Oceanography Fun Fact of the Week

Satellites can only see the surface of the ocean. Nonetheless, microwave satellite instruments have been used to create a map of the sea floor.

The strength of gravity at the ocean's surface depends on the topography of the sea floor (also known as bathymetry). An underwater mountain thousands of feet high would create a hump in the surface of the ocean , perhaps two or three feet high, due to enhanced gravity; a trench would cause a depression in the sea surface.

Satellite instruments can measure surface height to within about 4 centimeters. After subtracting out other factors that affect local sea level (currents, tides, waves, atmospheric pressure) a reasonably accurate map of the ocean floor can be inferred from the shape of the sea surface. Sonar techniques are more accurate, but generate data for only a small portion of the ocean at a time, and there are many regions of the ocean for which no such data is available.

Bonus fact: Bull sharks have the highest testosterone levels of any shark species. At least according to the latest issue of People magazine.