Last year’s record-low snowpack levels were caused by high temperatures produced by both greenhouse gases and, in some areas, a recently discovered enormous patch of warm water in the northern Pacific Ocean, dubbed the blob, UCLA researchers said Monday.
In 1977, which was the last year of major snow drought, the low snowpack levels were attributed primarily to lack of precipitation.
“The story in 2015 was really the exceptional warmth,” said UCLA geography professor Dennis Lettenmaier, one of the authors of the study published in the journal Geophysical Research Letters.
“Historically, droughts in the West have mostly been associated with dry winters, and only secondarily with warmth,” Lettenmaier said. “But 2015 was different, especially in California, but in Oregon and Washington, as well, the primary driver of the record low snowpacks was the warm winter.”
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Last year, more than 80 percent of sites measured in the westernmost region of the United States experienced record-low snowpacks, which feed streams and rivers as they melt, providing crucial water supply.
California has been in a drought since 2011 and this multi-year period of low precipitation, by some measures, is the state’s most severe in 500 years. In 2015, higher temperatures combined with low precipitation, leading to one of the lowest snowpack levels on record.
Oregon and Washington, on the other hand, also experienced much higher- than-average temperatures during the last two years but were not as dry as California. Oregon, in fact, was 6.5 degrees warmer than average during that period.
“The 2015 snowpack season was an extreme year,” said Philip Mote, director of the Oregon Climate Change Research Institute at Oregon State University and lead author on the study. “But because of the increasing influence of greenhouse gases, years like this may become commonplace over the next few decades.”
Higher sea surface temperatures led to a huge patch of warm water, known as the blob, which appeared in the northern Pacific Ocean more than two years ago, according to the study co-authored by professors from UCLA and Oregon State University.
Scientists aren’t sure why the blob formed, though many blame a ridge of high pressure that brought sunnier weather and less mixing of surface water with colder, deeper water.
“Some recent studies suggest that a high pressure ridge that caused warmer temperatures over land also created the blob, but our results suggest that the blob itself may also have contributed to the warm winter here,” Mote said.
–City News Service