Scientific American: The rare ships that have ventured through the harsh, icebound Arctic Ocean require reinforced hulls and ice-breaking bows that allow them to plow through dense ice as much as two meters deep, and face hazardous conditions in remote locations for long periods of time. Arctic sea ice now is melting so rapidly each summer due to global warming, however, that ships without ice-breaking hulls will be able to cross previously inaccessible parts of the Arctic Ocean by 2050. And light-weight ships equipped...