Glacier ice is a complex medium in which solar radiation exhibits both scattering and absorption. I developed a portable, rugged, photon-counting LiDAR that allows us to uncover both parameters in the field

When solar radiation and light in general interact with glacier ice, it gets scattered and absorbed. Scattering is good, because it causes most of the radiation to be reflected and it does not contribute to melt. How much radiation gets absorbed depends on both the physical structure - bubbles and ice grains - and light-absorbing impurities in the ice. Measuring these intertwined properties requires a new approach: We use a photon counting LiDAR to measure light scattered from a laser pulse. We place a sensitive detector far from the laser to measure only those photons that get scattered multiple time. Resolving the arrival time gives access to both the scattering and absorption coefficient without further models and assumtions.