* Normal melt ponds prompt questions about global warming
* "Just part of summer ice conditions," oceanographer says
By Environment Correspondent Deborah Zabarenko
WASHINGTON, July 29 (Reuters) - Images of a scientific observation buoy floating in what appeared to be an Arctic lake near the North Pole lit up the online world in the past week, sparking questions about whether this was a sign of global warming.
On Monday, the scientist who installed the buoy gave a succinct answer: No.
Also, the buoy was never quite at the North Pole, oceanographer James Morison said in a telephone interview. Its most recent location is about 300 miles (480 km) away.
After about a week of being surrounded by water, the buoy sat on top of a frozen sea on Monday, just as it had earlier this summer. Current images are visible at http://psc.apl.washington.edu/northpole/NPEO2013/webcams1and2.html .
The water the buoy was bobbing in last week was not a lake, but a melt pond, a common occurrence in the Arctic summer when the sun shines 24 hours a day, said Morison, principal oceanographer for the North Pole Environmental Observatory, funded by the U.S. National Science Foundation.
While the air temperature hovers right around the freezing point, solar radiation works to melt snow and the upper layer of sea ice. Some of the water drains through cracks down into the Arctic Ocean and the rest forms fresh-water ponds on top of the sea ice with their surfaces slightly above sea level.
"That's just part of summer ice conditions, and as far as we know it always has been," Morison said.
Morison said he experienced melt ponds when he stayed in an Arctic ice camp.
FROM MUKLUKS TO HIP-WADERS
"Melt ponds become part of your life," he said. "They build little plywood bridges over the melt ponds, your footwear changes completely from giant sock-like mukluks to hip-waders and it's really miserable."
This particular pond grew roughly to about the size of an Olympic swimming pool, with a width of up to 55 yards (50 metres), and a depth of perhaps 2 feet (60 cm). Below the pond was a layer of ice more than 3 feet (1 metre) thick, Morison said from the Applied Physics Laboratory at the University of Washington in Seattle.
Morison and his team installed the scientific observing buoy in April, about 25 miles (40 km) from the North Pole. The buoy did what it was supposed to do, drifting with the Arctic sea ice to help scientists track what the ice was doing. By last week, the buoy was 300 miles (480 km) from the pole, he said.
Another scientific observing buoy is currently about 60 to 100 miles (100 to 160 km) to the north of this one, but that buoy did not have a webcam trained on it.
The webcam archives show that from July 20 to 21, the buoy went from having a few big pieces of ice around it to being completely surrounded by water. On Sunday, the buoy went from floating to sitting atop a skin of sea ice. By Monday there was ice and snow around it.
Last year, Arctic sea ice cover dropped to its lowest summer level, according to the U.S. National Snow and Ice Data Center. Morison and his colleagues voiced concern in a statement about warm Arctic winter air temperatures that inhibit ice growth, and heat in the ocean that would melt the under-surface of sea ice. (Reporting by Deborah Zabarenko; Editing by Ros Krasny and Mohammad Zargham)