In a megadrought like the one California is experiencing, people tend to look at how much rainfall has come along.
But it also matters when the snowmelt releases its cache, because the snowpack is the state’s natural reservoir.
“If you just change when the snow melts, it has huge consequences for the year,” said researcher Joseph Blankinship, a former UC Merced postdoctoral researcher who just published a paper in the journal Water Resources Research with UC Merced professor Stephen Hart based on their Sierra snow research. “There are definite climate-change implications.”
The hydrology journal is one of the most influential in the field, a further testament to the far-reaching research being conducted at UC Merced.
Hart, with the School of Natural Sciences and the Sierra Nevada Research Institute, and Blankinship, along with students, worked for three years, hauling bags of black sand into the mountains to artificially melt snow earlier than usual, mimicking the way the snowpack has been giving off liquid earlier and earlier every year. Right now, the snowmelt comes two to three weeks earlier than usual, but by the end of the century, it’s predicted to melt off two months earlier than normal.
The work will produce a series of papers, the first of which is “Snowmelt Timing Alters Shallow but Not Deep Soil Moisture in the Sierra Nevada.”
Early snowmelt means drying of surface soils earlier in the year, potentially slowing tree growth and the activity of soil organisms. Lower activity of the soil biota can also indirectly slow plant growth by reducing the soil supply of the growth-limiting nutrient nitrogen.
“We definitely expected the result of earlier drying, but we were surprised to find out it was more at the surface and not in the deeper soils,” Blankinship said. “We were also surprised to learn that the effects lasted throughout the dry season.”
The researchers experimented with different techniques to simulate realistic shifts in the timing of snowmelt, finally settling on the black sand, which absorbs the Sun’s warmth to passively melt the snow. One result of the experiment is that the technique proved more effective and realistic than others, and can potentially be used anywhere.
“This is an important predictive tool,” Blankinship said of the experiment. “One of our ultimate goals is to inform computer models. We want to help make better predictions of how climate change will impact important ecosystem services in the future.”
This experiment, which took place on plots of land 150 feet square, could be expanded to a larger area that has different plants and large trees to see whether they have similar effects on water and nutrient availability.
Hart wants to take the experiments further, delving into how the earlier snowmelt affects soil biota, nitrogen cycling and the various plants, and to work with other professors with other specialties to examine how drought — and its accompanying dust — affects snowmelt.