Inland Water Greenhouse Gas Emissions Offset the Terrestrial Carbon Sink in the Northern Cryosphere

Climate-sensitive northern cryosphere inland waters emit greenhouse gases (GHGs) into the atmosphere, yet their total emissions remain poorly constrained. We present a data-driven synthesis of GHG emissions from northern cryosphere inland waters considering water body types, cryosphere zones, and seasonality. We find that annual GHG emissions are dominated by carbon dioxide ( 1149.2 1004.8 1307.5 teragrams of CO 2 ; median Q 1 Q 3 ) and methane ( 14.2 10.1 18.5 teragrams of CH 4 ), while the nitrous oxide emission ( 5.4 − 1.4 12.2 gigagrams of N 2 O) is minor. The annual CO 2 –equivalent (CO 2 e) GHG emissions from northern cryosphere inland waters total 1.5 1.3 1.8 or 2.3 1.8 2.8 petagrams of CO 2 e using the 100- or 20-year global warming potentials, respectively. Rivers emit 64% more CO 2 e GHGs than lakes, despite having only one-fifth of their surface area. The continuous permafrost zone contributed half of the inland water GHG emissions. Annual CO 2 e emissions from northern cryosphere inland waters exceed the region’s terrestrial net ecosystem exchange, highlighting the important role of inland waters in the cryospheric land-aquatic continuum under a warming climate.