We used gradient criteria to establish a global ocean mixed layer depth (MLD), thermocline depth (THD), and thermocline strength (THS) data sets from the National Oceanographic Data Center (NODC) 4.5 million temperature profiles. The annual cycles of MLD, THD, and THS of the world ocean are described based on climatological monthly-mean MLD fields. The interannual variabilities of MLD, THD, and THS are obtained from zonally averaged monthly mean fields as well as the latitudinally averaged (10 deg N and 10 deg S) monthly mean fields. The ocean interannual thermal variability is closely related to El Nino, North Atlantic Oscillation (NAO), and Great Salinity Anomaly in the Arctic regions.