Scientist at the University of Delaware said the huge floating mass broke free from the Petermann glacier early Thursday about 620 miles from the North Pole, a university release said.
The glacier lost about one-quarter of its 43-mile long floating ice-shelf, researchers said.
The Petermann glacier is one of the two largest glaciers in Greenland that terminate in floating shelves and connects the Greenland ice sheet directly with the ocean.
The new ice island is at least 100 square miles in area, Andreas Muenchow, associate professor of physical ocean science and engineering at the University of Delaware, said.
"The freshwater stored in this ice island could keep the Delaware or Hudson rivers flowing for more than two years. It could also keep all U.S. public tap water flowing for 120 days," Muenchow said.