Scientists propose that it would be possible to measure changes in ocean mass with a single moored sensor. Changes in ocean mass, which can be caused by added water from melting ice sheets, are an important part of global sea level changes, which can also result from thermal expansion. Many estimates of changes in ocean mass currently rely on satellite-based measurements of the regional gravitational field, which are used to calculate mass. However, satellites have limited spatial resolution and have difficulty distinguishing mass on land from ocean mass near coasts. They also have problems measuring the very largest scales, making interpretation difficult.