Decadal shifts in Qingzang Plateau lake carbon dynamics (1970-2020): From predominant carbon sources to emerging sinks.

ABSTRACT

The evasion of carbon dioxide (CO2) from lakes significantly influences the global carbon equilibrium. Amidst global climatic transformations, the role of Qingzang Plateau (QZP) lakes as carbon (C) sources or sinks remains a subject of debate. Furthermore, accurately quantifying their contribution to the global carbon budget presents a formidable challenge. Here, spanning half a century (1970-2020), we utilize a synthesis of literature and empirical field data to assess the CO2 exchange flux of QZP lakes. We find markedly higher CO2 exchange flux in the southeast lakes than that in the northern and western regions from 1970 to 2000. During this time, both freshwater and saltwater lakes served primarily as carbon sources. The annual CO2 exchange flux was estimated at 2.04 ± 0.37 Tg (Tg) C yr-1, mainly influenced by temperature fluctuations. The CO2 exchange flux patterns underwent a geographical inversion between 2000 and 2020, with increased levels in the west and decreased levels in the east. Notably, CO2 emissions from freshwater lakes diminished, and certain saltwater lakes in the QTP transitioned from carbon sources to sinks. From 2000 to 2020, the annual CO2 exchange flux from QZP lakes is estimated at 1.34 ± 0.50 Tg C yr-1, with solar radiation playing a more pronounced role in carbon emissions. Cumulatively, over the past five decades, QZP lakes have generally functioned as carbon sources. Nevertheless, the total annual CO2 emissions have declined since the year 2000, indicating a potential shift trend from being a carbon source to a sink, mirroring broader patterns of global climate change. These findings not only augment our understanding of the carbon cycle in plateau aquatic systems but also provide crucial data for refining China's carbon budget.