Cooperative Institute for Research in Environmental Sciences

The annual hole in the Antarctic ozone layer could show initial signs of recovery within 10 years, according to a new analysis of 25 years of data collected by scientists from the Cooperative Institute for Research in Environmental Sciences (CIRES) and NOAA at the South Pole.

The scientists have long tracked ozone levels high in the Antarctic atmosphere with balloon-borne instruments, keeping an eye on the annual springtime opening and closing of the ozone hole.

The ozone layer protects Earth from some damaging incoming solar radiation; an ozone hole allows more incoming radiation to hit the surface, elevating the risk of skin cancer, crop damage, and other environmental impacts.

The research team – led by Birgit Hassler a scientist at CIRES and NOAA’s Earth System Research Laboratory in Boulder, Colo. – analyzed the rates at which springtime chemical reactions ate away the ozone above the South Pole during the last 25 years.

The team related those “ozone loss rates” to the atmosphere’s levels of ozone-depleting chemicals, which are declining in abundance because of the international Montreal Protocol agreement to protect the ozone layer.

Projecting that relationship into the future, the research team calculated that between 2017 and 2021, the South Pole data will show that ozone is not being lost as quickly during the spring – an early sign that the Antarctic ozone hole is healing.

The research was published online Thursday in the Journal of Geophysical Research.

WHAT: Availability of scientist to discuss ozone loss paper

WHO: Birgit Hassler, CIRES scientist, lead author

Karin Vergoth, CIRES, 303-497-5125,

While climate change will not modify the extent or frequency of El Niño variability in the next 100 years, the environmental consequences of such events may become more extreme, according to a new collaborative study between scientists at the Cooperative Institute for Research in Environmental Sciences (CIRES) and the National Center for Atmospheric Research (NCAR).

"Based on the latest state-of-the-art model, it does not appear that the warm water/cold water anomaly in the Pacific—known as El Niño and La Niña—is changing," said study coauthor Baylor Fox-Kemper, a CIRES Fellow and assistant professor at the Department of Atmospheric and Oceanic Sciences at the University of Colorado Boulder. "But due to a warmer and moister atmosphere the impacts of El Niño are changing even though El Niño itself doesn't change."

El Niño events—anomalous warming of the surface water of the eastern and central Pacific Ocean, occurring every four to 12 years—typically coincide with atmospheric changes like reduced trade winds and a displaced jet stream, which can cause unusual weather patterns such as flooding or droughts. These weather patterns can have dire consequences: "Tens of billions of dollars are associated with big El Niño events or La Niña events," Fox-Kemper said.

Advance knowledge of variations in El Niño behavior would allow a community to better prepare, for example, by altering planting seasons or water usage, Fox-Kemper said. "We would like to ask questions such as whether the flooding that occurred in Australia will happen more or less often over the next 100 years," he said. "If one of the impacts of climate change is a changing El Niño, we would like to know as soon as possible so we could start planning."

To determine whether El Niño may become stronger or more frequent in a warming climate, and whether the impacts of El Niño may change, the researchers used the most recent and advanced climate model available from NCAR—the latest version of the Community Climate System Model that scientists are using for the experiments that will inform the next Intergovernmental Panel on Climate Change (IPCC). They compared the model reproductions of variability in ocean surface temperature in the 20th century with model simulations that extended into the 21st century, and found that the changes were not significant. The study was published online in September in the Journal of Climate.

The impacts of El Niño, however, were affected by a warming climate, Fox-Kemper said. "What we see is that certain atmospheric patterns, such as the blocking high pressure south of Alaska typical of La Niña winters, strengthen in the model in the future climate as compared to the 20th century," he said. "So, the cooling of North America expected in a La Niña winter would be stronger in future climates."

Moreover, Fox-Kemper cautions that although El Niño does not appear to be changing in the short-term, it may change in the future under the influence of current climatic warming. Because the oceans heat up slowly and ocean currents move slowly there is a subsequent time lag before the tropics warm up. This means scientists will have to wait longer to see if there are any changes to El Niño with a changing climate, he said. "Even 100 years from now, ocean warming is still working its way through the system," he said. "This study isn't saying there isn't going to be a change to El Niño—it is just that the adjustment process is still happening."

The National Aeronautics and Space Administration, National Science Foundation, the US Department of Energy and the National Energy Research Scientific Computing Center provided funding for the study "Will there be a significant change to El Niño in the 21st century?" Lead author of the study is CIRES scientist Samantha Stevenson and coauthors on the study include NCAR researchers Markus Jochum, Richard Neale, Clara Deser and Gerald Meehl.

Baylor Fox-Kemper, CIRES, 303-492-0532,
Karin Vergoth, CIRES, 303-497-5125,

Wintertime droughts are increasingly common in the Mediterranean region, and human-caused climate change is partly the cause, according to a new analysis by scientists at the Cooperative Institute for Research in Environmental Sciences (CIRES) and colleagues at NOAA. In the lands surrounding the Mediterranean Sea, 10 of the driest 12 winters since 1902 have struck in just the last 20 years.

“The magnitude of drying that has occurred is too great to be explained by natural variability alone,” said Martin Hoerling of NOAA’s Earth System Research Laboratory in Boulder, Colo., lead author of a paper published online in the Journal of Climate Oct. 27, 2011. “This is not encouraging news for a region that already experiences water stress because it implies natural variability alone is unlikely to return the region’s climate to normal.”

Hoerling’s team uncovered a pattern of increasing wintertime dryness that stretched from Gibraltar to the Middle East. The scientists used observations and climate models to investigate several possible culprits including natural variability, a cyclical climate pattern called the North Atlantic Oscillation (NAO), and climate change caused by greenhouse gases released into the atmosphere during fossil fuel use and other human activities.

Climate change from greenhouse gases explained roughly half the increased dryness of 1902-2010, the team found. This means that other processes – none specifically identified in the new investigation – may also have contributed to increasing drought frequency in the region.

The team also found a surprising coincidence between the observed increase in winter droughts and in the projections of climate models that include known increases in greenhouse gases and aerosols. Both observations and model simulations show a sudden shift to drier conditions in the Mediterranean beginning in the 1970s.

The physical reasons for the relationship between climate change and Mediterranean drought involved sea surface temperatures, the researchers reported. In recent decades, greenhouse-induced climate change has caused somewhat greater warming of the tropical oceans than other ocean regions. That pattern has acted to drive drought-conducive weather patterns around the Mediterranean. The timing of the ocean change coincides closely with the timing of increased droughts, the scientists found.

The Mediterranean has long been identified as a “hot spot” for substantial impact from climate change in the latter decades of this century, because of water scarcity in the region and climate modeling that projects increased risk of drought.

“The question has been whether this projected drying has already begun to occur,” Hoerling said. “The answer is yes, in winter.”

Coauthors on the paper “On the Increased Frequency of Mediterranean Drought” are CIRES Fellow Judith Perlwitz and CIRES scientists Jon Eischeid, XiaoWei Quan,Tao Zhang, Philip Pegion.

Judith Perlwitz, CIRES, 303-497-4814, 
Katy Human, CIRES, 303-735-0196,

The sky glow that radiates from cities at night does more than obscure the stars—it also impacts daytime air pollution levels, according to new research from the Cooperative Institute for Research in Environmental Sciences (CIRES).

“This is the first time that this effect has been quantified,” said CIRES scientist Harald Stark, the lead author. “Previously, it was unknown if city lights could influence air pollution.” They do so by breaking down a compound called the nitrate radical that naturally helps cleanse the atmosphere. Acting as a “janitor” of the night sky, the nitrate radical scrubs away air pollutants such as volatile organic compounds that would otherwise form smog and ozone. The cleansing compound only works nightshifts, however, since sunlight destroys the light-sensitive molecule. But the new data reveal that urban lights in cities like Los Angeles are bright enough to also destroy the nitrate radical, decreasing levels by up to 4 percent in the skies over L.A.

The researchers report an encouraging finding, however. Although artificial lights break down the nitrate radical into nitrogen dioxide—an essential molecule for ozone production—it appears from model simulations that this has only a small effect on next-day levels of ozone, one of the major types of air pollutants. “One reason for this is that ozone doesn’t depend linearly on nitrogen compounds,” Stark said. “Other factors such as sunlight, volatile organic compounds and the amount of mixing between layers of the atmosphere also affect ozone production.” Another reason for the small effect could be that the model may have underestimated the impact of nitrate-radical loss on ozone production, Stark said. More detailed model calculations in the future could give more precise answers.

Still, “An important point to keep in mind is that even small changes in ozone levels may decide whether cities are below or above regulatory levels,” Stark said.
Stark and his team flew several nighttime flights over L.A. in May and June 2010, measuring light intensities and concentrations of nitrogen compounds and ozone. They presented some of the initial results at the 2010 American Geophysical Union Fall Meeting and published the full results of their study as a Correspondence article in the November 2011 issue of Nature Geoscience.

The study also assessed the likelihood of urban lights elsewhere in the world altering nitrogen chemistry. Cities such as Chicago, Las Vegas, Valencia, New York City and Tokyo are much brighter than L.A., and the researchers’ calculations show that their nighttime glare likely degrades the nitrate radical at a much higher rate than above L.A., with unknown consequences to air quality.

The data come on the heels of other research showing that light pollution carries other negative effects, such as harming human health by upsetting circadian rhythms, disrupting animal behavior and wasting energy and money for misdirected lighting that shines into the night sky. Methods for reducing light pollution include using shielded light fixtures that direct the light to the ground, rather than into the sky; and intelligent lights that only switch on when they are needed.

Stark and his team next plan to study other cities with brighter lights (such as Chicago) and more pollution (like Beijing) to quantify how much nitrate-radical loss affects air pollution in these locations. Such research could help inform decision makers on new and better ways to improve air quality.

NOAA Climate Change and NOAA Health of the Atmosphere provided funding for the study.

Harald Stark, 303-492-0840,

Karin Vergoth, CIRES,, 303-497-5125

The Green Data Center Team at the National Snow and Ice Data Center (NSIDC), part of the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder, has received the Colorado 2011 Governor's Award for High-Impact Research. The team was recognized for its innovative data center redesign that slashed energy consumption for data center cooling by more than 90%, demonstrating how other data centers and the technology industry can save energy and reduce carbon emissions.

The Green Data Center went online in summer 2011. The heart of the design includes new cooling technology that uses a fraction of the energy required by traditional air conditioning. The second phase of the project, to be completed in late 2011, includes an extensive rooftop solar array that will result in additional energy savings. The design team was led by NSIDC technical services manager David Gallaher, in collaboration with several Colorado-based companies and the National Renewable Energy Laboratory (NREL).

Researchers around the world who study Earth's snow, ice, and climate, access data from NSIDC's active data archive, a bank of computers and storage devices that require a cool environment to operate. The machines themselves generate heat. "Even in the dead of winter, our computer room air conditioners were cranking full tilt trying to chill off the 100-degree-plus heat coming off the back of these units," Gallaher said.

Just cooling NSIDC's computer room used to require over 300,000 kilowatt-hours of energy per year, enough to power 34 homes. "There was a certain irony that here we are working on climate research and our data center was consuming an awful lot of power," Gallaher said.

The Green Data Center design takes advantage of Boulder's arid climate. "We're using a new technology called indirect evaporative cooling," Gallaher said. These units, manufactured by Coolerado Corporation, cool by blowing air over water, using much less energy than compressors. Unlike traditional evaporative cooling, indirect evaporative cooling does not add humidity to the room, maintaining the dry environment that computers need.

Smart control technology also saves energy. During much of the year, the system cools the data center by pulling in and filtering outdoor air. On hot days, the new cooling units automatically step in. The solar array will normally feed energy back into the electrical grid, further reducing the center's net carbon footprint. In case of a power outage, the solar array will charge the batteries that provide NSIDC's emergency power supply.

"The technology works, and it shows that others can do this too," Gallaher said. "Data centers are big consumers of energy, and a lot of it is for cooling." According to the U.S. Environmental Protection Agency (EPA), as of 2006, U.S. data centers were estimated to consume 61 billion kilowat- hours of electricity, equivalent to the electricity consumed by 5.8 million average U.S. households. By 2020, the carbon footprint of data centers will exceed that of the airline industry.

NSIDC received a grant for the project from the National Science Foundation (NSF) under its Academic Research Infrastructure Program, with additional support from NASA. NSIDC, which is supported entirely by federal research funding, manages scientific data from NSF field programs and from NASA's Earth Observing System remote sensing program.

The Green Data Center was conceived when NSIDC faced an expensive replacement of its aging, ailing computer room air conditioners. The new evaporative cooling units not only save energy, but offer lower cost of maintenance.

The Governor's Award for High-Impact Research recognizes innovations by Colorado's federally sponsored science and technology laboratories that have made significant impacts beyond the labs. Colorado Governor John Hickenlooper will present the award during a reception at the LEEDS Platinum-certified Xcel Energy building in downtown Denver on November 15th.

The Green Data Center team includes David Gallaher, NSIDC Director Mark Serreze, and Ronald Weaver from NSIDC; Rick Osbaugh from RMH Group in Denver; Otto Van Geet from the National Renewable Energy Laboratory (NREL); and Lee Gillan from Coolerado Corporation.

For more information on NSIDC's Green Data Center, including a monitor of computing center energy usage and cooling, visit

NSIDC supports research into Earth's frozen regions, including sea ice, snow cover, glaciers, ice caps, ice sheets, permafrost, and climate interactions. NSIDC performs scientific research, manages and distributes scientific data, and educates the public. For more information, visit

The 2011 Governor's Award for High Impact Research is sponsored by CO-LABS.

CO-LABS Press Release

University of Colorado Boulder Press Release

Jane Beitler
National Snow and Ice Data Center
University of Colorado Boulder

Elizabeth Lock
University of Colorado Boulder
Media Relations

CIRES Director Konrad Steffen has been named a Fellow of the American Association for the Advancement of Science (AAAS).

Election as a AAAS Fellow is an honor bestowed upon AAAS members by their peers. This year AAAS has awarded 539 members this honor because of their scientifically or socially distinguished efforts to advance science or its applications. New Fellows will be presented with an official certificate and a gold and blue (representing science and engineering, respectively) rosette pin on Saturday, 18 February from 8 to 10 a.m. at the AAAS Fellows Forum during the 2012 AAAS Annual Meeting in Vancouver, B.C., Canada.

Former CIRES Fellow Pieter Tans, currently a senior scientist in NOAA's Climate Monitoring and Diagnostics Laboratory also received the honor. This year's AAAS Fellows will also be formally announced in the AAAS News and Notes section of the journal Science on 23 December 2011.

The amount of air pollutants in the atmospheric plume generated by the Deepwater Horizon oil spill was similar to those generated by a large city according to a new study led by scientists at the Cooperative Institute for Research in Environmental Sciences and NOAA.

The researchers focused on ozone and particulate matter—two pollutants with human health effects and published their results in a recent special issue of Proceedings of the National Academy of Sciences.

About eight percent, or about one of every 13 barrels of the Deepwater Horizon-spilled oil that reached the ocean surface, eventually made its way into airborne organic particles small enough to be inhaled into human lungs, and some of those particles likely reached the Gulf Coast when the winds were blowing toward the shore, according to the study.

"We could see the sooty black clouds from the burning oil, but there’s more to this than meets the eye. Our instruments detected a much more massive atmospheric plume of almost invisible small organic particles and pollutant gases downwind of the oil spill site," said Ann M. Middlebrook, scientist at NOAA ESRL’s Chemical Sciences Division (CSD) and lead author of the study.

According to the study, over the course of the spill, the total mass of organic particles formed from evaporating surface oil was about ten times bigger than the mass of soot from all the controlled burns. Controlled burns are used to reduce the size of surface oil slicks and minimize impacts of oil on sensitive shoreline ecosystems and marine life.

The organic particles formed in the atmosphere from hydrocarbons that were released as surface oil evaporated, and they got bigger as they traveled in the plume. The atmospheric plume was about 30 kilometers wide—about 18.5 miles—when it reached the coast.

Some of the hydrocarbons from the evaporating oil reacted with nitrogen oxides in the atmosphere to create ozone pollution, but this other atmospheric plume was only 3 to 4 kilometers (2 to 3 miles) wide at the coast.

“The levels of ozone were similar to what occurs in large urban areas. During the oil spill, it was like having a large city’s worth of pollution appear out in the middle of the Gulf of Mexico,” said Daniel M. Murphy, NOAA scientist at ESRL/CSD and a co-author of the study.

The relatively small amounts of nitrogen oxides in the vicinity of the oil spill (which included nitrogen oxides emitted by the spill cleanup and recovery efforts) limited the amount of polluting ozone that was formed offshore. When the excess hydrocarbons reached the coast, they could have reacted with onshore sources of nitrogen oxides, such as cars and power plants, to form additional ozone.

The researchers gathered data in June 2010 on two flights of NOAA’s WP-3D research aircraft that was outfitted to be a “flying chemical laboratory.” They also analyzed data gathered on ships in the vicinity and at two monitoring sites in Mississippi downwind of the oil spill.

They used a regional air quality model to project the path of the particle pollution, and found that time periods when the pollution plume was predicted to have reached the coast matched up well with a few short periods of high readings at the monitoring sites.

In addition to the organic particles that formed from the evaporating oil, soot particles were lofted into the atmosphere from the oil that was burned on the surface.

The authors noted that their findings could help air quality managers anticipate the effects of future oil spills. The depth of the Deepwater Horizon spill, about a mile beneath the surface, limited the effects on air quality because some hydrocarbons, such as benzene, largely dissolved in the water.

“It was fortunate that the effects on air quality of the Deepwater Horizon oil spill were limited in scope,” said Middlebrook. “Our findings show that an oil spill closer to populated areas, or in shallower waters, could have a larger effect.”

The new paper, "Air Quality Implications of the Deepwater Horizon Oil Spill," has 25 co-authors from NOAA ESRL and CIRES. For more information, visit the Proceedings of the National Academy of Sciences website.

Katy Human, CIRES,, 303-735-0196

Study shows less hail, more rain in region’s future, with possible increase in flood risk

Summertime hail could all but disappear from the eastern flank of Colorado’s Rocky Mountains by 2070, according to a new modeling study by scientists from the Cooperative Institute for Research in Environmental Sciences (CIRES), NOAA and several other institutions.

Less hail damage could be good news for gardeners and farmers, said lead author Dr. Kelly Mahoney, a research scientist at CIRES, but a shift from hail to rain can also mean more runoff, which could raise the risk of flash floods.

“In this region of elevated terrain, hail may lessen the risk of flooding because it takes awhile to melt,” Dr. Mahoney said. “Decision makers may not want to count on that in the future.”

For the new study, published this week in the journal Nature Climate Change, Dr. Mahoney and her colleagues used “downscaling” techniques to try to understand how climate change might affect hail-producing weather patterns across Colorado.

The research focused on storms involving relatively small hailstones (up to pea-sized) on Colorado’s Front Range, a region that stretches from the foothill communities of Colorado Springs, Denver and Fort Collins up to the Continental Divide. Colorado’s most damaging hailstorms tend to occur further east and involve larger hailstones not examined in this study.

In the summer in Colorado’s Front Range above about 7,500 feet, precipitation commonly falls as hail. Decision makers concerned about the safety of mountain dams and flood risk have been interested in how climate change may affect the amount and nature of precipitation in the region.

Dr. Mahoney and her colleagues began exploring that question with results from two climate models, which assumed that levels of climate-warming greenhouse gases will continue to increase in the future, from about 390 ppm today to 620 ppm in 2070.

But the weather processes that form hail – thunderstorm formation, for example – occur on much smaller scales than can be reproduced by global climate models. So the team “downscaled” the global model results twice: first to regional-scale models that can take regional topography and other details into account (this step was completed as part of the National Center for Atmospheric Research’s North American Regional Climate Change Assessment Program.) Then, the regional results were downscaled to weather-scale models that can resolve individual storms and even the in-cloud processes that create hail. 

Finally, the team compared the hailstorms of the future (2041-2070) to those of the past (1971-2000) as captured by the same sets of downscaled models. Results were similar in experiments with both climate models. 

“We found a near elimination of hail at the surface,” Mahoney said.

In the future, increasingly intense storms may actually produce more hail inside clouds, the team found. However, because those relatively small hailstones fall through a warmer atmosphere, they melt quickly, falling as rain at the surface or evaporating back into the atmosphere. In some regions, simulated hail fell through an additional 1,500 feet (~450 m) of above-freezing air in the future, compared to the past. 

The research team also found evidence that precipitation events over Colorado become more extreme in the future, while changes in hail may depend on the size of the hail stones - results that will be explored in more detail in ongoing work. 

Dr. Mahoney’s postdoctoral research was supported by the PACE program (Postdocs Applying Climate Expertise) administered by the University Corporation for Atmospheric Research and funded by CIRES Western Water Assessment, NOAA, and the U.S. Bureau of Reclamation. PACE connects young climate scientists with real-world problems such as those faced by water resource managers.

Co-authors of the new paper, “Changes in hail and flood risk in high-resolution simulations over the Colorado Mountains,” include James Scott and Joseph Barsugli (CIRES/NOAA), Michael Alexander (NOAA/Earth System Research Laboratory) and Gregory Thompson (National Center for Atmospheric Research).

Kelly Mahoney, CIRES, 
Katy Human, CIRES, 303-735-0196,

By combining detailed chemical measurements in the deep ocean, in the oil slick, and in the air, scientists from the Cooperative Institute for Research in Environmental Sciences (CIRES), NOAA and other academic institutes have independently estimated how fast gases and oil were leaking during the 2010 Deepwater Horizon oil spill in the Gulf of Mexico.

The new chemistry-based spill rate estimate, an average of 11,130 tons of gas and oil compounds per day, is close to the official average leak rate estimate of about 11,350 tons of gas and oil per day (equal to about 59,200 barrels of liquid oil per day).

“This study uses the available chemical data to give a better understanding of what went where, and why,” said Thomas Ryerson, a NOAA research chemist and lead author of the study. “The surface and subsurface measurements and analysis provided by our university colleagues were key to this unprecedented approach to understanding an oil spill.”

The NOAA-led team did not rely on any of the data used in the original estimates, such as video flow analysis, pipe diameter and fluid flow calculations. “We analyzed a completely separate set of chemical measurements, which independently led us to a very similar leak estimate,” Ryerson said.

The new study, Chemical data quantify Deepwater Horizon hydrocarbon flow rate and environmental distribution, was published online today in the journal Proceedings of the National Academy of Sciences USA.

The new analysis follows on another NOAA-led study published earlier this year, in which Ryerson and colleagues estimated a lower limit to the Deepwater Horizon leak rate based on two days of airborne data collected during the spill and the chemical makeup of the reservoir gas and oil determined before the spill. The new analysis adds in many other sources of data, including subsurface and surface samples taken during six weeks of the spill and including a direct measure of the makeup of the gas and oil actually leaking into the Gulf.

Ryerson and his colleagues found that the leaking gas and oil quickly separated into three major pools: the underwater plume about 3,300-4,300 feet below the surface, visible surface slick, and an airborne plume of evaporating chemicals. Each pool had a very different chemical composition.

The underwater plume was enhanced by gases known to dissolve readily in water, the team found. This includes essentially all of the lightweight methane (natural gas) and benzene (a known carcinogen) present in the spilling reservoir fluid. The surface oil slick was dominated by the heaviest and stickiest components, which neither dissolved in seawater nor evaporated into the air. And the airborne plume of chemicals contained a wide mixture of intermediate-weight components of the spilled gas and oil.  

The visible surface slick represented about 15 percent of the total leaked gas and oil; the airborne plume accounted for about another 7 percent. About 36 percent remained in a deep underwater plume, and 17 percent was recovered directly to the surface through the marine riser. The balance, about 25 percent of the total, is not directly accounted for by the chemical data.

This information about the transport and fate of different components of the spilled gas and oil mixture could help resource managers and others trying to understand environmental exposure levels.

The chemical measurements made from mid-May through June showed that the composition of the atmospheric plume changed very little, suggesting little change in the makeup of the leaking gas and oil.

The team of researchers also used the detailed chemical measurements to calculate how much gas and oil, in total, was spilling from the breached reservoir deep underwater.
The new chemistry-based estimate of 11.130 tons per day has an estimated range of 8,900 to 13,300 tons per day. By comparison, the official estimated range was 10,000 to 12,700 tons per ay.

CIRES Co-authors of the new paper, “Chemical data quantify Deepwater Horizon hydrocarbon flow rate and environmental distribution,” are J.A. de Gouw, J. Peischl and C. Warneke. 

Joost de Gouw, CIRES, 303-497-3878,
Jane Palmer, CIRES science writer, 303-492-6289,

The Rio Grande Rift—the north-trending continental rift zone that extends from Colorado’s central Rocky Mountains to Mexico—is not dead but geologically alive and active, according to a new study by scientists at the Cooperative Institute for Research in the Environmental Sciences (CIRES) in collaboration with the University of New Mexico, New Mexico Tech, Utah State University, and UNAVCO. 

“We don’t expect to see a lot of earthquakes, or big ones, but we will have some earthquakes,” said author Anne Sheehan, CIRES Fellow and Associate Director of CIRES Solid Earth Sciences Division.

Along the rift, spreading motion in the crust has led to the rise of magma—the molten rock material under Earth’s crust—to the surface, and to the creation of long, fault-bounded basins that are susceptible to earthquakes. Sheehan and her team, along with colleagues at the University of New Mexico, studied the region to assess the potential earthquake hazards.

Using semi-permanent Global Positioning System instruments at 25 sites in Colorado and New Mexico, the team tracked the rift's miniscule movements from 2006 to 2011. “Questions we wanted to answer are: how is the Rio Grande Rift deforming? Is it alive or dead? Is it opening or not?” Sheehan said.

The high-precision instrumentation has provided unprecedented data about the volcanic activity in the region as the slow rates of motion had made previous attempts to determine tectonic activity particularly challenging, she said.  Previously, geologists had estimated the rift had spread apart by up to 5 millimeters each year but the errors introduced by the measuring instrumentations were significant. “The GPS has reduced the uncertainty dramatically,” she said. “This is the first real set of real space geodetic measurements in this area.”

Using the high-precision instrumentation, the scientists found an average strain rate of 1.2 nanostrain each year across the experimental area. A nanostrain is a change in length of one part per billion, thus 1.2 nanostrain per year is equivalent to 1.2 mm/yr extension over a 1000 km length.  “It is lower than we thought but it does exist,” Sheehan said. “Some people thought it was zero but we are seeing things are extending slowly.”

The researchers also found the extensional deformation—stretching— is not concentrated in a narrow zone centered on the Rio Grande Rift but is distributed broadly from the western edge of the Colorado Plateau well into the western Great Plains. “The surprising thing to come out of the study was that the strain was spread out,” Sheehan said. The results of the study are published in the January edition of Geology

This finding sheds some light on the mystery of how continents deform away from plate boundaries, Sheehan said. At plate boundaries scientists can observe what is going on pretty clearly, she said. “Things move past each other and crash into each other—at active plate boundaries the rates of motion detected by GPS can be centimeters per year—compare that with the fraction of a millimeter per year that we have measured for the Rio Grande Rift.”

The team plans to continue monitoring the Rio Grande Rift, probing whether the activity remains constant over time, said lead author Henry Berglund of UNAVCO, who was a graduate student at CIRES when he completed this stage of the research. Also, the scientists may attempt to determine vertical as well as horizontal activity, to determine whether the Rocky Mountains are still uplifting or not, he said.  

“Present day measurements of deformation within continental interiors have been difficult to capture due to the typically slow rates of deformation within them,” Berglund said. “Now, with the recent advances in space geodesy, we are finding some very surprising results in these previously unresolved areas.”

As far as the potential for future earthquakes in the region, the study’s results are unequivocal, however. “The rift is still active,” Sheehan said.

The new paper, " Distributed deformation across the Rio Grande Rift, Great Plains, and Colorado Plateau,” is also authored by CIRES Fellow Steven Nerem, UNAVCO’s Frederick Blume, Anthony Lowry of the Department of Geology at Utah State University, Mousumi Roy of the Department of Earth and Planetary Sciences at the University of New Mexico, and Mark Murray of the Department of Earth and Environmental Science at New Mexico Tech.

The National Science Foundation provided the funding for this study and EarthScope and UNAVCO provided instruments, equipment and engineering services.