Hill Heat

Program Summary How Fast is Atmospheric CO2 Growing and Why, and Does it Suggest Ways to Mitigate Climate Change?

The increase in atmospheric carbon dioxide (CO2) is the single largest human perturbation of the climate system. Its rate of change reflects the balance between human-driven carbon emissions and the dynamics of a number of terrestrial and ocean processes that remove or emit CO2. It is the long term evolution of this balance that will determine to a large extent the speed and magnitude of climate change and the mitigation requirements to stabilize atmospheric CO2 concentrations at any given level. Dr. Canadell will present the most recent trends in global carbon sources and sinks, updated for the first time to the year 2007, with particularly focus on major shifts occurring since 2000. Dr. Canadell’s research indicates that the underlying drivers of changes in atmospheric CO2 growth include: i) increased human-induced carbon emissions, ii) stagnation of the carbon intensity of the global economy, and iii) decreased efficiency of natural carbon sinks. New Estimates of Carbon Storage in Arctic Soils and Implications in a Changing Environment

The Arctic represents approximately 13% of the total land area of the Earth, and arctic tundra occupies roughly 5 million square kilometers. Arctic tundra soils represent a major storage pool for dead organic carbon, largely due to cold temperatures and saturated soils in many locations that prevent its decomposition. Prior estimates of carbon stored in tundra soils range from 20-29 kg of soil organic carbon (SOC) per square meter. These estimates however, were based on data collected from only the top 20-40 cm of soil, and were sometimes extrapolated to 100 cm. It is our understanding that large quantities of SOC are stored at greater depths, through the annual freezing and thawing motion of the soils (cryoturbation), and potentially frozen in the permafrost.

Recent detailed analysis of Arctic soils by Dr. Epstein and his colleagues found that soil organic carbon values averaged 34.8 kg per square meter, representing an increase of approximately 40% over the prior estimates. Additionally, 38% of the total soil organic carbon was found in the permafrost.

A total of 98.2 gigatonnes (1015 grams) of carbon is estimated to be stored in the soils of the North American Arctic tundra. An area-based estimate for the entire Arctic suggests the presence of approximately 160 gigatonnes of carbon. The annual increase in atmospheric carbon dioxide is roughly 2% of this amount, so small changes in Arctic carbon storage could have substantive impacts on atmospheric CO2. The future of this stored carbon is, however, largely uncertain in the face of a changing Arctic environment. Climate change and resulting increasing temperatures in much of the Arctic could increase the decomposition rates of soil organic carbon (producing atmospheric CO2), and increase permafrost thaw, which would expose more soil organic carbon for decomposition. On the other hand, increasing temperatures could also lead to greater sequestration of atmospheric CO2 by tundra vegetation. Actual changes will be the result of complex interactions between processes that sequester carbon and those that release it. Past, Present and Future Changes in Permafrost and Implications for a Changing Carbon Budget

Presence of permafrost is one of the major factors that turn northern ecosystems into an efficient natural carbon sink. Moreover, a significant amount of carbon is sequestered in the upper several meters to several tens of meters of permafrost. Because of that, the appearance and disappearance of permafrost within the northern landscapes have a direct impact on the efficiency of northern ecosystems to sequester carbon in soil, both near the ground surface and in deeper soil layers. Recent changes in permafrost may potentially transform the northern ecosystems from an effective carbon sink to a significant source of carbon for the Earth’s atmosphere. Additional emissions of carbon from thawing permafrost may be in the form of CO2 or methane depending upon specific local conditions.

Dr. Romanovsky will present information on changes in terrestrial and subsea permafrost in the past during the last glacial-interglacial cycle and on the most recent trends in permafrost in the Northern Hemisphere. He will further discuss the potential impact of these changes in permafrost (including a short discussion on potential changes in methane gas clathrates) on the global carbon cycle. Dr. Romanovsky’s research suggests that permafrost in North America and Northern Eurasia shows a substantial warming during the last 20 to 30 years. The magnitude of warming varied with location, but was typically from 0.5 to 2°C at 15 meters depth. Thawing of the Little Ice Age permafrost is on-going at many locations. There are some indications that the late-Holocene permafrost started to thaw at some specific undisturbed locations in the European Northeast, in the Northwest and East Siberia, and in Alaska. Future projections of possible changes in permafrost during the current century, based on the application of calibrated permafrost models, will be also presented. Biographies

Dr. Josep (Pep) Canadell is the executive director of the Global Carbon Project (GCP) based at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia. His work involves internationally coordinated research on i) global and regional carbon budgets and trends, ii) vulnerable carbon reservoirs to changes in climate and land use, and iii) climate mitigation strategies to stabilize atmospheric carbon dioxide. He has published over 70 scientific papers, 8 books and special issues, and the first global environmental change encyclopedia.

Dr. Canadell received his MSc. and Ph.D. degrees on terrestrial ecology from the University Autonomous of Barcelona, Spain, and took several research positions during the 1990s at the University of California at San Diego and Berkeley, and at Stanford University, CA.

Dr. Howard Epstein is an Associate Professor in the Department of Environmental Sciences at the University of Virginia, specializing in the ecology of arctic tundra, and dry grasslands and shrublands. His current research projects in the Arctic involve 1) the study of land-surface features in arctic tundra related to freezing and thawing of soils, 2) the “greening” of arctic tundra vegetation in response to recent warming, and 3) patterns of arctic tundra vegetation and soils along latitudinal temperature gradients in the Arctic of North America and Russia. Studies outside of the tundra include 1) wind erosion effects on plant community changes in the deserts of southeastern New Mexico, 2) carbon and water cycling in a subalpine ecosystem of western Montana, and 3) carbon sequestration during vegetation recovery in abandoned crop fields of northern Virginia.

Dr. Epstein received an M.S. degree in Rangeland Ecosystem Science from Colorado State University in 1995 and a Ph.D. in Ecology, also from Colorado State, in 1997. He later engaged in postdoctoral studies at the Institute of Arctic and Alpine Research at the University of Colorado. Dr. Epstein came to the faculty of the University of Virginia in 1998. As part of his arctic research, he has traveled north of the Arctic Circle nearly every summer since 1999 and recently returned from a field expedition in northwestern Siberia. He teaches courses in the Fundamentals of Ecology, Terrestrial Ecology, and Ecology of Grasslands and Tundra. He has published approximately 60 peer-reviewed journal articles and book chapters on Arctic tundra and dryland ecology.

Dr. Vladimir Romanovsky is a Professor in Geophysics at the Geophysical Institute and the Department of Geology and Geophysics, University of Alaska Fairbanks. He also heads the Geophysical Institute Permafrost Laboratory (www.gi.alaska.edu/snowice/Permafrost-lab). His work involves internationally coordinated research on permafrost temperature changes in Alaska, Russia, Canada, Greenland, Kazakhstan, and Mongolia. He is also involved in numerical modeling of past, present and future permafrost dynamics and the remote sensing of permafrost and related cold-climate processes. Dr. Romanovsky’s research interests include the scientific and practical aspects of environmental and engineering problems involving ice and permafrost. These include problems in the areas of soil physics, thermodynamics, heat and mass flow, and growth and decay processes that are associated with permafrost, subsea permafrost, seasonally frozen ground, and seasonal snow cover. Dr. Romanovsky is the author of 110+ peer reviewed scientific journal publications, reports, and book chapters. He was a co-author of the 2005 Arctic Climate Impact Assessment for Chapter 6 “Cryosphere and Hydrology” and the lead author of Chapter 7 “Frozen Ground” in UNEP’s 2007 Global Outlook for Ice and Snow.

Dr. Romanovsky received his MSc. in Geophysics, MSc. in Mathematics and a Ph.D. in Geology from the Moscow State University in Russia. He also received a Ph.D. in Geophysics from the University of Alaska, Fairbanks. He has held several research and teaching positions at the Moscow State University prior to moving to Alaska in 1992, where he is currently a professor at the University of Alaska, Fairbanks.