A new study shows one of the largest glaciers  in Greenland is becoming smaller and speeding to the sea faster than scientists expected. If it continues, Greenland itself could become much smaller during this century and global seas could rise as much as 3 feet. The rates of change that we're noticing are much higher than expected. If these rates continue, it is not likely that Greenland could shrink by several tens of percent this century. However, it's not known how quickly this coastal response of the Greenland ice sheet melting will have an effect on the vast inland ice. Greenland is the world's largest island, covering area more than three times the size of Texas. Some 81 percent of it is covered by ice, and there are many glaciers. Glaciers are like slow-moving rivers of ice. Where a glacier meets the sea, its weight keeps it firmly resting on the bottom. A glacier's front is the point where the water is deep enough that the glacier floats. Since the 1970s, the front of Helheim stayed in the same place. Then it began melting rapidly, moving back 4.5 miles from 2001 through this past summer. It has also grown thinner, from top to bottom, by more than 130 feet since 2001. And over these past years, its trip to the sea has sped up from about 70 feet per day to nearly 110. The melting is driven by a warmer climate. Temperatures in Greenland have risen more than five degrees Fahrenheit  in the last ten years. Since most of Greenland's ice is on land, seas will rise as the ice melts. If all Greenland's ice sheet melted, oceans would be 15-20 feet higher. Nobody expects that to happen any time soon. According to the passage, we know that Greenland    _   .
belongs to Canada is the largest island in North America is all covered with glaciers is sinking under the sea level