Ocean numerical models have become quite realistic over the past sever
al years as a result of improved methods, faster computers, and global
data sets. Models now treat basin-scale to global domains while retai
ning the fine spatial scales that are important for modeling the trans
port of heat, salt, and other properties over vast distances. Simulati
ons are reproducing observed satellite results on the energetics of st
rong currents and are properly showing diverse aspects of thermodynami
c and dynamic ocean responses ranging from deep-water production to El
Nino. Now models can represent not only currents but also the consequ
ences for climate, biology, and geochemistry over time spans of months
to decades. However, much remains to be understood from models about
ocean circulation on longer time scales, including the evolution of th
e dominant water masses, the predictability of climate, and the ocean'
s influence on global change.