The Canadian
Greenhouse Gas Measurement Program operates stations that precisely monitor
atmospheric levels of greenhouse gases (GHGs) carbon dioxide (CO2), methane
(CH4), and nitrous oxide (N2O) in all regions of the country. The most remote
site, at Alert, Nunavut, contributes measurements to the Global Atmosphere
Watch Programme of the World Meteorological Organization, which tracks changes
in global GHG concentrations. Northern Hemisphere GHG concentrations, such as
those observed at Canadian sites, are slightly higher than the global average
because of larger sources of emissions in the Northern Hemisphere. The
long-term trends from all Canadian sites closely track the increasing global
CO2 concentration trend, while also showing clear seasonal cycles of CO2
concentration due to photosynthesis (plants remove CO2 from the atmosphere) and
biogenic respiration (plants and animals breathe out CO2).
Canadian
monitoring sites are also used to track changes in regional GHG emissions and
removals due to the impact of the changing climate on vulnerable ecosystems,
such as the tundra and boreal forest. The vast Canadian boreal forest (2.7
million km2) typically takes up a net 28 megatonnes of carbon from the
atmosphere per year (Kurz et al., 2013). Fraserdale, situated close to the
boreal forest, is influenced quite strongly by forest processes that affect
atmospheric CO2 levels. Lower concentrations of CO2 are evident in summer
(dominated by photosynthesis) and higher concentrations are evident in winter
(dominated by respiration) compared with the more distant site at Alert that is
not surrounded by significant vegetation. Research has found that the net
amount of carbon taken up in the Canadian boreal forest has increased in warmer
years (Chen et al., 2006). In contrast, studies in Scandinavian boreal forests
have found that the net uptake of carbon has decreased in recent years (i.e.,
1999–2013) (Hadden and Grelle, 2016). This highlights the value of performing
specific atmospheric observations in the Canadian boreal forest. Furthermore,
atmospheric observations of CH4 in the Arctic could detect any rapid changes in
emissions due to thawing of permafrost.
In summary,
atmospheric observations play a key role in tracking global trends in GHG
concentrations, in monitoring changes resulting from global GHG mitigation
efforts, and in understanding the climate feedback of Canadian ecosystems.
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