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Phillips Station-Mountain Snowpack-Climate Change-DWR Snow Survey

New Study Identifies Mountain Snowpack Most “At-Risk” from Climate Change

As the planet warms, scientists expect that mountain snowpack should melt progressively earlier in the year. However, observations in the U.S. show that as temperatures have risen, snowpack melt is relatively unaffected in some regions while others can experience snowpack melt a month earlier in the year.

This discrepancy in the timing of snowpack disappearance—the date in the spring when all the winter snow has melted—is the focus of new research by scientists at Scripps Institution of Oceanography at the University of California San Diego.

In a new study published March 1 in the journal Nature Climate ChangeScripps Oceanography climate scientists Amato Evan and Ian Eisenman identify regional variations in snowpack melt as temperatures increase, and they present a theory that explains which mountain snowpacks worldwide are most “at-risk” from climate change. The study was funded by NOAA’s Climate Program Office.

Mountain snowpack changing rapidly in coastal regions

Looking at nearly four decades of observations in the Western U.S., the researchers found that as temperatures rise, the timing of snowpack disappearance is changing most rapidly in coastal regions and the south, with smaller changes in the northern interior of the country. This means that snowpack in the Sierra Nevada, the Cascades, and the mountains of southern Arizona is much more vulnerable to rising temperatures than snowpack found in places like the Rockies or the mountains of Utah.

The scientists used these historical observations to create a new model for understanding why the timing of snowpack disappearance differs widely across mountain regions. They theorize that changes in the amount of time that snow can accumulate and the amount of time the surface is covered with snow during the year are the critical reasons why some regions are more vulnerable to snowpack melt than others.

Mountain Snowpack-Climate Change-Scripps Institution of Oceanography

Using a new model, the Scripps researchers theorize that snowpack in coastal regions, the Arctic, and the Western U.S. may be among the most at-risk for premature melt from rising temperatures. Graphic: Courtesy Scripps Institution of Oceanography

Snowpack vulnerable due to increasing temperature

“Global warming isn’t affecting everywhere the same. As you get closer to the ocean or further south in the U.S., the snowpack is more vulnerable, or more at-risk, due to increasing temperature, whereas in the interior of the continent, the snowpack seems much more impervious, or resilient to rising temperatures,” said Evan, lead author of the study. “Our theory tells us why that’s happening, and it’s basically showing that spring is coming a lot earlier in the year if you’re in Oregon, California, Washington, and down south, but not if you’re in Colorado or Utah.”

Applying this theory globally, the researchers found that increasing temperatures would affect the timing of snowpack melt most prominently in the Arctic, the Alps of Europe, and the southern region of South America, with much smaller changes in the northern interiors of Europe and Asia, including the central region of Russia.

Climate Change and snowmelt

To devise the model that led to these findings, Evan and Eisenman analyzed daily snowpack measurements from nearly 400 sites across the Western U.S managed by the Natural Resources Conservation Service Snowpack Telemetry (SNOTEL) network. They looked at SNOTEL data each year from 1982 to 2018 and focused on changes in the date of snowpack disappearance in the spring. They also examined data from the North American Regional Reanalysis (NARR) showing the daily mean surface air temperature and precipitation over the same years for each of these stations.

Using an approach based on physics and mathematics, the model simulates the timing of snowpack accumulation and snowpack melting as a function of temperature. The scientists could then use the model to solve for the key factor that was causing the differences in snowpack warming: time. Specifically, they looked at the amount of time snow can accumulate and the amount of time the surface is covered with snow.

“I was excited by the simplicity of the explanation that we ultimately arrived at,” said Eisenman. “Our theoretical model provides a mechanism to explain why the observed snowmelt dates change so much more at some locations than at others, and it also predicts how snowmelt dates will change in the future under further warming.”

A “shrinking winter” and longer fire season

The model shows that regions with very large swings in temperature between the winter and summer are less susceptible to warming than those where the change in temperature from winter to summer is smaller. The model also shows that regions where the annual mean temperature is closest to 0˚C are less susceptible to early melt. The most susceptible regions are ones where the differences between wintertime and summertime temperatures are small, and where the average temperature is either far above, or even far below 0˚C.

For example, in an interior mountain region of the U.S. like the Colorado Rockies, where the temperature dips below 0°C for about half the year, an increase of 1°C can lead to a quicker melt by a couple of days—not a huge difference.

However, in a coastal region like the Pacific Northwest, the influence of the ocean and thermal regulation helps keep the winter temperatures a bit warmer, meaning there are fewer days below 0°C in which snow can accumulate. The researchers hypothesize that in the region’s Cascade Mountains, a 1°C increase in temperature could result in the snow melting about a month earlier in the season—a dramatic difference.

Arctic “at risk”

One of the most “at-risk” regions is the Arctic, where snow accumulates for nine months each year and takes about three months to melt. The model suggests that 1°C warming there would result in a faster melt by about a week—a significant period of time for one of the fastest warming places on Earth.

This study builds upon previous work done by Scripps scientists since the mid-1990s to map out changes in snowmelt timing and snowpacks across the Western U.S. The authors said that a “shrinking” winter—one that is shorter, warmer, and with less overall precipitation—has adverse societal effects because it contributes to a longer fire season. This could have devastating impacts on already fire-prone regions. In California, faster snowpack melt rates have already made forest management more difficult and provided prime conditions for invasive species like the bark beetle to thrive.

Funding for this work was provided by a NOAA/CPO grant to the University of California.

Current Steering Weather Hits Slowest Speed in 1,000 Years

An enormous ocean current that flows between continents in a worldwide circuit that can take centuries to complete is slowing down, scientists say. And climate change may be partly to blame.

New research finds that the Atlantic Meridional Overturning Circulation, or AMOC — a major ocean system that ferries water and heat between the equator and the poles — is at its weakest point in more than a thousand years.

Something was Killing Baby Salmon. Scientists Traced it to a Food-Web Mystery

The biologists working in a fish hatchery near Shasta Dam grew increasingly concerned last year when newly hatched salmon fry began to act strangely — swimming around and around, in tight, corkscrewing motions, before spiraling to their deaths at the bottom of the tanks.

Certain runs of chinook salmon in California are imperiled; the hatcheries and the fry raised there are the federal government’s last-ditch effort to sustain these ecologically and economically vital fish populations.

UCSD Gets $39 Million Grant for Renewable Energy Testbed

UC San Diego will receive a $39 million grant to build a testbed to allow universities, utilities and industry leaders to gain a better understanding of how to integrate renewable energy resources into the power grid, it was announced Monday.

California Could Do Better to Ease the Burdens of Wildfires If We Knew How Much They Actually Cost

Amid a record-breaking fire year, a new report out Thursday says the state lacks a grasp on the true costs of wildfires. The report is from the California Council on Science and Technology, an independent nonprofit organization established to offer state leaders objective advice from scientists and research institutions.

A New Kind of College Exam: UCSD is Testing Sewage for COVID-19

Turds tell tales, and UC San Diego is listening.

As the beginning of the school year nears, the university is preparing to ramp up its testing of sewage for the coronavirus. The goal: Monitor the progress of the pandemic on campus and catch outbreaks before it’s too late to control them. Along those lines, UCSD on Saturday sent out its first campus-wide email alert about the detection of the virus in sewage from one of its seven colleges.

Looking to Reopen, Colleges Become Labs for Coronavirus Tests and Tracking Apps

Thousands of students returning to the Rochester Institute of Technology in New York this month are being asked to wear masks in public, register their health status online each day and electronically log classroom visits for contact tracing if a coronavirus outbreak occurs. But the most novel effort at the school to measure and limit virus spread will require little effort and come quite naturally.

Students need only use the bathroom.

At more than 15 dormitories and on-campus apartment buildings, sewage is being tested twice weekly for genetic evidence of virus shed in feces. This provides a kind of early-warning system of an outbreak, limiting the need to test every student for Covid-19. If the disease is found in sewage, individual tests can be administered to identify the source.

A Quick, Cost-Effective Method to Track the Spread of COVID-19 Through Untreated Wastewater

A group of researchers have demonstrated that, from seven methods commonly used to test for viruses in untreated wastewater, an adsorption-extraction technique can most efficiently detect SARS-CoV-2. This gives us another tool to detect the presence and spread of the COVID-19 pandemic.

How LA’s Sewers Could Be an Early Warning System for Coronavirus Outbreaks

A study at USC is relying on the flush of a toilet for clues to coronavirus outbreaks.

Dr. Adam Smith, associate professor of civil and environmental engineering at USC, is a part of a team of scientists across the country who are sifting through data from the bowels of the sewer system.  The team consists of researchers from USC, Howard University, North Carolina State University and Rice University.

Groundbreaking Study: Earth Will Warm 4.9 to 7 Degrees F

How much warming will greenhouse gas emissions cause in the coming years? It’s one of the most fundamental questions about climate change — and also one of the trickiest to answer.

Now, a major study claims to have narrowed down the range of possible estimates.

It presents both good and bad news. The worst-case climate scenarios may be somewhat less likely than previous studies suggested. But the best-case climate scenarios — those assuming the least amount of warming — are almost certainly not going to happen.

It’s “the most important climate science paper that’s come out in several years,” according to climate scientist Andrew Dessler of Texas A&M University, who was not involved with the study.