Variations of vertical profiles of sea ice temperature, and adjacent atmosphere and ocean temperatures were measured by ice drifting buoys deployed in the northeast Chukchi Sea, as part of the 2003 Chinese Arctic Research Expedition. The buoy observations (September 2003 to February 2005) show that the cooling of the ice began in late September, propagated down through the ice, reaching the bottom of the ice in December, and continued throughout the winter. In winter 2003/2004, some obvious warmings were observed in the upper portion of the ice in response to major warmings in the overlying atmosphere associated with the periodicity of storms in the northeast Chukchi Sea. It is found that the melt season at the buoy site in 2004 was about 15% longer than normal. The buoy observed vertical ice temperature profiles were also used as a diagnostic for sea ice model evaluation. The results show that the simulated ice temperature profiles have large discrepancies as compared to the observations.