We have composited and objectively analyzed hiostorical hydrographic observations for the North Atlantic Ocean for two periods, 1955--1959 and 1970--1974. Difference fields of steric sea level and geopotential thickness for the North Atlantic Ocean in the 0- to 1500-m depth range between the 1955--1959 and 1970--1974 pentads were computed. We find that in the central portion of the subtropical gyre, steric sea level decreased by up to 17.5 dyn cm, whereas in the western subarctic gyre (north of the Gulf Stream) steric sea level increased by an amount up to 7.5 dyn cm from earlier to the later pentad. A decrease in steric sea level (~5 dyn cm) occurred along the eastern boundary of the North Atlantic. ¿ American Geophysical Union 1990