Focus Areas

Climate Change Forcing

1.1 Carbon Cycle

Scientific Imperative.
The goal of Berkeley Lab’s Terrestrial Carbon research is to support the development, testing, and application of Integrated Terrestrial Carbon Models (ITCMs) that will be used to simulate carbon fluxes in North America in the near term, and coupled with global climate models in the long term. This work is a multi-institution collaboration under the coordination of the lead lab in this SFA, Oak Ridge. Berkeley Lab is pursuing five areas of research relevant to improving carbon cycle understanding: (1) better characterization of ecosystem CO2 fluxes and resulting atmospheric concentrations; (2) spatally and temporally resolved measurements of fossil CO2 emissions; (3) better understanding of soil carbon cycling; (4) simulation of feedbacks between carbon dynamics and climate change in global carbon-climate models; and (5) diagnosis of carbon modules in global climate models using AmeriFlux, North American Carbon Program (NACP), and other carbon system observations.

There is a pressing need for data with which to challenge the ITCM and global carbon-climate models, as well as data for the interagency North American Carbon Program. This need has made  regional and continental CO2 budgets a priority, as is elucidating the mechanisms, forcings, and resolution required to accurately simulate these budgets. Model testing is necessary not only for carbon cycle components, but also for submodels of radiation (which drives, for example, photosynthesis) and other surface trace gas fluxes (e.g., CH4). For example, precise atmospheric CO2 can improve atmospheric estimates. ECMWF has concluded that CO2 concentration uncertainty contributes up to 1ºC uncertainty in atmospheric temperature estimates. See Section 4 for the scientific imperative regarding soil carbon cycling.

Core capabilities.
Berkeley Lab is addressing data needs and contributing to ecosystem and atmospheric modeling, through work supported by the  Atmospheric Radiation Measurement (ARM) and Terrestrial Carbon Processes (TCP) programs, on atmospheric measurements (ARM), fossil fuel CO2 emissions (TCP), and soil carbon cycling (TCP).

First, with ARM support, Berkeley Lab has designed and implemented a coordinated suite of carbon concentration, isotope, and flux measurements in the Southern Great Plains. With simultaneous monitoring from crop fields, tall tower, and aircraft, this facility is possibly the best-instrumented site for regional carbon studies in the world. Moreover, all the data are processed with consistent formats, well documented, and provided to the ARM public access archives. The data are being used by modelers in the U.S. and internationally. As a result, the ARM/Berkeley Lab Carbon Project is developing an increasingly prominent profile in U.S. carbon cycle science.

In addition to making large-scale carbon observations in the Great Plains and Western U.S., Berkeley Lab has an accomplished modeling team. We have developed and tested high-resolution coupled atmosphere-land-surface models for ecosystem greenhouse gas fluxes, including isotopic tracers.  We have also spearheaded the application of AmeriFlux and other observations to assess the performance of terrestrial carbon models coupled to the DOE-NCAR Community Climate System Model (CCSM). These efforts directly support NACP as well as other regional and global modeling efforts.

Moreover, Lab investigators will develop new, detailed regional models of biogeochemical fluxes for application within the Terrestrial Carbon Processes Program.

Second, with TCP support, Berkeley Lab (PI Fischer) is collaborating with Kevin Gurney (Purdue University) to develop maps of fossil-fuel-derived CO2 with sufficient spatial and temporal resolution for use in atmospheric inverse model estimates of regional biosphere exchange. This work is essential for NACP, because many regions of the continental U.S. have strong and spatially variable fossil CO2 emissions, which are not adequately characterized at the regional scale. We have propagated our emissions map through the atmosphere using a mesoscale transport model and compared the results with measured radiocarbon in grassland vegetation across California. The high correlation between measured and simulated fossil CO2 concentrations demonstrated that the method could be applied to larger spatial scales. We expect to complete a fully functional, high-resolution representation of U.S. fossil CO2 emissions in FY08. After validation against DOE–EIA data, maps will be released for use in NACP activities.

Finally, Berkeley Lab has active research in belowground carbon cycling. In direct response to BER priorities, our work will contribute to integrated terrestrial carbon models, state-of-the-carbon-cycle assessments, and climate change feedback predictions via TCP-funded projects (PI Torn).  Although integration with BER TCP is described in this section, for brevity, the bulk of our soil carbon research (including scientific imperative, competencies, specific projects, and milestones) is described in Section 4, Terrestrial Carbon Sequestration.

Scientific Milestones.
Our research goals in Carbon and Ecosystem Climate Forcing for the next five years include:

1. Lead NACP intensives in the Southern Great Plains, through CLASIC and ongoing measurements. We will provide data for an intercomparison of approaches for estimating regional scale C and energy fluxes.
2. Create data products of atmospheric trace gas concentrations and ecosystem fluxes for testing and assimilation of land surface and coupled climate-carbon cycle models. We are creating metrics to determine necessary spatial and temporal resolution required to capture heterogeneity in ecosystem-atmosphere C and energy fluxes.
3. Complete development of high-resolution fossil fuel CO2 emissions maps for atmospheric inverse model estimates of regional biospheric CO2 exchange. Conduct map validation exercises against independent county level inventory estimates of CO2 emissions in collaboration with the California Air Resources Board. Continue radiocarbon comparison exercises in collaboration with Ameriflux and NACP researchers across continental U.S.
4. Develop metrics, using AmeriFlux and other carbon system observations, for assessing the performance of terrestrial carbon models coupled to global climate models
5. Assimilate terrestrial and oceanic carbon observations into global carbon-climate models to improve the representation of carbon dynamics in the models.

Moreover, Berkeley Lab, together with UC Berkeley and the University of Maryland, has been funded by SciDAC to assimilate all carbon system observations (atmospheric CO2 , aircraft, flux towers, satellite, air-sea fluxes) into the DOE-NCAR coupled carbon-climate model. Within the next 3 years, this effort will produce the first global distribution of atmospheric CO2 distribution that is consistent with all available terrestrial and oceanic observations.

Ocean Carbon Cycle:
Berkeley Lab is also carrying out innovative observations in ocean carbon cycle that would contribute to removing a major gap in coupled carbon-climate modeling. The work is in several areas: (1) autonomous high-frequency observations of the profiles of carbon system parameters in the ocean; and (2) high-tech (e.g., ALS, ICPMS) analysis of oceanic particulate matter to yield insight into the chemical and biological composition, and hence into the mechanisms for carbon and nutrient transport in the oceans.
This ocean-carbon work has yielded new information about new sources of iron to support marine productivity, as well as the variation in carbon remineralization length scales (assumed to be globally invariant in climate models) with physical and biological regimes,
The Berkeley Lab ocean work has been supported by BER and is central to improving carbon-climate models for predicting future atmospheric CO2 levels. The Lab envisions continuing work in several areas:

1. Expansion of the suite of carbon system parameters observable by the autonomous carbon explorers beyond biomass and particulate inorganic carbon to include flux of particulate organic and inorganic carbon as well as dissolved organic carbon;
2. Investigation of sources and sinks of bioreactive trace metals important to phytoplankton productivity, carbon sedimentation, and hence ocean uptake of CO2;

development of new parameterizations of ocean carbon processes using the new and unique ocean carbon system observations.