The Earth's varying rotation is measured by a number of space geodetic techniques, individually or in combination. The results are reckoned as the Earth orientation parameters (EOP), which result from the intersection of the terrestrial, Earth fixed, and the celestial, space-fixed, reference frames. Conventionally, variations of the EOP are expressed by 5 parameters to describe precession/nutation, the rate of change of axial rotation, and polar motion. As the accuracy and the temporal resolution of the EOP determinations have steadily improved over recent years, we have been seeking more detailed explanations for their excitations. Besides tidal influences from outside the Earth, the principal causes for variable EOP appear to be related to the changing motions and mass distribution of the fluid portions of the planet. Observations of the geophysical fluids, such as the atmosphere, oceans, and other hydrological reservoirs, have achieved a new maturity, as they are typically combined within the context of dynamically designed fluid models, often through optimal methods of data assimilation. Independent observations of the relevant mass fields include the result of novel gravity missions like GRACE as well. Besides the view of contemporary determination of the EOP and the related geophysical excitations, are forecasts of these quantities, important in practical matters of determining Earth position for spacecraft navigation. We seek contributions to this session that highlight new determinations of EOP series and their analyses, and new developments concerning the dynamical basis for the links between the Earth rotation, geophysical fluids, and other geodetic quantities related to the Earth gravity field or surface deformation. These may include results from special monitoring campaigns, such as CONT08 in August 2008, that have focused on intense observations of Earth rotation and related parameters, as well as the geophysical signals related to them. We also welcome discussion of the relationship between Earth orientation parameters variability and current or potential variability in fluids due to climate variation or global change signals. In addition, we will welcome input on the characteristics and variability of (nonterrestrial) planetary rotation parameters of other planets or planetary bodies.