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Snowmobilers who enjoy cruising the groomed roads inside Yellowstone National Park might want to pick up a new winter hobby in the coming decades.

New research on declining snowpack levels in Yellowstone predicts significantly fewer days that snowmobiles and snowcoaches will be able to travel on some of the park’s most popular routes. By the end of the century, the road from West Yellowstone might not be rideable at all, though a few high-elevation routes figure to remain open most winters.

The peer-reviewed study was published July 28 in the online journal PLOS One. The authors, Mike Tercek and Ann Rodman, used climate models and historic data from Snotel climate sensor sites positioned near roads in the park to forecast snowpack levels through 2090.

Tercek, a Gardiner-based ecologist, said research has shown that average snowpack levels in Yellowstone have already declined precipitously in recent years. And it’s only going to get worse as the climate continues to warm, he said.

Yellowstone’s winter recreation season runs December to March and brings in $60 million annually in tourism revenue to gateway communities. When there were poor snow conditions in Yellowstone in recent winters, Tercek said people often said, “Oh, this is just a bad year, but it’ll be OK next year.

“But this isn’t just an isolated incident when you have a bad year,” he said in a Wednesday interview. “What we consider to be a bad year now is going to be average in the future.”

Under a climate change scenario where greenhouse gas emissions remain at current levels, the season for snowmobilers would be shortened by 13 percent on average between 2030 and 2060, and 16 percent between 2060 and 2090, the study said.

Under a scenario that predicts emissions continuing to go up at their current rate, however, the winter recreation season would on average be shortened by 16 percent in the mid-century time frame, and 26 percent late in the century, the researchers said.

The least amount of snow the researchers considered rideable by snowmobiles was 4 inches of “snow-water equivalent” — or roughly 12 inches of snow coating the road.

Some snowmobile routes will be in worse shape than others. The study said the lower-elevation West Entrance road, adjacent to West Yellowstone, will only be rideable about half the winter season by mid-century. Later in the century, it may be open as little as 29 percent of the time.

But the high-elevation South Entrance route, accessed from Jackson, Wyo., will likely continue to remain open to snowmobile traffic most years, as it is colder and receives more snowfall than other areas of the park.

“Where we have the deepest snow now, those are the areas that will be pretty good in the future,” Tercek said. “There’s more snow to lose, essentially.”

The researchers focused on average snowpack levels over the two 30-year time frames. But Tercek noted that some individual years will be far worse than others. There could be back-to-back years where lower-elevation snowmobile routes aren’t rideable all winter, he said, because there is too much pavement exposed.

Traditional metal ski snowmobiles are likely to “become increasingly ill-adapted to the conditions that prevail on Yellowstone’s roads in the winter,” the study said.

One solution officials already are experimenting with is converting snowcoaches to use large, low-pressure tires instead of tracks so that they can cross both snow and pavement. But snowmobiles might not be so adaptable, Tercek said.

Patchy snow also might mean some park roads will open up to cars in the winter, perhaps pushing snowmobile and snowcoach staging areas farther inside the park, Tercek said.

“It’s something we’re going to have to adapt to,” he said.

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