Old Rocks
Diamond Member
Permafrost carbon-climate feedbacks accelerate global warming
Permafrost carbon-climate feedbacks accelerate global warming
Charles D. Kovena,b,1, Bruno Ringevala, Pierre Friedlingsteinc, Philippe Ciaisa, Patricia Cadulea, Dmitry Khvorostyanovd, Gerhard Krinnere, and Charles Tarnocaif
+ Author Affiliations
aLaboratoire des Sciences du Climat et de lEnvironnement, Centre National de la Recherche Scientifique/Commissariat à lEnergie Atomique, 91191 Gif-sur-Yvette, France;
bEarth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;
cCollege of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, United Kingdom;
dLaboratoire de Météorologie Dynamique, École Polytechnique, 91128 Palaiseau, France;
eLaboratoire de Glaciologie et Géophysique de lEnvironnement, Centre National de la Recherche Scientifique/Université Joseph Fourier, Grenoble 1, Unité Mixte de Recherche 5183, F-38402 Grenoble, France; and
fAgriculture and Agri-Foods Canada, Ottawa, ON, Canada K1A 0C5
Edited* by Inez Y. Fung, University of California, Berkeley, CA, and approved July 12, 2011 (received for review March 24, 2011)
Abstract
Permafrost soils contain enormous amounts of organic carbon, which could act as a positive feedback to global climate change due to enhanced respiration rates with warming. We have used a terrestrial ecosystem model that includes permafrost carbon dynamics, inhibition of respiration in frozen soil layers, vertical mixing of soil carbon from surface to permafrost layers, and CH4 emissions from flooded areas, and which better matches new circumpolar inventories of soil carbon stocks, to explore the potential for carbon-climate feedbacks at high latitudes. Contrary to model results for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4), when permafrost processes are included, terrestrial ecosystems north of 60°N could shift from being a sink to a source of CO2 by the end of the 21st century when forced by a Special Report on Emissions Scenarios (SRES) A2 climate change scenario. Between 1860 and 2100, the model response to combined CO2 fertilization and climate change changes from a sink of 68 Pg to a 27 + -7 Pg sink to 4 + -18 Pg source, depending on the processes and parameter values used. The integrated change in carbon due to climate change shifts from near zero, which is within the range of previous model estimates, to a climate-induced loss of carbon by ecosystems in the range of 25 + -3 to 85 + -16 Pg C, depending on processes included in the model, with a best estimate of a 62 + -7 Pg C loss. Methane emissions from high-latitude regions are calculated to increase from 34 Tg CH4/y to 4170 Tg CH4/y, with increases due to CO2 fertilization, permafrost thaw, and warming-induced increased CH4 flux densities partially offset by a reduction in wetland extent
Permafrost carbon-climate feedbacks accelerate global warming
Charles D. Kovena,b,1, Bruno Ringevala, Pierre Friedlingsteinc, Philippe Ciaisa, Patricia Cadulea, Dmitry Khvorostyanovd, Gerhard Krinnere, and Charles Tarnocaif
+ Author Affiliations
aLaboratoire des Sciences du Climat et de lEnvironnement, Centre National de la Recherche Scientifique/Commissariat à lEnergie Atomique, 91191 Gif-sur-Yvette, France;
bEarth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;
cCollege of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, United Kingdom;
dLaboratoire de Météorologie Dynamique, École Polytechnique, 91128 Palaiseau, France;
eLaboratoire de Glaciologie et Géophysique de lEnvironnement, Centre National de la Recherche Scientifique/Université Joseph Fourier, Grenoble 1, Unité Mixte de Recherche 5183, F-38402 Grenoble, France; and
fAgriculture and Agri-Foods Canada, Ottawa, ON, Canada K1A 0C5
Edited* by Inez Y. Fung, University of California, Berkeley, CA, and approved July 12, 2011 (received for review March 24, 2011)
Abstract
Permafrost soils contain enormous amounts of organic carbon, which could act as a positive feedback to global climate change due to enhanced respiration rates with warming. We have used a terrestrial ecosystem model that includes permafrost carbon dynamics, inhibition of respiration in frozen soil layers, vertical mixing of soil carbon from surface to permafrost layers, and CH4 emissions from flooded areas, and which better matches new circumpolar inventories of soil carbon stocks, to explore the potential for carbon-climate feedbacks at high latitudes. Contrary to model results for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4), when permafrost processes are included, terrestrial ecosystems north of 60°N could shift from being a sink to a source of CO2 by the end of the 21st century when forced by a Special Report on Emissions Scenarios (SRES) A2 climate change scenario. Between 1860 and 2100, the model response to combined CO2 fertilization and climate change changes from a sink of 68 Pg to a 27 + -7 Pg sink to 4 + -18 Pg source, depending on the processes and parameter values used. The integrated change in carbon due to climate change shifts from near zero, which is within the range of previous model estimates, to a climate-induced loss of carbon by ecosystems in the range of 25 + -3 to 85 + -16 Pg C, depending on processes included in the model, with a best estimate of a 62 + -7 Pg C loss. Methane emissions from high-latitude regions are calculated to increase from 34 Tg CH4/y to 4170 Tg CH4/y, with increases due to CO2 fertilization, permafrost thaw, and warming-induced increased CH4 flux densities partially offset by a reduction in wetland extent
