O18/O16 data on a depth profile of water samples from the Arctic Ocean reveal that near surface water is depleted in O18 by about 4‰, but water at depths greater than 350 meters reaches near normal open ocean water composition. The O18 profile very closely follows the salinity profile, with δO18 changing by about 0.8‰ per 1‰ salinity change. The results of δO18 measurements on the pelagic species Globigerina pachyderma from a composite core show that the δO18 value has not changed since the latter part of the last glacial period. This constancy we take to indicate that the temperature and the δO18 value of the water in which these foraminifera grew have not changed significantly since that time. Such a conclusion seems to imply that the present ice coverage in the Arctic Ocean has remained unchanged during the last 25,000 years. However, the δO18 value of benthonic foraminifera shows a shift of 1.2‰ between the end of the last glacial period and the present warm period. This shift is consistent with the idea that the deep water mass of the Arctic Ocean is formed outside the Arctic basin. The information on the δO18 value of the benthonic foraminifera from the top of the core was used in conjunction with the data on δO18 and temperature of the bottom water to establish the constant in the empirical equation relating δO18 values to temperature for the preparation procedure used in our laboratory. Based on this calibration, the data confirm A. W. H. Bé's contention (personal communication, 1960) that G. pachyderma incorporates about one-half of its CaCO3 below 300 meters. Copyright 1969 by the American Geophysical Union.
