Inland water greenhouse gas emissions offset the terrestrial carbon sink in the northern cryosphere | Science Advances

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 (

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teragrams of CO ₂ ; ) and methane ( teragrams of CH ₄ ), while the nitrous oxide emission ( gigagrams of N ₂ O) is minor. The annual CO ₂ –equivalent (CO ₂ e) GHG emissions from northern cryosphere inland waters total or 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.