Retrieval of Sea Ice Freeboard from ICESat-2 Multi-beam Altimetry

Abstract:

We illustrate our approach for retrieval of sea ice freeboard in height measurements from the multi-beam lidar on ICESat-2, using data acquired by a Multiple Altimeter Beam Experimental Lidar (MABEL). Prior to launch, MABEL serves as an airborne implementation for testing and algorithm development. Thus far, acquired data sets include flights over Arctic sea ice from the spring and summer: one in April 2012 (north of the Arctic coast of Greenland, and the other in the East Greenland Sea) and the other in July 2014 (Beaufort Sea). Here, we briefly describe the phenomenology of photon distributions in the sea ice returns and our approach for finding the heights of the ice and water surfaces, and the achievable height precision is discussed. Retrieved surface heights over relatively flat leads in the ice cover suggest that precisions of several centimeters are attainable. Comparisons of nearly coincident elevation profiles from MABEL with those acquired by an analog lidar show good agreement. Discrimination of ice and open water, a crucial step in the determination of sea ice freeboard and the estimation of ice thickness, is facilitated by contrasts in the observed signal/background photon statistics.