Identification and characterization of ocean mass transport and change of heat storage are important issue for better understanding of "ocean memory" for climate system, which is a key factor to clarify various climate variabilities or long-term regime shifts. In this subject, a 4D-VAR data assimilation system is executed to synthesize a variety of observations (satellite products and in-situ data such as the Argo float data) and a sophisticated general circulation model. The obtained 4-dimensional product will do for improved estimate of mass and heat transport because it exhibits dynamically self-consistency. The improved estimate of the pathway of heat and water masses definitely contributes to an important "environment section" of "the 3rd Science and Technology Basic Plan" and is suitable for the GEOSS 10-Year Implementation Plan.

In addition, application of the 4D-VAR data assimilation system to other fields is another aim of this subject, for example the interdisciplinary collaborative work with water cycle research and fisheries is now underway. Especially, the latter has a huge impact on societal activities taking into account the fact that fishery resource is the main animal protein source for human.