Magnitude and seasonality of wetland methane emissions from the Hudson Bay Lowlands (Canada) 1School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, Cambridge MA 02138, USA
27 Apr 2011
2NASA Langley Research Center, Hampton, Virginia, USA
3Environment Canada, Toronto, Ontario, Canada
4Environmental Engineering Institute, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
5Center for Climate Systems Modeling (C2SM), ETH Zürich, Universitätstrasse 16, Zürich, Switzerland
6Laboratoire de Modélisation de Chimie Atmosphérique, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
*current address: CSIRO – Marine and Atmospheric Research, GPO Box 3023, Canberra, ACT, 2601, Australia
Received: 02 Aug 2010 – Published in Atmos. Chem. Phys. Discuss.: 30 Sep 2010Abstract. The Hudson Bay Lowlands (HBL) is the second largest boreal wetland ecosystem
in the world and an important natural source of global atmospheric methane.
We quantify the HBL methane emissions by using the GEOS-Chem chemical
transport model to simulate aircraft measurements over the HBL from the
ARCTAS and pre-HIPPO campaigns in May–July 2008, together with continuous
2004–2008 surface observations at Fraserdale (southern edge of HBL) and
Alert (Arctic background). The difference in methane concentrations between
Fraserdale and Alert is shown to be a good indicator of HBL emissions, and
implies a sharp seasonal onset of emissions in late May (consistent with the
aircraft data), a peak in July–August, and a seasonal shut-off in September.
The model, in which seasonal variation of emission is mainly driven by
surface temperature, reproduces well the observations in summer but its
seasonal shoulders are too broad. We suggest that this reflects the
suppression of emissions by snow cover and greatly improve the model
simulation by accounting for this effect. Our resulting best estimate for
HBL methane emissions is 2.3 Tg a−1, several-fold higher than previous
estimates (Roulet et al., 1994; Worthy et al., 2000).
Revised: 29 Mar 2011 – Accepted: 30 Mar 2011 – Published: 27 Apr 2011
Citation: Pickett-Heaps, C. A., Jacob, D. J., Wecht, K. J., Kort, E. A., Wofsy, S. C., Diskin, G. S., Worthy, D. E. J., Kaplan, J. O., Bey, I., and Drevet, J.: Magnitude and seasonality of wetland methane emissions from the Hudson Bay Lowlands (Canada), Atmos. Chem. Phys., 11, 3773-3779, doi:10.5194/acp-11-3773-2011, 2011.