Polar Science ( IF 1.389 ) Pub Date : 2020-07-31 , DOI: 10.1016/j.polar.2020.100553 Shinji Morimoto; Daisuke Goto; Shohei Murayama; Ryo Fujita; Yasunori Tohjima; Shigeyuki Ishidoya; Toshinobu Machida; Yoichi Inai; Prabir K. Patra; Shamil Maksyutov; Akihiko Ito; Shuji Aoki
To understand the spatio-temporal variations of the atmospheric greenhouse gases in the Arctic region, we have conducted systematic observations and numerical model simulations. Long-term observations for CO2, CH4 and related constituents at Ny-Ålesund helped in separating the oceanic and terrestrial uptake rates of CO2 and revealed the importance of biogenic CH4 emissions to atmospheric CH4 variations. Shipboard observations of atmospheric CH4 in the Arctic Ocean indicated several peaks associated with long-range transports of the continental source signals. An underestimation of climatological O2 flux is demonstrated by the shipboard O2/N2 observations over the North Pacific and Arctic Sea. Clear seasonal cycles and long-term trends of the greenhouse gases were observed in the upper troposphere and lower stratosphere over the Eurasian continent at 8.5–12.5 km in altitude. Forward and inverse modeling studies and direct observations of CH4 emission from West Siberian wetlands were conducted to evaluate the CH4 fluxes estimated by previous bottom-up studies. To be consistent with the atmospheric CH4 observations, the prescribed CH4 emission needs downward and upward revisions at Hudson Bay Lowland and West Siberia, respectively. The terrestrial ecosystem model study showed increasing trends in the CH4 emission in inland North America, Alaska and northern part of West Siberian Lowland.