| Summary: | Recent studies of Greenland Ice Sheet mass balance indicate that the ice sheet is shrinking and contributing to sea level rise. This is driven in part by increases in surface melting, however, not all melt water generated during the summer leaves the ice sheet. A significant quantity of surface melt water refreezes within the firn creating uncertainty in surface mass balance estimates. This refreezing has the potential to buffer future sea level rise to future increases in melting, but direct measurement of the process remains difficult. We present a method for quantifying refreezing at point locations using firn temperature profiles. Firn temperatures from a transect of 11 sites in the accumulation zone of Greenland were collected over the course of two melt seasons from 2007 to 2009. We use conservation of energy to isolate the heat released by refreezing from seasonal temperature changes and high resolution heat flux estimates. Results indicate there is deep infiltration of melt water and possibly significant lateral flow of water through the firn. Furthermore, a lack of these hydrological processes in most current models of surface mass balance may cause these models to be inadequate at predicting refreezing.
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