Observing seasonal bottom pressure variability in the North Pacific with GRACE

Using monthly gravity field solutions from GRACE together with output from an ocean model we assess the ability of GRACE to observe seasonal ocean bottom pressure variability in the North Pacific. First, the spatial structure and temporal evolution of the long-term mean seasonal bottom pressure cycle in the North Pacific is characterised in the context of the ocean model. It is then shown that a mean seasonal cycle based on a limited subset of the model output corresponding to the intervals over which the GRACE monthly solutions were formed is representative of this long-term seasonal cycle. It is therefore concluded that the significant features of the seasonal cycle should be present in the GRACE data. Agreement is found between the ocean model and GRACE estimates of the bottom pressure seasonal cycle, thus demonstrating the worth of GRACE as a tool for studying ocean dynamics.