Integrative Ecosystem Science

When carbon is emitted into the atmosphere, some stays there and contributes to global warming while the rest is taken up by oceans and lands. Scientists at the Climate Change Science Institute at Oak Ridge National Laboratory track carbon’s movement through permafrost, bogs, forests, and other terrestrial ecosystems to understand feedbacks to the climate. They employ information from large-scale field studies, global databases, and community models in simulations of, for example, how droughts and wildfires affect carbon cycling or how much carbon dioxide deciduous trees can remove from the atmosphere and how much of that greenhouse gas soil microbes can release. The Integrative Ecosystem Science (IES) group’s primary objective is to improve the ability to make future climate projections with a coupled Earth system model like the Community Earth System Model. The scientists have identified numerous areas where feedbacks happen between land ecosystems—especially the carbon and nutrient biogeochemistry of those ecosystems—and the climate system as a whole.

Photosynthesis largely governs the uptake of atmospheric carbon dioxide on land. How much atmospheric carbon dioxide land can absorb depends on the availability of growth-limiting resources, such as phosphorus in rainforests or light in the Arctic during winter. How long the carbon stays out of the atmosphere depends on whether it has been assimilated into long-term reservoirs such as wood or short-term sinks such as leaves. Human activities, from farming and urban sprawl to burning fossil fuels and forests, are the biggest drivers of long-term changes in carbon storage in terrestrial ecosystems. Because models are the means for simulating climate a century from now, the CCSI scientists strive to make sure modeled processes accurately represent the natural world. 

Through the Integrative Ecosystem Science Focus Area and other projects, CCSI scientists leverage strengths in observation, experiment, modeling, and computation. Notably, the Climate Science for a Sustainable Energy Future project pioneers this integrated approach. Its partners at Oak Ridge, Argonne, Brookhaven, Lawrence Berkeley, Lawrence Livermore, Pacific Northwest, and Sandia national laboratories and the National Center for Atmospheric Research aim to accelerate the development of the Community Earth System Model’s sixth version, scheduled to be released for predictive simulation in 5 to 10 years. The TECCS group quantifies uncertainties with interactions between carbon and nutrient cycles in land.

Another CCSI undertaking is the Integrated Earth System Modeling project, the first effort to couple an integrated assessment model (the Global Change Assessment Model, representing human activities affecting land use and greenhouse gas emissions, from Pacific Northwest National Laboratory), to a fully dynamic Earth system model, CESM, which links independent models of atmosphere, ocean, land, and ice. The CESM teams include groups at ORNL and at Lawrence Berkeley National Laboratory, working with the Community Land Model, the full CESM model, and new coupling software. Improved modeling of feedbacks of terrestrial ecosystems to climate will empower explorations of energy systems, hydrology, and climate adaptation and mitigation options.