Intercomparison of the Wetchimp-Wsl Wetland Methane Models over West Siberia: How Well Can We Simulate High-Latitude Wetland Methane Emissions?

Thursday, 18 December 2014: 5:45 PM
Theodore J Bohn1, Joe R Melton2, Victor Brovkin3, Guangsheng Chen4, Sergey N. Denisov5, Alexey V Eliseev5,6, Angela V Gallego-Sala7, Mikhail Glagolev8,9, Akihiko Ito10, Jed O. Kaplan11, Thomas Kleinen3, Shamil S Maksyutov12, Kyle C McDonald13,14, Michael A Rawlins15, William J Riley16, Ronny Schroeder17, Renato Spahni18, Benjamin Stocker18, Zachary M Subin19, Hanqin Tian20, Bowen Zhang20, Xudong Zhu21,22 and Qianlai Zhuang21, (1)Arizona State University, Tempe, AZ, United States, (2)CCCma, Victoria, BC, Canada, (3)MPI for Meteorology, Hamburg, Germany, (4)Oak Ridge National Laboratory, Oak Ridge, TN, United States, (5)Russian Academy of Sciences, A. M. Obukhov Institute of Atmospheric Sciences, Moscow, Russia, (6)Kazan Federal University, Kazan, Russia, (7)University of Exeter, Exeter, United Kingdom, (8)Moscow State University, Moscow, Russia, (9)Russian Academy of Sciences, Institute of Forest Science, Uspenskoe, Russia, (10)CGER-NIES, Tsukuba, Japan, (11)University of Geneva, Geneva, Switzerland, (12)NIES National Institute of Environmental Studies, Ibaraki, Japan, (13)CCNY-Earth & Atmos Sciences, New York, NY, United States, (14)Jet Propulsion Laboratory, Pasadena, CA, United States, (15)University of Massachusetts Amherst, Amherst, MA, United States, (16)Lawrence Berkeley Natl Lab, Berkeley, CA, United States, (17)CUNY City College, New York, NY, United States, (18)University of Bern, Bern, Switzerland, (19)Princeton University, Princeton, NJ, United States, (20)Auburn University at Montgomery, Auburn, AL, United States, (21)Purdue University, West Lafayette, IN, United States, (22)Colorado State University, Natural Resource Ecology Laboratory, Fort Collins, CO, United States
Wetlands are the world’s largest natural source of methane, a powerful greenhouse gas. The strong sensitivity of these emissions to environmental factors such as soil temperature and moisture has led to concerns about potential positive feedbacks to climate change. This is particularly true at high latitudes, which have experienced pronounced warming and where thawing permafrost could potentially liberate large amounts of labile carbon over this century. Despite the importance of wetland methane emissions to the global carbon cycle and climate dynamics, global models exhibit little agreement as to the magnitude and spatial distribution of emissions, due to uncertainties in both wetland area and emissions per unit area driven by a scarcity of in situ observations. Recent intensive field campaigns across West Siberia make this an ideal region over which to assess the performance of large-scale process-based wetland models in a high-latitude environment. Here we present the results of a follow-up to the Wetland and Wetland CH4 Model Intercomparison Project focused on the West Siberian Lowland (WETCHIMP-WSL). We assessed 17 models and 5 inversions over this domain in terms of total CH4 emissions, simulated wetland areas, and CH4 fluxes per unit wetland area and compared these results to an intensive in situ CH4 flux dataset, several wetland maps, and two satellite inundation products. Findings include: a) estimates of total CH4 emissions from both models and inversions spanned almost an order of magnitude; b) forward models using inundation alone to estimate wetland areas suffered from severe biases in CH4 emissions; and c) aside from these area-driven biases, disagreement in flux per unit wetland area was the main driver of forward model uncertainty. We examine which forward model approaches are best suited towards simulating high-latitude wetlands and make recommendations for future modeling, remote sensing, and field campaigns to reduce model uncertainty.