Airborne freeboard measurements of sea ice and lake ice at the Sea of Okhotsk coast in 1993-95 by a laser altimeter

An airborne laser altimeter using a Nd:YAG laser was constructed to measure surface profiles of sea ice and frozen lakes. The measurements were conducted to develop a technique for estimating the ice amount of the sea ice in the Sea of Okhotsk off the northern shore of Hokkaido Island, Japan. Distributions of freeboards, mean elevations and ice concentrations were investigated from the data observed in 1993-95. Distribution functions of the ice freeboard changed considerably depending on ice concentrations in contrast with the decreasing function for the sea ice in the Arctic Ocean. The mean ice freeboard, however, correlated very well with the ice concentration, which is very important for estimating total ice amounts in regions of drifting ice. The surface roughness of a frozen lake was also observed and analysed.