EcoWatch: NASA scientists are worried about Greenland. Its ice sheet is three times the size of Texas and a mile deep on average. The only place with more of the worlds ice is Antarctica. But Greenland is warming twice as fast as Antarctica, NASA says. This rapid melting is raising global sea levels at an alarming rateeven faster than expected. Thats why NASA scientists are monitoring Greenlands ice sheet from high up in space to the ocean floor below to provide data for scientists studying the global...