Spring Heat Waves Accelerating Snowmelt: A New Study Explores the Phenomenon
Recent research highlights a significant climatic phenomenon affecting snowmelt rates during spring. Dubbed “snow-eater heat waves,” these events can nearly double the usual rate at which snowpack melts, according to a study published in Science Advances.
Typically, snow melts at approximately 9 millimeters of water per day from March to July. However, during these heat waves, the rate skyrockets to about 17 millimeters per day. “There was basically a doubling of the rate of snowmelt during those days, compared to other days,” stated Dan McEvoy, a researcher with the Desert Research Institute in Reno and a co-author of the study.
Not every warm spring day qualifies as a snow-eater heat wave. Researchers identified these events by persistent temperatures at least 6 degrees Celsius above normal for three or more days, with overnight temperatures remaining above freezing. This lack of nighttime refreezing causes the snowpack to “ripen,” making it prone to rapid melting.
The study, involving Lawrence Berkeley National Laboratory and other institutions, notes that these heat waves are not only becoming more frequent but also occurring earlier in the year.
Since 1850, the area affected by these heat waves has expanded by approximately 102,000 square kilometers per century. Additionally, they are appearing about a month earlier compared to the mid-1800s. The Mountain West, since the 1950s, typically experiences three to five of these events annually.
A notable instance was the 1983 Memorial Day heat wave, which caused flooding along Utah’s Wasatch Front and led Salt Lake City to construct emergency canals.
McEvoy emphasized the challenges these rapid melts pose for water resource management. Reservoirs are designed for gradual snowmelt, and the swift influx of water increases the risk of flooding if snowpack levels are high. “Is there room in the reservoir? They’re used to it more slowly coming down the system,” McEvoy noted. “And that rapid melt has a much higher potential to cause flooding if there’s enough snow left.”
Even during dry years, snow-eater heat waves can be problematic. They do not introduce additional water into the ecosystem but rather accelerate the melting of existing snowpack, potentially depleting water resources needed later in the summer. The study highlights that significant snow-eater events have occurred during major Western snow droughts, such as California’s drought from 2013 to 2015.
