Synthesis & Modeling Project
Nicolas Gruber

Chris L. Sabine
R. Sonnerup
John Bullister
Robert M. Key

Global Assessment and Synthesis of Data Based Estimates of Anthropogenic CO2 in the Ocean


PROJECT DESCRIPTION: The ocean is second only to the atmosphere as a sink for anthropogenic CO2. Over the last decade, our ability to quantify the oceanic sink using observations has dramatically increased. The improvement derives from two major factors. The first was the JGOFS/WOCE/OACES global ocean carbon survey, which produced the first global scale high-quality inorganic carbon data set. Second is the continuing development of improved techniques to estimate anthropogenic carbon from the new measurements. Regardless, significant uncertainties remain regarding estimation of the spatial distribution of anthropogenic CO2 uptake and storage. This uncertainty comes from the fact that separation of the natural and anthropogenic CO2 signals is far from trivial. The estimates require assumptions that are difficult to verify and whose uncertainties are hard to estimate. Better quantification of the spatial storage pattern and its uncertainty are required to assess the value of oceanic data constraints on global carbon budget analyses and ocean model evaluations, such as undertaken by the Ocean Carbon-cycle Model Intercomparison Project (OCMIP). 

We propose to carry out a global analysis of observation-based estimates of the oceanic storage of anthropogenic CO2. The goal is to assess a range of ocean data based approaches to provide a well constrained estimate of the oceanic anthropogenic CO2 distribution. Particular emphasis will be put on uncertainty estimation and differences between the various approaches. The work proposed here depends upon and extends results from recently completed and ongoing JGOFS SMP research, however there is no duplication. The effort will be carried out under the Global Ocean Data Analysis Project (GLODAP) organizational umbrella. 

Our research will focus on two areas. First, we will attempt to improve the direct anthropogenic CO2 inventory estimates using observations in conjunction with model simulation results from OCMIP. Specifically, we will critically examine the DeltaC* methodology of Gruber et al. (1996) and MIX methodology of Goyet et al. (1999). Second we will explore how isotopic and non-carbon transient tracer data (i.e. bomb C14, delta C13, CFCs, and CCl4) can be used to evaluate anthropogenic CO2 estimates or even provide alternative estimation methods. The robustness of these approaches will be investigated using the OCMIP model results. Finally, we will synthesize the results to provide better estimates of the distribution and uncertainty of anthropogenic CO2 in the ocean and provide suggestions for improved approaches for the future. 

We have gathered a team that has expertise in the analysis and interpretation of a wide range of oceanic tracers, consisting of Nicolas Gruber (UCLA) as PI, Christopher L. Sabine (UW), Rolf Sonnerup (UW), John Bullister (NOAA PMEL) and Robert M. Key (Princeton) as Co-PIs. We will collaborate with Jorge Sarmiento (Princeton) who was recently funded to improve the Princeton ocean circulation model and to perform sensitivity experiments with regard to transient tracer uptake. We believe that the coordinated examination of a suite of transient tracers and methodologies that historically have been examined independently promises a much improved understanding of the ocean's role in the global carbon cycle. It will also provide a robust benchmark for ocean carbon cycle models used to predict future oceanic CO2 uptake. 

DATA: - no data products generated -
PUBLICATIONS: Sabine, Christopher L., et al. 2004. The Oceanic Sink for Anthropogenic CO2. Science 305: 367-371. ( .5 Mb PDF )

RELATED PROJECTS: Gruber "Analyzing and modeling interannual to decadal variability in the carbon cycle of the subtropical and subpolar gyres."

Key; Gordon; Sabine; Gruber; Mordy "Determination of the Redfield remineralization ratios based on neutral surface analysis of the new global data set"

Sabine; Key; Feely; Bullister; Millero; Wanninkhof; Peng; Kozyr "Synthesis and interpretation of the NOAA/DOE global CO2 survey data"

Nicolas Gruber
Inst. Geophysics and Planetary Physics & Dept of Atmospheric Sciences
University of California, Los Angeles
5853 Slichter Hall
Los Angeles, CA 90095-1567
tel: 310-825-4772
fax: 310-206-3051

Christopher Sabine
7600 Sandpoint Way NE 
Seattle, WA 98115 
tel: (206) 526-4809 
fax: (206) 526-6744 

Rolf Sonnerup
7600 Sandpoint Way NE 
Seattle, WA 98115 
tel: (206) 526-6748

John L. Bullister
7600 Sand Point Way NE 
Seattle, WA 98115 
tel : (206) 526-6741 

Robert M. Key
Program in Atmospheric and Ocean Sciences 
Department of Geosciences, Guyot Hall 
Princeton University 
Princeton, NJ 08544-1003 
tel: (609) 258-3595 
fax: (609) 258-1274