Earth orientation parameters (EOP) are measured with very high accuracy. Changes in the EOP originate inmovements of mass within the Earth system. Therefore, these changes represent a good way of distinguishingeustatic (mass) and steric (volume) effects in sea level change. We were able to assimilate measured EOP into aglobal circulation model of the oceans. By simultaneously assimilation of oceanographic data as SSH and oceantemperatures into an model conclusions about the ocean heat content can be drawn. On interannual timescales themodel shows realistic behavior and succeeds in reproducing the EOP observations. The biggest impact is on thetotal ocean mass variation.