Revealing recent calving activity of a tidewater glacier with terrestrial LiDAR reflection intensity

In this work we propose a method of estimating the age of calving events of a tidewater glacier based on 3D point clouds. Terrestrial LiDAR scans of the calving front of Fuerza Aerea Glacier (Greenwich Island, South Shetland Islands, Antarctica) were analyzed to determine the timing of the ice face exposure by calving events. Median reflection intensity of laser beam within a calving event footprint (I) was shown to be the best proxy measure of the ice exposure time (tLC). Point clouds were used in concert with information about calving location to create a mathematical model of the intensity-time relationship. An exponential function in the form of I = a ⋅ exp(b/tLC) + c has been shown to describe the relationship between median reflection intensity and time elapsed since the last calving event in a given part of the glacier. The model explains over 60% of the variability in reflection intensity between calving events. The shape of the model curve limits the prediction capability to events occurring up to 3 days before a scan. Development of weathered or superimposed ice on the calving scars is proposed as the explanation for increase of ice reflectivity with time.