Higher, but more variable, annual CO2 emissions from lakes in drier Arctic landscapes

Abstract Land-to-water hydrological connections represent a key regulatory mechanism of carbon transport, controlling carbon dioxide (CO 2 ) emissions from lakes; however, as of yet, there is no assessment of its role at a pan-Arctic scale across large climatic and topographical gradients. We hypothesized that hydrologically well-connected lakes in wetter regions are CO 2 sources fueled by stronger lateral fluxes of external carbon relative to drier regions. However, based on data from >200 Arctic lakes, we found that lakes in drier regions have higher and more variable annual CO 2 emissions ( $${37.0}_{6.2}^{146.0}$$ 37.0 6.2 146.0 gC m -2 yr -1 , $${{median}}_{Q1}^{Q3}$$ m e d i a n Q 1 Q 3 ) compared to lakes in wetter regions ( $${8.0}_{1.7}^{17.3}$$ 8.0 1.7 17.3 gC m -2 yr -1 ), with both the lowest and the highest fluxes recorded among dryland lakes. We hypothesize that with increasing wetness, the relative proportion of fluvial emissions increases, whereas in drier landscapes where lakes often have limited stream export, carbon inputs can be retained and more efficiently emitted from lakes.