Snow depth and sea ice thickness from 2009 and 2010 IceBridge ATM data in the Weddell Sea and the Bellingshausen Seas in Antarctica

IceBridge airborne measurements are intended to fill the gap in data on the elevations of the ice sheets and the sea ice covers, caused by the interval between the demise of ICESat 1's laser altimetry in 2009 and the launch of ICESat2 approximately in 2016. IceBridge LiDAR elevation measurements from aircraft are intended to provide a means of obtaining estimates of sea ice thickness and roughness with widespread application to sea ice modeling and effects of ongoing climate change. The IceBridge's Advanced Topographic Mapper (ATM) georeferenced L1B data provides elevations relative to a geoid at nominal spot size of 1-2m spaced at 5m intervals (at nadir) along track over a track swath width of 150m to 300m. Thus, in order to derive sea ice thickness and freeboard using the ATM L1B data, a local sea level reference must be established. The IceBridge's Digital Mapping System (DMS) is a digital camera that acquires high resolution natural color and panchromatic imagery from low and medium altitude. The DMS images are used to manually identify leads (open water or thin ice), where the ATM L1B elevations can be used as local sea level references. Then, the identified local sea level references are used to validate our algorithms to automatically determine the local sea level reference using the same ATM L1B data. Finally, we use the algorithm to determine the local sea level reference and thus derive the snow depth and sea ice thickness for all ATM L1B data over the Weddell Sea and the Bellingshausen-Amundsen Seas in two IceBridge missions to Antarctica in 2009 and 2010 based on an empirical relationship between snow depth and sea ice freeboard in this region.