Coastal Applications for High-Resolution Altimetry

The scales of mesoscale features in sea surface height (SSH) that can be resolved by fields constructed by 2- 4 altimeters are of the order of 50-100km. These scales are much larger than the features considered by traditional coastal oceanography, which examines the region over the continental shelves, which can be 10- 200km wide. Even over wide shelves, however, circulation features occur across narrow (10km or less) fronts, such as upwelling fronts, shelf break fronts, etc. For upwelling fronts over narrow (10-40km) shelves, as found off the western U.S. and other upwelling regions, an additional problem is the gap in data from standard altimeters next to the coast, which can also be 10-40km. Here we illustrate several examples of these structures and apply two modifications to the normal altimeter analyses. First, we combine multiple altimeters with coastal tide gauge data to bridge the coastal gap in data. Second, we use the high-frequency 10-Hz (T/P) and 20-Hz (Jason-1 data in the near-coast region off Oregon to attempt to resolve narrow SSH gradients that correspond to the SST gradients caused by upwelling. The along-track resolution of these high-frequency SSH data is similar to the highest 2-D resolution that is expected from future Wide-Swath Altimeters, providing an initial indication of what we might expect from the future sensors.