Arctic Sea Ice Freeboard Retrieval With Waveform Characteristics for NASA's Airborne Topographic Mapper (ATM) and Land, Vegetation, and Ice Sensor (LVIS)

Data from an IceBridge Arctic campaign on April 20, 2010 with the Airborne Topographic Mapper (ATM) and the Land, Vegetation, and Ice Sensor (LVIS) in operation on the same airplane were used in this study. ATM and LVIS lidar waveforms were fitted with Gaussian curves to calculate pulsewidth, peak location, pulse amplitude, and signal baseline. For each waveform, the centroid, skewness, kurtosis, and pulse area were also calculated. Received waveform parameters, such as pulsewidth, pulse amplitude, pulse area, skewness, and kurtosis, show coherent response to variations of geophysical features along an ATM or LVIS profile. These parameters, combined with elevation, were used to identify leads in sea-ice freeboard calculation. The relationship between these parameters and sea-ice freeboard and surface features were studied by comparing the parameters with ATM and LVIS-derived freeboard and coincident Digital Mapping System images which have been used to classify sea-ice surface types such as leads, thin ice, gray ice, and thick ice. An elevation bias of more than 16 cm (peak-to-peak) as a function of laser scanner azimuth was found in the ATM data, and an empirical correction was applied; this correction will improve the ATM shot-to-shot freeboard significantly. The newly derived ATM freeboard was compared with the current IceBridge IDCSI2 freeboard product at National Snow and Ice Data Center (NSIDC) and the freeboard derived from LVIS data. Over the studied area, the mean freeboard is 0.540 $\pm$ 0.091 m for the IDCSI2 at NSIDC, 0.496 $\pm$ 0.062 m for the ATM after empirical elevation correction, and 0.509 $\pm$ 0.048 m for the LVIS.