Asked by: Stephan Savilaakso, Glasgow
Yes it is. If we ignore tides, winds and waves for a moment, it turns out the ocean surface isn’t uniformly flat. The water dips and swells according to the topography of the sea bed beneath. The reason is gravity. A large feature like an underwater volcano attracts water towards it, causing a slight bump. The slope would be too gradual to see from a ship, but satellite altimeters – capable of accurately gauging distance down to the ocean surface – can detect and measure these variations. They use microwave radio, timing the interval between transmitting a short pulse and receiving a reflection back from the sea surface. An array of ground-based laser radar stations also tracks the satellites, giving their precise location and altitude. Through satellite oceanography, surface maps have been created that would take years to construct through the conventional bathymetry means of vessels mapping the floor through echo sounding.