Shallow water tides in the northwest European shelf region from TOPEX/POSEIDON altimetry

During recent years the accurate measurements from the TOPEX/POSEIDON satel lite have improved global ocean tide models considerably. However, these gl obal ocean tide models are still not accurate enough on the continental she lves for detailed oceanographic studies. The need for increasing accuracy i n shelf regions calls for inclusion of more than just semidiurnal and diurn al constituents in future global ocean tide models. This is because a consi derable part of the tidal variability on the shelves is caused by shallow w ater constituents. One example is the M-4 constituent, which exceeds 50 cm at several locations on the northwest European shelf. So far, TOPEX/POSEIDO N has not been considered for resolving these constituents, mainly owing to its coarse ground track resolution. Reliable empirical estimates of severa l major shallow water constituents can be obtained from TOPEX/POSEIDON by c ombining along-track and crossover observations. Estimates of the major sha llow water constituents for the northwest European shelf, M-4, M-6, and MS4 , are presented in this study and compared with tide gauges and existing hy drodynamic models.