This data set consists of sea ice measurements including thickness, salinity, and stable isotope composition from the Laptev Sea. The data were obtained during the Transdrift VI expedition to the Laptev Sea in April and May of 1999 as part of a project supported through the National Science Foundation (NSF) Arctic System Science (ARCSS) Program. Sea ice cores were obtained with a 10 cm diameter ... corer. Ice thickness was measured in centimeters at the site with a tape measure. On-site, 2 cm thick horizontal sections were cut approximately every 10 cm down the core. Salinity of each sample was determined in practical salinity units (psu) using a salinity, conductivity, and temperature meter with an error of less than 0.02 or 1 percent of bulk salinity. Oxygen stable isotope (delta oxygen-18, or delta 18-O) measurementsts were then performed at the Stable Isotope Laboratory (Department of Physics and Astronomy, University of Calgary, Calgary, Canada) on a mass spectrometer at a precision of better than 0.4 parts per thousand, (ppt, 103). Data are in a comma-separated variable ASCII format, and are available for download via FTP. Data are compiled for each coring location, though stable isotope measurements were not obtained for all samples.