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.
Above-freezing temperatures also led to overflow along the trail, a potentially dangerous situation where water has pushed up through the ice and refrozen, creating a weak top layer of ice that teams and mushers can break through.
