High‐frequency observations of melt effects on snowpack stratigraphy, Kahiltna Glacier, Central Alaska Range

With an increased volume of melt on many of the world's glaciers, study of how meltwater affects the properties of glacial snowpack becomes essential to our understanding of how glaciers will respond to climate change. We address this problem by studying how snow properties changed on sub‐daily timescales on the Kahiltna Glacier, Alaska, between May 26 and June 10, 2010. During this period, we dug 1.8‐m‐deep snow pits twice daily to record the stratigraphy of melt layers, snow hardness, grain size, and density and sampled for hydrogen isotopic composition (δD) on four occasions. From these data, we show that 65% of the melted surface snow infiltrates and refreezes in the snowpack. This leads to a densification of the snow, a 729% increase in volume of melt layers, and a homogenization of isotopic and physical snow properties. From visual and stratigraphic observations, we show that meltwater flow within the snowpack is conducted primarily along lenses and pipes, where melt layers later form, but that more homogeneous capillary‐based flow is also important. Finally, we show using isotope ratios that post‐depositional alteration is exacerbated with increased melt extent, using the δD profile below a volcanic ash layer as a case study. In the future, similar studies would benefit from this high‐frequency monitoring approach to assessing snowpack evolution, as it allows for a greater understanding of short duration processes. New directions for study would include longer‐term monitoring efforts over a wider spatial snow pit network. Copyright © 2012 John Wiley & Sons, Ltd.