Recent Increase in Seasonal Amplitudes of CO2 and δ13CO2 Over Canada and Their Implications
L. Huang1, Y. Lee2, D. Worthy1, E. Chan1 and D. Chan1
1Environment Canada, Climate Research Division, Atmospheric Science Technology Directorate/STB, Toronto, Canada; 416-739-5821, E-mail: email@example.com
2Korea Astronomy and Space Science Institute (KASI), Daejeon, Korea
High precision CO2 and δ13CO2 measurements of flask samples were carried out by Environment Canada for Alert, NU (82°27'N, 62°31'W, ) and Fraserdale, ON (49°53'N, 81°34'W) during the period of 1998 – 2010 and 2003-2010, respectively. Alert (World Meteorological Organization/Global Atmosphere Watch site) is a Northern Hemisphere background site, whereas Fraserdale is a representative site of boreal forest in Eastern Canada. A digital filtering approach was applied to the discrete signals of flask CO2 and δ13CO2 measurements. Seasonal amplitudes (SA) have been obtained in both CO2 and δ13CO2, based on photosynthesis dominant and respiration dominant processes. The results are comparable with those by two other previously published curve-fitting methods. The SA mean values of CO2 and δ13CO2 are ~ 16.2ppm and ~ 0.8 ‰ at the background site and ~ 21.8ppm and ~ 1.1‰ at the boreal forest site, respectively, for the period of 2003-2009. Increases in SAs of CO2 and δ13CO2 were observed at both sites during the period. Although the size of the increase is different between the two sites, the mean relative increase rates for CO2 and δ13CO2 are similar, ranging between 2-3 % /yr, suggesting that the terrestrial biosphere in the Northern mid-high latitudes was working more actively during the period of 2003 through 2009, in comparison with the previous years (see Figures below). The ratio of [the mean increased CO2]/[the mean increased δ13CO2] at Alert is obviously different from that at Fraserdale, inferring that the dominant sources causing the increases of SAs at the two sites could be different. Further analysis shows that the observed variations in SA of CO2 and δ13C at the boreal forest site are correlated with summer/fall (May – October) temperatures as well as winter/spring (November – April) precipitation, indicating possible regional climate response of terrestrial biosphere carbon cycle.