Changing boreal methane sources and constant biomass burning during the last termination

TY - JOUR

T1 - Changing boreal methane sources and constant biomass burning during the last termination

AU - Fischer, Hubertus

AU - Behrens, Melanie

AU - Bock, Michael

AU - Richter, Ulrike

AU - Schmitt, Jochen

AU - Loulergue, Laetitia

AU - Chappellaz, Jerome

AU - Spahni, Renato

AU - Blunier, Thomas

AU - Leuenberger, Markus

AU - Stocker, Thomas F

N1 - Keywords: Atmosphere; Biomass; Carbon; Carbon Isotopes; Cold Climate; Fires; Greenland; History, Ancient; Hydrogen; Ice Cover; Methane; Monte Carlo Method; Temperature; Trees; Wetlands

PY - 2008

Y1 - 2008

N2 - Past atmospheric methane concentrations show strong fluctuations in parallel to rapid glacial climate changes in the Northern Hemisphere superimposed on a glacial-interglacial doubling of methane concentrations. The processes driving the observed fluctuations remain uncertain but can be constrained using methane isotopic information from ice cores. Here we present an ice core record of carbon isotopic ratios in methane over the entire last glacial-interglacial transition. Our data show that the carbon in atmospheric methane was isotopically much heavier in cold climate periods. With the help of a box model constrained by the present data and previously published results, we are able to estimate the magnitude of past individual methane emission sources and the atmospheric lifetime of methane. We find that methane emissions due to biomass burning were about 45 Tg methane per year, and that these remained roughly constant throughout the glacial termination. The atmospheric lifetime of methane is reduced during cold climate periods. We also show that boreal wetlands are an important source of methane during warm events, but their methane emissions are essentially shut down during cold climate conditions.

AB - Past atmospheric methane concentrations show strong fluctuations in parallel to rapid glacial climate changes in the Northern Hemisphere superimposed on a glacial-interglacial doubling of methane concentrations. The processes driving the observed fluctuations remain uncertain but can be constrained using methane isotopic information from ice cores. Here we present an ice core record of carbon isotopic ratios in methane over the entire last glacial-interglacial transition. Our data show that the carbon in atmospheric methane was isotopically much heavier in cold climate periods. With the help of a box model constrained by the present data and previously published results, we are able to estimate the magnitude of past individual methane emission sources and the atmospheric lifetime of methane. We find that methane emissions due to biomass burning were about 45 Tg methane per year, and that these remained roughly constant throughout the glacial termination. The atmospheric lifetime of methane is reduced during cold climate periods. We also show that boreal wetlands are an important source of methane during warm events, but their methane emissions are essentially shut down during cold climate conditions.

U2 - 10.1038/nature06825

DO - 10.1038/nature06825

M3 - Journal article

C2 - 18421351

SN - 0028-0836

VL - 452

SP - 864

EP - 867

JO - Nature

JF - Nature

IS - 7189

ER -