High-Resolution Image

This is a field of "pancake" sea ice in the Bellingshausen Sea during August 2003. Diameters of the pancakes range from several tens of meters down to about a meter, and maximum thicknesses are similar. Note the smaller pancakes that have rafted on top of the larger ones, making pancake stacks. THOR (THickness from Offbeam Returns) is a lidar system with multiple fields of view, able to estimate sea ice thicknesses from an aircraft flying more than 3000 feet above the ice, by sensing the halo of light around the entry point of the laser into the ice. Outer parts of the halo are backscattered from deeper in the ice. The same system has successfully measured cloud thicknesses up to 800 meters over the Oklahoma DoE/ARM site. See http://climate.gsfc.nasa.gov/Lidar (Submitted by R. Cahalan.)