Sierra peaks grew an inch during drought
California’s already towering Sierra Nevada summits rose to new heights during the drought, albeit by just a hair.
A study by NASA scientists published Wednesday found that the granite peaks of the 400-mile range were pushed nearly an inch upward between 2011 and 2015, a phenomenon linked not only to known tectonic forces but the expansion of the land as it dried out and shed water weight.
The findings suggest that a lot more water lies deep inside the rock of the Sierra than previously thought. The water is sneaking in and out through cracks in the ground, enough so that even the elevation of the biggest mountains are changing — including the lower 48 states’ tallest peak.
“Yeah, you could say Mount Whitney is at its highest,” said research scientist Donald Argus of NASA’s Jet Propulsion Laboratory in Pasadena, who led the study. “Although it’s only a little bit higher, of course.”
Previous studies have noted the Sierra’s uplift, a process that’s been hoisting the range for millions of years. But none has recognized such a large contribution from water loss.
Other studies have shown that the floor of the Central Valley sank rapidly during the historic drought, with nearly 2 inches lost in the worst months in some places as desperate farmers pumped out the groundwater beneath them.
California’s reputation as a state of extremes may be more true than ever.
The NASA team found that the rebounding of the mountains as water moved out accounted for 71 percent of the Sierra’s 0.94-inch rise during the height of the drought between October 2011 and October 2015.
About 8 percent of the rise was due to the longtime geological uplift that gave birth to the mountains. Roughly 21 percent was the result of groundwater pumping in the nearby Central Valley, where the aquifers have become so devoid of water that their weight has stopped dragging down the Sierra.
The mountains also rise and fall seasonally ever so slightly. Snow and rain tend to weigh down the ground surface in winter and spring, while meltoff and evaporation ease the burden in summer and fall. The NASA study, published in the Journal of Geophysical Research: Solid Earth, accounted for this cyclical fluctuation.
The research data came from 1,300 sensors laid out across the mountains that can detect the smallest of elevation shifts, to less than a tenth of an inch.
The scientists calculated that the loss of 10.8 cubic miles of water helped lift the Sierra during the drought’s four peak years. That’s about 45 times what the city of Los Angeles uses in a year.
The group did not pinpoint where the water was coming from, identifying it only as being deep in the soil and recesses beneath the rock. They noted that this source could not be tapped for human use.
Since the drought began winding down two years ago and more rain and snow has hit the Sierra, the mountains’ core has started to refill with water. As a result, scientists said, the range has also begun to fall.