1. Synthesis of Arctic System Carbon Cycle Research Through Model-Data Fusion Studies Using Atmospheric Inversion and Process-Based Approaches (SASS PI Meeting – 2-4 October 2007) A. David McGuire (Project Leader) USGS - Institute of Arctic Biology - University of Alaska Fairbanks

2. Project Participants McGuire, Hayes, Balshi - UAF Melillo, Kicklighter, Peterson - MBL McClelland, Townsend-Small – U. Texas Follows, Prinn, Manizza, Tan, Li - MIT Zhuang, Hu, Tang - Purdue

3. General Questions Guiding Research 1. What are the geographic patterns of fluxes of CO 2 and CH 4 over the Pan-Arctic region and how is the balance changing over time? (Spatial Patterns and Temporal Variability) 2. What processes control the sources and sinks of CO 2 and CH 4 over the Pan-Arctic region and how do the controls change with time? (Processes and Interactions)

4. Land Atmosphere CO 2 CH 4 Arctic Ocean DOC, DIC, POC Permafrost CO 2 Pacific Ocean Atlantic Ocean Total C Key Fluxes of Carbon in the Arctic System Sea Ice

5. Tasks 1. Conduct model-data fusion studies with process-based models of various components of high latitude terrestrial C dynamics including a. Terrestrial CO 2 (McGuire lead; STM-TEM) and CH 4 exchange (Zhuang lead; MCEM), and b. Transfer of C from high latitude terrestrial ecosystems to the mouth of rivers in the Pan-Arctic Drainage Basin (Melillo/Peterson/McClelland/Kicklighter lead; STM-TEM) 2. Conduct model-data fusion studies with a process-based model of marine CO 2 exchange in oceans adjacent to the high latitude terrestrial regions (Follows lead; ECCO2 and MIT Biogeochemistry Model) 3. Improve atmospheric inversions of CO 2 and CH 4 across high latitude regions through better incorporation of data and process-understanding on CO 2 and CH 4 dynamics (Prinn lead; MATCH Atmospheric Inversion Framework). 4. Project synthesis (All).

6. Time Line of Research First Year – Recruit Project Personnel Second Year – Organize data sets and finish up any necessary model development Third Year – Connect Up the System Fourth Year (no cost extension) – Project Synthesis

7. Progress: The Arctic Carbon Cycle Assessment Sponsored by AMAP, CliC, and IASC Objectives Evaluate the current state of the Arctic carbon cycle. Evaluate potential sensitivities of the Arctic carbon cycle. Evaluate representation of the Arctic C cycle in climate models. Identify the key uncertainties and actions to reduce them. Writing Committee: A. D. McGuire, Leif Anderson, Torben Christensen, Scott Dallimore, Laodong Guo, Dan Hayes, Martin Heimann, Tom Lorenson, Robie MacDonald, and Nigel Roulet Draft: Sensitivity of the Carbon Cycle in the Arctic to Climate Change Workshop Review of Draft – Seattle, February 2007 Submit Assessment by End of 2007

9. Progress: Data Set Organization and Model Development Terrestrial Carbon Dioxide and Methane NHL Fire Data Sets and Analysis – Balshi et al. 2007 (JGR-B) NHL Vulnerability to Fire and Methane – Zhuang et al. 2006 (GRL) Arctic Tundra CO2 and CH4 Assessment – Sitch et al. 2007 (EA) Alaska CO2 and CH4 Assessment – Zhuang et al. 2007 (EA) Snow Cover and CO2 – Euskirchen et al. 2006 (GCB) Western Arctic Linkage Experiment – McGuire et al. in review (EI) NHL Feedbacks to Climate - McGuire et al. 2006 (ARER) NHL Terrestrial Feedbacks – McGuire et al. 2007 (GCTE Book) Land to Ocean Dissolved Organic Carbon DOC Export to the Arctic Ocean - Raymond et al. in press (GBC) Arctic River Simulation: 27 Tg C per yr (TEM) vs. 25 (Raymond) Ocean Simulation of C Fluxes Organization of Simulations (see following slides) Atmospheric Inversion of CO2 and CH4 1996-2001 Methane Exchange – Chen and Prinn 2006 (JGR-A) Improving Data Set of CH4 Retrievals (see following slides)

10. Simulated mean net ecosystem carbon balance: Combination of CO 2, climate, and fire: 1996-2002 (from Balshi et al. 2007) Hayes: Organizing Multiple Disturbance Data Sets g C m -2 yr -1

11. Net Methane Fluxes in the 1990s Net Methane Fluxes = 49 Tg CH 4 yr -1 Emissions = 56 Tg CH 4 yr -1 Consumption = -7 Tg CH 4 yr -1 (Zhuang et al., 2004GBC) New Research Improving Changes in Wetlands (Seasonal to Decadal)

12. 0 1 2 4 8 16 32 315 g C m -2 yr -1 Annual DOC Leaching from Contemporary Ecosystems of Arctic Basins during the 1990s Kicklighter et al. in preparation

13. Tracking Sources of Riverine DOC @ surface

14. Scatter plot of yearly averaged CH 4 column burden by SCIAMACHY vs. MATCH (on each model grid). Slope is 1.01, i.e., good agreement in spatial gradient. Large offsets (~8%), contamination by clouds, aerosols?

15. Opportunities for Linkages to Other Project Greening of the Arctic (Walker) Humans and Hydrology in High Latitudes (Lammers) Synthesis of Arctic Marine Primary Production (Matrai) Impact of Sea Ice on the Marine Production (Zhang) An Arctic Snow-Impacts Synthesis (Sturm)