Accelerated Utah snowmelt possibly caused by diminishing Great Salt Lake's dust

Utah’s trademarked “greatest snow on earth” may be getting dirtier — and melting faster — due in part to dust blowing off newly exposed lakebed from the shrinking Great Salt Lake.

Snow in the Wasatch Mountains above Salt Lake City had more dust deposited on it in 2022 than in any year since observations began in 2009, researchers report in the June Environmental Research Letters. The dust accumulation caused snow to disappear 17 days earlier than if the snow had been clean.

An earlier, faster snowmelt may alter the water supply for the 1.2 million people who live in the region, as well as ecosystems downstream, says McKenzie Skiles, a snow hydrologist at the University of Utah in Salt Lake City. It also affects the region’s ski areas, which contribute more than $1.5 billion per year to the local economy.

In arid parts of the western United States, snow acts as a natural reservoir. More than half the municipal water in Salt Lake City comes from four streams that drain snow out of the Wasatch Mountains. But current forecasting tools don’t account for the impact of dust, Skiles says, which absorbs sunlight, speeding up snowmelt. That means people can’t accurately predict when snow runoff will happen so they can use water efficiently.

As an avid skier, Skiles noticed the slopes near Salt Lake City looked especially dirty in 2022. So she and colleagues investigated whether the increase in dust was related to consecutive years of record-low water in the Great Salt Lake (SN: 4/17/23).

The team collected snow samples from a plot adjacent to Alta Ski Resort and found that storms deposited substantial amounts of dust 16 times during the 2022 snowmelt season. After calculating where the dust came from during each storm based on wind direction and atmospheric conditions, the team found that Great Salt Lake contributed nearly a quarter of the total dust to the study site. It also released the most dust relative to the lake’s exposed surface area. This was surprising, Skiles says, because the Great Salt Lake’s dry lakebed is tiny compared with the exposed surfaces of neighboring dust sources, such as the much bigger West Desert, a dry landscape west of Great Salt Lake. The West Desert contributed about half of the dust, while other dried-up lakebeds and deserts, some as far away as Idaho and Nevada, delivered the rest.

“The future of Utah is going to be drier,” says Patrick Belmont, a hydrologist at Utah State University in Logan who was not part of the study. Earlier snowmelt causes the landscape to dry out faster, creating “a feedback loop that’s hard to break out of,” he explains. As Great Salt Lake shrinks and deposits more dust on the mountains, there’s less water available to refill the lake during the summer, which in turn exposes a larger dust source as the shoreline recedes.

A smaller lake also means less winter snow, Belmont says, as evaporation from Great Salt Lake contributes up to 10 percent of the snowpack in the Wasatch range. “Unless we make some big policy changes, we should expect to see a much lower Great Salt Lake, and it’s very possible that we lose the lake altogether.”

Skiles and her colleagues plan to keep monitoring the snowpack and to use remote sensing to see if dust is impacting snow across all of the mountains that drain into the Great Salt Lake. “We need more years of data to understand if this is the new normal,” she says.

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