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

Abstract

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 CO₂; ${\text{median}}_{Q1}^{Q3}$) and methane (${14.2}_{10.1}^{18.5}$ teragrams of CH₄), while the nitrous oxide emission (${5.4}_{-1.4}^{12.2}$ gigagrams of N₂O) is minor. The annual CO₂–equivalent (CO₂e) GHG emissions from northern cryosphere inland waters total ${1.5}_{1.3}^{1.8}$ or ${2.3}_{1.8}^{2.8}$ 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.