A remnant of Taylor Glacier ice rests beneath a 40–80 cm thick layer of sublimation till in central Beacon Valley, Antarctica. A vapour diffusion model was developed to track summertime vapour flow within this till. As input, we used meteorological data from installed HOBO data loggers that captured changes in solar radiance, atmospheric temperature, relative humidity, soil temperature, and soil moisture from 18 November 2004–29 December 2004. Model results show that vapour flows into and out of the sublimation till at rates dependent on the non-linear variation of soil temperature with depth. Although measured meteorological conditions during the study interval favoured a net loss of buried glacier ice (∼0.017 mm), we show that ice preservation is extremely sensitive to minor perturbations in temperature and relative humidity. Net loss of buried glacier ice is reduced to zero (during summer months) if air temperature (measured 2 cm above the till surface) decreases by 5.5°C (from −7°C to −12°C); or average relative humidity increases by 22% (from ∼36% to 58%); or infiltration of minor snowmelt equals ∼0.002 mm day−1. Our model results are consistent with the potential for long-term survival of buried glacier ice in the hyper-arid stable upland zone of the western Dry Valleys.