Towards Quantitative Evaluation of Ocean Tracer Model

Simulations

J. C. Orr 1, K. G. Caldeira 2, K. E. Taylor 3

and the OCMIP Group*

1LSCE/CEA/CNRS and IPSL (France)2LLNL3PCMDI / LLNL

34th International Liège ColloquiumTracer Methods in Geophysical Fluid Dynamics

6 May 2002

http://www.ipsl.jussieu.fr/OCMIP

OCMIP-2 Group• AWI (Bremerhaven, Germany): R. Schlitzer, M.-F. Weirig • CSIRO (Hobart, Australia): R. Matear• IGCR/CCSR (Tokyo, Japan): Y. Yamanaka, A. Ishida• IPSL (LSCE, LODyC, Paris, France): J. Orr, P. Monfray, O. Aumont, J.-Cl.Dutay,

P. Brockmann • LLNL (Livermore, CA, USA): K. Caldeira, M. Wickett• MIT (Boston, USA): M. Follows, J. Marshall• MPIM (Max Planck Institut fuer Meteorologie – Hamburg, Germany): E. Maier-Reimer • NCAR (Boulder, CO, USA): S. Doney, K. Lindsay, M. Hecht • NERSC (Bergen, Norway): H. Drange, Y. Gao• PIUB (Bern, Switzerland): F. Joos, K. Plattner • PRINCEton (Princeton, USA): J. Sarmiento, A. Gnanadesikan, R. Slater, R. Key• SOC (Southampton Oceanography Centre/ Hadley Center, UK): I. Totterdell, A. Yool • UL (University of Liege/University Catholique de Louvain, Belgium):

A. Mouchet, E. Deleersnijder, J.-M. Campin• PMEL/NOAA (Seattle, USA): J. Bullister, C. Sabine• PSU (Penn. State, USA): R. Najjar, F. Louanchi• UCLA (Los Angeles, USA): N. Gruber, X. Jin

The OCMIP-2 models differ

Resolution

Seasonality

Boundaryconditions

Sub-grid mixing

Mixed Layer

Sea-ice Model

Offline/Online

How Good is a Model?

• Relative to data• Relative to other models• Skill assessment depends on

– Our Objectives (e.g., mean state vs. variability)

– Our Vision• Rose colored glasses• Dark Sunglasses• Clear glasses?

– Local, Qualitative Analysis

– Global, Quantitative Analysis

• Tracers– CFC-11 and CFC-12– Natural C-14 and Bomb C-14– He-3 and He-4

• Carbon– Preindustrial:

• Abiotic• Common Biogeochemistry (∑CO2, Alk, PO4, O2, DOM)

– Preindustrial to Present– Future (two IPCC scenarios: IS92a, S650)– Sequestration (7 sites, 3 depths, 2 scenarios)

OCMIP-2 Simulations

3-

Global OceanAnnual Mean Sea-Air CO2 Flux in 1995 (mol m-2 yr-1)

Some Summary Statistics

• Standard deviations – reference – model

• Correlation Coefficient R:

• Centered Pattern RMS error:

• Overall Bias:

Law of Cosines:

*Taylor, K.E., J. Geophys. Res., 106, D7, 7183-7192, 2001

Key relationship:

A Useful Diagram*

Taylor Plot: Sea-Air CO2 Flux (1995 Annual Mean, Global Map)

Taylor Plot: Sea-Air CO2 Flux (1995 Full Global Space-Time Distribution)

Basin Zonal IntegralsAnnual Mean Sea-Air CO2 Flux in 1995 (Pg C yr-1 deg-1)

GlobalSeasonalZonal Integral Sea-Air CO2 Flux in 1995 (Pg C yr-1 deg-1)

Sea-Air CO2 Flux: Pacific Ocean

North Pacific: 22oN-70oN Equatorial Pacific: 22oS-22oN

Conclusions: Total CO2 validation

• Taylor* Diagram: graphical evaluation of 5 global summary statistics (σdata, σmodel, r, R.M.S., Bias)

– Provides quick, global roadmap

– Motivates further evaluation

– Not mechanistic

• Air-sea CO2 flux– OCMIP-2 models succeed in terms of zonal mean

– OCMIP-2 models fail in terms of zonal and seasonal anomalies

*Taylor, K. E., J. Geophys. Res., 106, D7, 7183-7192, 2001

Taylor Plot for Deep 14C (below 1000 m)

Natural 14C(West Atlantic,GEOSECS Section)

Some models over-predict 14C

Some models under-predict 14C

Pacific OceanWOCE P16 14C

Some models under-predict 14C

Some models over-predict 14C

Data

CFC-11 in the South Atlantic

Dutay et al., Ocean Modell., 2001

Ajax Data

Some models under-predict CFC uptake

Some models over-predict CFC uptake

Anthropogenic CO2 uptake is correlated with CFC-11 uptake and ∆14C

Global CFC-11 Inventory (1989) Mean ∆14C below 1000 m

Data-basedestimate

Simulated 1995anthropogenic CO2 columninventories

Some models take up little CO2 in the Southern Ocean

Some models take up a lot of CO2 in the Southern Ocean

Sabine et al., 2001

Global air-sea anthropogenic CO2 flux (Pg C yr-1)

Summary of OCMIP2 anthropogenic CO2 simulations

• Some agreement on global historical CO2 uptake by the ocean– For the 1980’s = 2.0 ± 0.4 PgC yr–1

– For the 1990’s – IS92a = 2.5 PgC yr–1

– adjusted IS92a = 2.2 PgC yr–1

• Some disagreement on regional and future fluxes– 1980’s and 1990’s +/-13% (about the mean) – Year 2100 +/-20% (IS92a and S650)– Year 2300 +/-35% (S650)

Rationale for CO2 uptake estimate

• Observed natural ∆14C values are within the range of model results.• Modeled CO2 uptake is correlated with modeled ∆14C

• Observed CFC-11 concentrations are within the range of model results

• Modeled CO2 uptake is correlated with modeled [CFC-11]

• Independently estimated anthropogenic CO2 inventories are within the range of model results

• Therefore, anthropogenic CO2 uptake by the real ocean is probably within the range of model results.

• Ocean CO2 uptake for the 1980’s = 2.0 ± 0.4 PgC yr–1

– IS92a 1990’s = 2.5 PgC yr–1

– Adjusted IS92a 1990’s = 2.2 PgC yr–1

Back-up slides

Efficiency of deep CO2 injection is also correlated with CFC-11 uptake

and ∆14C Global CFC-11 Inventory (1989)

Mean ∆14C below 1000 m

Global Sea-Air CO2 Flux in 1995 (Zonal Integral, Annual Mean, Pg C yr-1

deg-1)

Pacific Sea-Air CO2 Flux in 1995 (Zonal Integral, Annual Mean, Pg C yr-1

deg-1)

Anthropogenic CO2 vs. CFC-11

Gruber et al., 2001

Simulated 1995 cumulativeCO2 fluxes and inventory

Large model differences in the Southern Ocean

US Groups are anticipating funding

• Inverse basis function simulations– Gruber et al.

• Automated Model Ocean Diagnosis (AutoMOD), companion to NOCES, focusing on NASA data products– Caldeira et al.

Next steps

• Special OCMIP2 section in Global Biogeochemical Cycles

• IGBP open workshop “Global issues in ocean biogeochemistry” – May or June 2002– GAIM, CLIVAR, JGOFS, GLOBEC, LOICZ, SOLAS

• EurOCMIP3 project (NOCES)– Emphasis on interannual to interdecadal variability– A wide range of model types (5 global ocean models, 1 regional

ocean model, 1 inverse atmospheric inverse model)

• US proposals expecting funding– Inverse basis function simulations (Niki Gruber)– Automated Model Ocean Diagnosis (Ken Caldeira)

Global Biogeochemical CyclesOCMIP2 Special Section

• An overiew and history of OCMIP – J. Orr and N. Gruber

• Comparison of model physics relevant to the carbon Cycle in OCMIP2– K. Lindsay (NCAR)

• OCMIP2 evaluation of deep-ocean circulation deduced from 3He and 4He simulations– J. Dutay (LSCE)

• Efficiency of purposeful CO2 injection in the deep ocean: comparison of the OCMIP2 models

– J. Orr (LSCE)

• Air-sea fluxes and north-south ocean transport of CO2 and O2: results from OCMIP2– P. Monfray (LSCE)

• Comparison of new and export production from the OCMIP2 models– R. Najjar (Penn State)

• Simulations of historical and future anthropogenic CO2 uptake from OCMIP2 models– J. Orr (LSCE)

• Comparisons of model- and data-based estimates of anthropogenic CO2 in the oceans

– C. Sabine (PMEL)

Proposed IGBP open workshop

• TITLE: Global Scale Issues in Ocean Biogeochemistry• WHERE: Ispra in Italy, (host N.Hoepffner at JRC)• WHEN: May or June 2002• DURATION: 4 days at least (to give time for plenary discussion)• SIZE: 60 (?) with 20 invited• CO-ORGANIZERS: R.Schlitzer & P.Monfray ?• PURPOSES :

– Address big questions in global scale ocean biogeochemistry based on recent data, process modeling, and synthesis

– Bridge the gaps between physics, biogeochemistry, and biology– Bridge the gap between people working on observations, process

modeling, and global modeling– Stimulate strong concerted action in global scale research

• TARGET COMMUNITIES: – CLIVAR, JGOFS, GLOBEC, LOICZ and SOLAS