LiveScience: New York, Boston, Halifax and other cities in the northeastern United States and Canada could come under greater threat from sea level rise due to melting of the Greenland ice sheet this century, a new study suggests. Greenland is the world’s largest island, covering an area more than three times the size of Texas. Some 81 percent of it has been permanently capped by ice, with many glaciers that slowly move ice out sea. The new study, detailed in the May 29 issue of the journal …