change in saturation state Ω A Difference 2100 – 2000 -200% -100% 0%

114. Ocean Acidification: large changes in the subtropics Saturation state Ω A at surface Difference 2100 – 2000 Evolution 1820-2100 (global zonal mean) Contour lines: Δ[CO 3 2- ] (umol/cm 3 ) 0 2 4 -2 0

115. Difference 2100-1820Hovmoeller Meridional Overturning Circulation Decrease in North Atlantic Ocean

116. Long-term CO 2 and sea level committment in EMICs 1820 -2100 200025003000 200025003000 Year 60% 0 Atmosphere Ocean Land 2000 GtC Thermal Expansion (m) 1 IPCC AR4 EMIC Intercomparison Plattner et al., 2006; Cumulative Emissions 0%

117. 1. Inverse methods such as Ensemble Kalman filtering provide powerful tools for improved estimates of biogeochemical quantities. It is time to include CARBOOCEAN measurements. 2. Bomb radiocarbon data suggest that the OCMIP air-sea transfer velocity field must be downscaled by ~26%; global mean: 16 cm/hr (Müller et al., 2006, Sweeney, 2006, Ho et al., 2006, Nägler et al., 2006) It is time to use a downscaled transfer velocity 3. Simulations with forced and internal variability available It is time to analyse internal and externally-forced variability Conclusions

118. CSM1.4-carbon Fossil only Sabine et al. (2003) CO 2 [mol/m 2 ] Column Inventory of anth. CO 2 1994

119. A Historical Perspective Siegenthaler and Oeschger, Science, 1978: “With climate models becoming more and more realistic, a maximum permissible atmospheric CO 2 level might be found which should not be exceeded if the atmospheric radiation balance is not to be disturbed in a dangerous way. … This scenario clearly does not allow us to go on burning fossil fuel at the present growth rate for a long time … Around the turn of the century new technologies would have to take over a substantial part of global energy production.”

120. (IPCC, 2007, Fig. TS-31) Both past and future anthropogenic carbon dioxide emissions will continue to contribute to warming and sea level rise for more than a millennium, due to the timescales required for removal of this gas from the atmosphere.

121. Atmospheric Increase and Fossil Emissions IPCC, Chap 7, 2007

122. Fraction of Fossil Emissions Staying Airborne IPCC, Chap 7, 2007

123. Evaluating the overall impact in a probabilistic way SRES B1 Knutti et al, 2003 Higher CO 2 under global warming leads to an increased probability for high warming