quite irregular (it sometimes leads to a "Loop Current"). 

 Presumably satellites could determine the onset of the 

 Somali Current, and others. 



It has been pointed out by Greenwood et al. (1969) 

 that a satellite leaving the east coast of the United States 

 passes over strong topography of the Geoid. A Gulf- Stream 

 "signal", one meter in elevation and 100 km wide, will be 

 superposed on the much larger features of the Geoid. Where 

 the Gulf Stream is close to the coast and more nearly 

 constant in position, the airborne infra-red surveys can 

 point out its position. Farther from the coast, however, 

 the large meanders will be not steady features. Over 

 the course of many satellite passes these time-dependent 

 features will be separable from the "background" shape 

 of the Geoid. Although the meanders can remain in a fixed 

 position for short times, they usually change position 

 substantially during a time scale of perhaps two weeks. 

 It is apparent that the satellite must reach latitudes 

 as far north as 40° to 42° to be useful for this purpose. 



Eastern boundary currents, such as the California Current, 

 have a much smaller signal than western boundary currents, 

 so that it may not be feasible to track them by the 

 altimeter; it would be interesting to try. The change in 

 level is only about 1/3 that of a western boundary current, 

 and the width is 5 to 10 times greater. Wooster and 

 Reid (1963) give averages of 34 cm and 1000 km for the 

 change in elevation, and width. 



Slope of sea level along coasts . The next area in which 

 the satellite altimetry results could make contributions 

 to oceanography concerns the problem of the slope of sea 

 level along the coasts. Since the 1920 's it has been known 

 from precise leveling on land that mean sea level appears 

 to rise from south to north. Braaten and McCombs (1963) 

 have shown the results of a special leveling adjustment. 

 They found that the coastal rise of sea level, as indicated 

 by the leveling, is approximately 60 cm on both the east 

 coast and the west coast of the United States. They also 

 show that mean sea level on the Pacific coast of the U.S. 



24-11 



