Ice sheets and glaciers have been shown to deliver large amounts of labile dissolved organic carbon (DOC) to downstream aquatic ecosystems, but recent studies may underestimate the release of DOC from mountain glaciers. To date, continuous measurements of DOC from mountain glaciers throughout entire glacier melt season are very limited. Here we present high-density data on DOC from two Asian mountain glaciers over a full melt season in 2013 and compile a global data set of DOC from 42 mountain glaciers. Based on our study and previously published DOC data, we estimate the storage and release of DOC associated with Asian mountain glaciers to be 8.8 to 13.8 Tg C and 0.19 Tg C/a, respectively. Rough extrapolation of glacier runoff to a global scale suggests that DOC release from mountain glaciers is on the order of 0.8 Tg C/a, which is 1.4 times higher than the most current estimates. The current release of DOC from mountain glaciers is therefore far more significant than previously thought and should be considered in future evaluation of the global carbon cycle.

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