The very top of the wire drawing represents the only part of the ocean landscape that can be seen on the surface of the water: It is Bouvet Island, one of the most isolated islands in the world.
VOA: special.2009.05.06
Clay has never been a favored surface for top American players in the professional era, but during the country's recent downturn, they've seemed positively allergic to the crushed brick.
Satellites have long been used to track ice extent (area), but calculating the thickness of the marine floes requires the overflying spacecraft to gauge the difference between the top of the ice surface and the top of the water - a relatively simple calculation then gives the overall volume.