Tibetan lakes have been persistent CO2 sources since the Last Glacial Maximum

Lakes have great contributions to global CO2 emissions, yet reconstructions of historical CO2 sources/sinks in lakes remain limited, largely due to the lack of reliable indicators. This study addresses this gap by examining CO2 concentrations and aquatic plant δ13C from 105 lakes in China. Our results demonstrate aquatic plant δ13C faithfully record CO2 concentration variations, establishing it as a reliable indicator for paleolake CO2. Building on this finding, we analyzed δ13C of aquatic plant remains in sediment cores from four Tibetan Plateau lakes. Integrating these data with published δ13C records from ten additional lakes has enabled a 26,000-year reconstruction of lake CO2 concentrations. Our integrated record reveals that Tibetan lakes have functioned as persistent CO2 sources since the Last Glacial Maximum, with enhanced emissions during the last deglaciation and early Holocene. Thus, inland lakes played a substantial role in the global CO2 cycle during the deglaciation as compared to today. Tibetan lakes have continuously released CO2 since the Last Glacial Maximum, with elevated emissions during the last deglaciation and early Holocene, as shown by reconstructed lake CO2 concentrations using stable carbon isotope records of aquatic plants from 14 lakes.