Finding a Path with Help From Above
The Chinese research boat Xue Long met an immense, frozen wall last summer while picking its way through rafts of ice in the Arctic Ocean. Dense fog prevented the ship's captain from finding a route around the ice dam. The fog also grounded the ship's other navigational tool, a helicopter on deck. Feeling lost, the captain needed a guide through the maze. Help came from 500 miles above, where a Canadian satellite named Radarsat orbits Earth 14 times a day.
Radarsat, launched in 1995, can detect bumps and valleys on the ground through clouds, fog and darkness. Known as a synthetic aperture radar satellite, Radarsat sends out microwave pulses that penetrate clouds and darkness to sense differences in Earth's surface. The microwave pulses return to the satellite, which converts them to data bits and sends them to tracking stations on the ground. During the six-week expedition of the Xue Long, which marked the first time the Chinese explored the Arctic with an icebreaker, 40 researchers studied sea ice and set up a camp on the ice. Roger Colony of the International Arctic Research Center at the University of Alaska Fairbanks wrote a proposal in which the Chinese agreed to share what they learned in exchange for some technical support.
The Chinese were searching for climate change clues in an area recently studied by Americans and others, and every little bit of information helps. The Chinese scientists needed help when the Xue Long ran into a wall of sea ice, a common hazard of Arctic Ocean travel. During summer, the ice pack on top of the world covers about 6 million square kilometers. It isn't a solid cap; it's made of ice floes, acres of ice that look like a floating jigsaw puzzle. Ships like the Xue Long usually rely on the navigator's eyesight or an optical satellite for a path through the puzzle pieces, but foggy days can stop a ship cold. Radarsat got the Xue Long out of a jam by sending information down to the antenna dish on top of the Geophysical Institute, where technicians at the Alaska Synthetic Aperture Radar Facility transferred the data to the Canadian Ice Service in Ottawa. Workers there converted the bites of information into an ice map, which they routed to China's National Oceanic Bureau in Beijing. A staff member there faxed the ice map to the captain of the Xue Long. The map showed the ship as a tiny sliver of white blocked by miles and miles of sea ice. The captain decided the ice was too thick and turned the boat around. Later, he used the same map later to find his way back into the maze.
