The exercises train U.S. submarine crews to deal with craggy ice keels that extend 20 to 50 feet into the water, and varying salinity levels that complicate communications and navigation under the ice cap.
But even if the ice melts as fast as shippers hope (and scientists fear), navigation is likely to demand strengthened hulls, higher insurance and extra training for crews, all adding to the costs.
The button layout is also different, as it uses the standard three capacitive buttons for navigation instead of the special tablet-specific menus found in Honeycomb and Ice Cream Sandwich.