Physical characteristics of summer sea ice across the Arctic Ocean

Sea ice characteristics were investigated during July and August on the 199 4 transect across the Arctic Ocean. Properties examined from ice cores incl uded salinity, temperature, and ice structure. Salinities measured near zer o at the surface, increasing to 3-4 parts per thousand at the ice-water int erface. Ice crystal texture was dominated by columnar ice, comprising 90% o f the ice sampled. Surface albedos of various ice types, measured with radi ometers, showed integrated shortwave albedos of 0.1 to 0.3 for melt ponds, 0.5 for bare, discolored ice, and 0.6 to 0.8 for a deteriorated surface or snow-covered ice. Aerial photography was utilized to document the distribut ion of open melt ponds, which decreased from 12% coverage of the ice surfac e in late July at 76 degrees N to almost none in mid-August at 88 degrees N . Most melt ponds were shallow, and depth bore no relationship to size. Sed iment was pervasive from the Southern Chukchi Sea to the north pole, occurr ing in bands or patches. It was absent in the Eurasian Arctic, where it dad been observed on earlier expeditions. Calculations of reverse trajectories of the sediment-bearing floes; suggest that the southernmost sediment was entrained during ice formation in the Beaufort Sea while more northerly sam ples probably originated in the East Siberian Sea, same as far west as the New Siberian Islands.