Six months ago, climate science experts reported that it was the first time in 75 years Sierra Nevada meadow had no traces of snow. But now experts say that the situation may be more dramatic since the area’s snowpack is the lowest in more than five centuries.
According to a study published September 14 in the journal Nature Climate Change, Sierra Nevada snowpack has hit the lowest levels in over 500 years.
Valerie Trouet, lead author of the study and climate scientist at the University of Arizona, said that researchers had expected this year to be “extreme, but not like this.”
The recent research was an effort to gain a deeper insight into California’s 4-year-long drought and its historical causes. Past studies that had focused on a historical approach to the situation made use of tree rings to estimate past temperatures, droughts, and amount of rainfall in the area. But the recent study is the first to focus on the area’s snowpack.
Researchers explained that snowpack plays a huge role in replenishing California’s freshwater reservoirs every year. Moreover, Sierra Nevada snow accounts for nearly one-third of the state’s water.
First official records of the snowpack there began in the 1930s. Today there are more than 100 measuring stations scattered across the Sierra Nevada. According to the data gathered by those stations, the snow-water equivalent this year was just five percent of average since official records started.
But Trouet and her fellow scientists planned to dig deeper. They compared the data gathered by measuring stations and compared them with tree-ring information dating back to 1,400 A.D. Data on 1,500 blue oak trees, some of which were 1,400 years old, showed the amount of annual rainfall in the area, while data on different types of trees revealed how past temperatures fluctuated.
Trouet explained that rainfall is directly influenced by two factors – precipitation and temperatures. The higher the temperatures when precipitation falls are, the higher the odds precipitation would come down as rainfall rather than snowfall.
During their study, University of Arizona researchers learned that that the odds of such a “snow drought” to occur in Sierra Nevada more than once in half of millennium were less than five percent.
On the other hand, the return period in higher areas of Sierra Nevada where winter temperatures often reach freezing point was 95 years. The research team noted that precipitation in the area fell within the limits of natural variability. But as global temperatures continue to rise, the return period may become even shorter.
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