Inland water greenhouse gas emissions offset the terrestrial carbon sink in the northern cryosphere
Chunlin Song, Shaoda Liu, Genxu Wang, Liwei Zhang, Judith A. Rosentreter, Gang Zhao, Xiangyang Sun, Yuanzhi Yao, Cuicui Mu, Shouqin Sun, Zhaoyong Hu, Shan Lin, Juying Sun, Li Yang, Ying Wang, Yuhao Li, Peter A. Raymond, Jan Karlsson
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 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mn>1149.2</mml:mn> <mml:mn>1004.8</mml:mn> <mml:mn>1307.5</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> teragrams of CO 2 ; <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mtext>median</mml:mtext> <mml:mrow> <mml:mi mathvariant="normal">Q</mml:mi> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">Q</mml:mi> <mml:mn>3</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> ) and methane ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mn>14.2</mml:mn> <mml:mn>10.1</mml:mn> <mml:mn>18.5</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> teragrams of CH 4 ), while the nitrous oxide emission ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mn>5.4</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.4</mml:mn> </mml:mrow> <mml:mn>12.2</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> gigagrams of N 2 O) is minor. The annual CO 2 –equivalent (CO 2 e) GHG emissions from northern cryosphere inland waters total <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mn>1.5</mml:mn> <mml:mn>1.3</mml:mn> <mml:mn>1.8</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> or <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mn>2.3</mml:mn> <mml:mn>1.8</mml:mn> <mml:mn>2.8</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> 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.