Abstract. Entropy as an important state function can be considered to provide insight into the thermodynamic properties of seawater. In this paper, the spatial-temporal distribution of specific entropy in the oceans is presented, using a new Gibbs thermodynamic potential function of seawater, which is proposed by R. Feistel. An important result is found that the distribution of specific entropy is surprisingly different from that of potential density or neutral density surfaces. By contrast, the distribution of specific entropy is quite similar to that of potential temperature in the oceans. This result is not consistent with the traditional assumption that isopycnal or isoneutral surfaces could be approximately regarded as isentropic surfaces in the physical oceanography.