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 ([Formula: see text] teragrams of CO₂; [Formula: see text]) and methane ([Formula: see text] teragrams of CH₄), while the nitrous oxide emission ([Formula: see text] gigagrams of N₂O) is minor. The annual CO₂-equivalent (CO₂e) GHG emissions from northern cryosphere inland waters total [Formula: see text] or [Formula: see text] petagrams of CO₂e using the 100- or 20-year global warming potentials, respectively. Rivers emit 64% more CO₂e 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 CO₂e 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.