When Paul Gowen, 83, saw turquoise-green water spilling into the Frederick Sound and Wrangell Narrows in Alaska at the end of last month, he knew a glacier lake on the Baird Glacier had burst. Further up the Frederick Sound, residents noticed a larger quantity of icebergs and stronger currents.

“This is amazing, this turquoise color as far as we can see on Frederick Sound,” he told the local radio station, K-FSK, at the time. “It’s very unusual to have this much outwash of color.”

Outburst floods on glaciers are not uncommon — water accumulates within the ice or in dips, but eventually breaks through the ice barrier holding it in. The turquoise-green colour of the water comes from sediments that tend to accumulate in glacier lakes, often called glacial flour or milk. Climate change is expected to increase the risk of Glacial Lake Outburst Flooding as glacier melt accelerates, according to the World Wildlife Fund.

The last time a lake burst on the Baird Glacier was 1991, though the event was much smaller. Between 2000 and 2009, the glacier had lost 10 to 20 metres of thickness. Later, glaciologist Mauri Pelto reported in 2013 that two large lakes 400-600 metres were expanding.

Closer investigation from the U.S. Forest Service in the area found that the most recent September flood likely originated in the Witches Cauldron branch of the glacier.

“There’s no water,” Jim Baichtal, Geologist for the U.S. Forest Service said. “It’s all gone and it looks like there’s been a tremendous amount of collapse of the surface of the ice.”

The glacier’s surface has new crevasses, sinkholes, and fractures. According to Baichtal, the surface may have sunk 50 or 60 feet after the flood.

Government officials will have to keep an eye on the glacier, as it will be hard to predict whether another flood is likely.

“You can really have a situation where a place essentially gets safer in terms of natural hazards or you can have the opposite,” said Martin Truffer, a glaciologist at the University of Alaska.