CO2 Emissions From Rivers Draining the Tibetan Plateau Reveal Substantial Increases Over the Past 20 Years

Abstract

Inland water CO2 emissions are a critical component of the global carbon cycle, yet their magnitude and long‐term response to climate change remain poorly constrained, primarily because of uncertainties in the air–water CO2 concentration gradient. This knowledge gap is particularly pronounced on the Tibetan Plateau, where thin air and exceptional climate sensitivity complicate accurate quantification. To improve estimates of the air–water CO2 concentration gradient in this remote region, we developed an optimized, locally adapted model that explicitly accounts for the region's thin air and low atmospheric CO2 partial pressure. Our results indicate that annual riverine CO2 emissions from the Tibetan Plateau averaged ∼37 ± 3 Tg C yr−1 during 2000–2019, nearly double the previous estimate of 18.60 Tg C yr−1. Spatially, riverine CO2 emissions exhibited a distinct pattern, with lower emissions across the central plateau and higher emissions in the southeastern region, largely driven by steeper channel gradients and enhanced gas transfer velocities. Over the study period, riverine CO2 emissions increased significantly by ∼14%, corresponding to an average rate of 0.25 Tg C yr−2. This increase was closely linked to the expansion of discharge‐dependent river surface area. These findings suggest that projected climate‐driven increases in river discharge are likely to further enhance CO2 emissions from the Tibetan Plateau. The high riverine CO2 emissions and their temporal increase identified in this study also indicate an increasing role of inland waters in the regional carbon cycle, undermining efforts toward carbon neutrality.