The oceans cover about 71 per cent of the Earth's surface. Due to their enormous ability to store heat, the oceans play a key role in the global redistribution of the energy absorbed by the sun. In this way the oceans on the one hand compensate seasonal temperature fluctuations in the atmosphere and on the other hand, influence the climate system of the Earth over periods up to several ten thousands of years. The only slow reaction of the climate to changed greenhouse gas emissions is also essentially due to the inertia of the oceans.
As a consequence, climate changes can only be understood and evaluated with extensive knowledge of ocean current systems and their effect on the global climate system. In contrast to traditional in-situ methods, satellite-based observations do not permit direct measurements of three-dimensional ocean currents and their variability but they do allow an almost global recording of the large-scale distribution of specific parameters such as sea level using radar altimetry or oceanic mass distribution inferred from gravity field missions.
However, the application of various analysis methods and complementary numerical models enable us to derive detailed information about global ocean circulation from such precise geodetic monotoring data. Modern geodetic satellite observations therefore offer an immense, albeit not yet fully exploited potential for extensive and almost continuous recording of ocean currents.
