Matthew LaPlante doesn\u2019t have to go to a lab to see his research in action. On some mornings, he can just look out his own window in the mountains high above Salt Lake City. After a warm night when the temperature stays above freezing, he\u2019ll wake up and see that the snow level has dropped by inches, revealing more of the aspens he taps for syrup.<\/p>\n
\u201cIt feels like a monster came and just in the middle of the night, took a bite out of a snowpack,\u201d said LaPlante, a journalist and climate scientist at Utah State University.<\/p>\n
So it\u2019s fitting that scientists have started calling these kinds of heat waves, marked by unusually high temperatures in the spring and early summer, \u201csnow eaters.\u201d\u00a0LaPlante was part of a recent study, published in the journal Science Advances, that attempted, for the first time, to identify what conditions exactly make for a \u201csnow eater.\u201d Compared to normal warm spells or heat waves, the researchers determined that these events happen when temperatures stay above freezing through both day and night for multiple days, typically three to five. These events can roughly double the rate at which snow melts, causing flooding and making it challenging to manage water resources.\u00a0<\/p>\n
\u201cSnow eaters\u201d appear to be occurring earlier in the year and becoming more widespread in the Western United States as the climate warms. Since the 1850s, the study found, the area affected by snow eaters has increased by an average of about 40,000 square miles per century, and the first snow eater of the season has been arriving about one month earlier per century.\u00a0<\/p>\n
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The term \u201csnow eater\u201d has a murky history. By at least the 1880s, people in the West were talking about \u201csnow-eating\u201d chinooks, warm mountain winds that make snow disappear quickly. More recently, the phrase \u201csnow-eater heat wave\u201d first made headlines in March, when an early heat wave enveloped much of the West, quickly wiping away snowpack in the Colorado Rockies and California\u2019s Sierra Nevada. The scientists hope the catchy, evocative term can help draw more attention to this type of heat wave, since there\u2019s still a lot to learn. The study only looked at the Western U.S., but snow eater heat waves almost assuredly occur elsewhere, LaPlante said.<\/p>\n
Solar radiation is a major, but sometimes overlooked, driver of snowmelt, said Noah Molotch, a professor of geography at the University of Colorado Boulder who was not involved in the new study. When it interacts with heat waves, those impacts are amplified. As snow crystals warm up, they lose some of their structure and light-reflecting abilities, causing snowpacks to absorb more sunlight and melt faster. \u201cIt\u2019s a little bit of a \u2014 no pun intended \u2014 a snowball effect,\u201d he said.<\/p>\n
Much of the Western U.S. saw record-low snowpack this spring. What was really unusual about it, Molotch said, was how widespread it was. Colorado received less precipitation than normal this winter, while California got lots of precipitation, but in the form of rain instead of snow. But across the region, \u201cthe one thing in common was above-average air temperatures,\u201d Molotch said.<\/p>\n
These conditions have likely helped fuel exceptionally severe wildfires in the West, from Utah to Spokane, Washington, where hundreds of homes burned earlier this month. \u201cDrought stress for mountain forests around the Western U.S. is heavily dictated by the snow that accumulates each winter and then melts through the spring and summer,\u201d Molotch said. \u201cThere is a direct connection there in terms of the water availability and drought stress that can provide one of the important ingredients for increases in wildfire intensity and frequency.\u201d<\/p>\n
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If scientists are able to better predict what will happen to snowpack, it could help water managers plan for what\u2019s coming. Early or rapid snowmelt poses problems for managing water resources in the West, where snowpack serves as a key source of fresh water in the drier summer months. \u201cWater that would otherwise be stored as snow comes out early, and then we have to deal with it as a hazard instead of a resource at our reservoirs and along the rivers and streams,\u201d said Ben Hatchett, a co-author on the study and a scientist at Colorado State University\u2019s Cooperative Institute for Research in the Atmosphere.<\/p>\n
Snow-eater heat waves also may pose risks to skiers, hikers, and anyone else on or near mountains. They could be linked to hazards such as avalanches, glacial collapses, and permafrost melt, Hatchett said, though scientists are still investigating those connections. He lives in the Sierra Nevada, and he\u2019s noticed one tangible change over his lifetime: The soundscape has changed.<\/p>\n
\u201cAt night, it used to be quiet,\u201d he said. \u201cAnd now it\u2019s not quiet, because everything\u2019s melting all the time.\u201d<\/p>\n
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