Time-lapse thermal imagery used to resolve sub-debris glacier melt in Alaska


Rock debris at the surface of a glacier often insulates the underlying ice from incoming energy fluxes thereby reducing the local melt rate. The relation between debris thickness and melt suppression is nonlinear and consistent throughout many field studies. Debris that is about 10-15 cm thick can reduce the local melt rate by half and debris >50 cm thick can reduce melt to near zero. The distribution of debris cover on glaciers globally is not explicitly known at the time of writing, but is estimated at around 17%. The impact of debris cover on glacier melt is neglected in most large-scale glacier melt models and is likely one of the leading sources of error. The spatial distribution of debris on glaciers is fairly simple to derive from remote sensing, yet the governing term, the thickness of the debris, is much more difficult to resolve. We use time-lapse thermal imagery collected in the Alaska Range coupled with classical glacier field data and satellite based thermal imagery to (1) test the hypothesis that thermal data can be used to derive debris thickness at wide spatial scales, and (2) develop a simple model for estimating the impact of debris cover on glacier melt at a regional scale. Modeling efforts that are successful at a regional scale are an essential step towards larger-scale efforts. This work is targeted towards the inclusion of a debris cover term in global glacier melt models.

Davos, Switzerland