Dust Deposition on Snow

Courtesy of whiteriverwild.org

photo courtesy of whiteriverwild.org

Welcome to the Dust Deposition on Snow section of SDSG. Here you will find an assortment of information pertaining to the occurrences of dust-on-snow. This is not a source of original material but rather a combination of excerpts from scientific and popular press articles as well as a portal to a plethora of valuable information.  None of the scientists mentioned are affiliated in any manner with SDSG.  Their work is merely being referenced.  Our goal is to provide a “one-stop-shop” for all relevant material dealing with dust and snow.  We emphasize information related to the area in which we are located, the state of Colorado.

DUST DEPOSITION ON SNOW MENU: IntroductionPoints of Impact | Points of Origin | Current Situation | Historical Information | Implications for Sustainability | Future Outlook | Useful Links | Mass Media | Recommended Scientific Articles | References Cited

Introduction:

What are the dust events?

Dust deposition on the mountains of Colorado has received growing attention over the past several years. While these events are not new occurrences, they have only been extensively studied for the past 20+ years. The issue is large plumes of dust that are carried predominantly from the Colorado Plateau region, an area spanning the Four Corners region of the western United States, and deposited onto the mountain ranges throughout the state.

Colorado Plateau Region

The Colorado Plateau Region–Credit to NPS.gov

While the origins of the dust storms have been determined, the exact cause or causes have not been scientifically identified. These dust events not only cause a decrease in the aesthetically pleasing views of the Colorado landscape, but they have distressing implications to the ecosystems, economies, and social aspects of the affected areas.

Why is the dust an issue?

 

The deposited dust drastically reduces the albedo, or reflectivity, of the snow. As a result, the snow absorbs more of the incoming solar radiation from the sun and thus melts quicker and sooner than a clean snowpack. This creates problems for the cities, industries, individuals, plants, and animals that rely on a slow-melting snowpack to provide them with water throughout the dry summer months. Instead, water is coming much sooner and more abundant than water managers are accustomed to. Although the dust storms are not the only contributing factor to earlier snowmelt, they are certainly a major catalyst for the snow to melt sooner.

The dust events exacerbate a growing problem in the western United States, earlier and more rapid snowmelt. This has implications for the concept of sustainability because it puts growing stress on the environment and people that rely on the water for a plethora of reasons.

The issue of dust deposition is not only an ecological issue but it also has implications to the strength and productivity of the livelihoods of people living in the Colorado River Basin. The Colorado River provides water to 40 million people in seven western states and two countries and irrigates 5.5 million acres of land (Deems et. al, 2013). The main water source of the Colorado River comes from alpine mountain areas (Deems et. al, 2013). The river has long been over-allocated and the occurrence of increased dust deposition is heightening the issues of water scarcity (Deems et. al, 2013). Decreased snow albedo from anthropogenic dust loading to the Colorado Mountains has shortened the duration of snowpack by several weeks relative to conditions prior to western expansion (Deems et. al, 2013). Dust from the Colorado Plateau has shortened the snow cover durations at high alpine sites by 25-50 days (Painter et. al, 2007). The most extreme projections of dust loading predict the reduction of 1% of the Colorado River’s annual flow volume (Deems et. al, 2013).

For example, farmers rely on continuous water flows throughout the summer to irrigate their crops. Ranchers depend on the availability of water to keep their animals healthy and hydrated.  Ski areas need a clean, aesthetically pleasing spring snowpack on which people can ski.  With the severity and frequency of dust events increasing during the past several years, the ability for future water users to meet their needs during the arid summer months may be more of an issue than once expected. In fact, the number of dust storms has varied with an overall increase since they have been monitored.

Total Dust on Snow events 2004-2017

Total Dust on Snow events 2004-2017

Above is a graph displaying the number of dust events since Total Dust-on-Snow Events (wet and dry dust events) in the Senator Beck Basin Study Area, San Juan Mountains, CO.

 

What Are Differences Between Wet And Dry Dust Events?

There are two types of dust deposition that affect the snowpack in Colorado. Wet deposition which is the input of nutrient in an ecosystem in a dissolved state. Wet deposition usually occurs through rainfall in most systems but in the case of dust deposition transportation in the mountains of Colorado, snow is the leading source of wet deposition.

 

Dry deposition is the variable form of dust deposition to occurring the mountains of Colorado  from year to year as seen on the graph display above, Total Dust-on-Snow Events (wet and dry dust events) in the Senator Beck Basin Study Area, San Juan Mountains, CO. Dry deposition is an input of nutrients in an ecosystem in the particulate state. It usually occurs through dust foil and in the case of the mountains of Colorado is the typical form on deposition.

What Is Exactly Dust Deposition?

Dust is small, dry, solid particles projected into the air by natural forces such as volcanic eruption and wind. Dust can also be projected into the air through mechanical or man-made processes such as milling, drilling, conveying, bagging, sweeping, and demolition (IUPC, 1990). Dust particles vary in size but are usually between 1 to 100 micrometers in diameter (IUPC, 1990). Particles larger than PM10 dominate total atmosphere particle loads are not measured and this size particle would include the fine particulate matter of dust deposition (Brahney et. al, 2013). Presently, desert dust particles or dust deposition are not measured by the National Atmospheric Deposition Program on a regular basis. Also, measurements of total particle concentrations in southeastern Utah and western Colorado are not regularly measured (Brahney et. al, 2013).

Who are some of the leading scientists and institutions conducting research?

Dr. Thomas PainterJet Propulsion Laboratory, California Institute of Technology/ California Institute of Technology

  • Email Dr. Painter at: Thomas.Painter at jpl.nasa.gov

 

Dr. Jeffrey DeemsExecutive Director, Center for Snow and Avalanche Studies (CSAS)

  • Email Dr. Deems at: jdeems at snowstudies.org

 

Chris LandryFormer Director, Center for Snow and Avalanche Studies (CSAS)

  • Email Landry at: clandry at snowstudies.org

 

Dr. Richard Reynolds–U.S. Geological Survey

  • Email Dr. Reynolds at: rreynolds at usgs.gov

 

Dr. Jason NeffUniversity of Colorado at Boulder

  • Email Dr. Neff at: neffjc at colorado.edu

 

Dr. Heidi SteltzerFort Lewis College

  • Email Dr. Steltzer at: steltzer_h at fortlewis.edu

 

Dr. Jayne BelnapWatershed Sciences Assistant Profesor, Utah State University

  • Email Dr. Belnap at: janice.brahney at usu.edu

 

Dr. Corey LawrenceU.S. Geological Survey

  • Email Dr. Lawrence at: clawrence at usgs.gov

DUST DEPOSITION ON SNOW MENU: IntroductionPoints of Impact | Points of Origin | Current Situation | Historical Information | Implications for Sustainability | Future Outlook | Useful Links | Mass Media | Recommended Scientific Articles | References Cited

Text Box: Figure 1 displays the reflective difference between clean and dirty (dust-laden) snow in the San Juan Mountains of Colorado [courtesy of Painter et al., 2007]

The dust emanating from the Colorado Plateau region is deposited across the state of Colorado. While the dust events are heavily studied in the San Juan Mountains, they have been shown to deposit dust near Denver mountain ranges. Although significantly farther from the Colorado Plateau region than the San Juans, the dust events occurring nearer to Denver are just as severe as those which occur nearer the source area (Best, 2008). In 2009, which received a record total of 12 significant dust events since records began being kept in 2003, dust was found across the state following each event (Colorado Daily Staff, 2009).

Effects on Snow

Dust deposited on snow greatly reduces the snow’s ability to reflect the sun’s incoming solar radiation. Normally snow has the highest reflective properties of any natural substance on Earth (Painter et al., 2007). As shown in Figure 1 below, clean snow reflects 80-100% of incoming visible light. However, once dust has been deposited on the snow surface, the snow only reflects 50-60% of incoming visible light.

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Figure 1 displays the reflective difference between clean and dirty (dust-laden) snow in the San Juan Mountains of Colorado–Taken from the presentation “How desert dust is influencing Colorado snowmelt” by Landry, Painter, and Barrett

Decreasing the albedo of the snow, thus increasing the absorption of solar radiation, causes the snow to melt at an unnaturally high rate. In 2006, dust-laden alpine snowpack melted up to 35 days sooner than a clean snowpack (Painter et al., 2007). In 2009, dust events led to the snowpack melting nearly 50 days sooner than a clean snowpack (Berwyn, 2009).

Below are two images (Figure 2) displaying the San Juan Mountains. The first image was taken on April 12, 2005, after four dust events, via the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite. The second image was taken on April 12, 2006, after eight dust events, via MODIS on NASA’s Terra satellite. Comparing the two images, one can see evidence the snowpack in 2006, which had double the amount of dust events, had a much smaller spatial extent than at the same time in 2005. The abundance of dust as well as weather conditions (e.g. minimal cloud cover) allowed the snowpack to receive ample sunlight and melt at a quicker pace (Dust Reduces Snow Cover in the San Juans, 2007).

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Figure 2 displays the San Juan Mountains on April 12, 2005 and April 12, 2006 respectively. The 2006 image shows a reduction in the snowpack’s spatial extent compared to the 2005 image–Credit to NASA (http://earthobservatory.nasa.gov/IOTD/view.php?id=7842)

“Frequency of dust deposition and radiative forcing doubled when the Colorado Plateau, the dust source region, experienced intense drought (8 events and 39-59 Watts per square meter in 2006) versus a year with near normal precipitation (4 events and 17-34 Watts per square meter in 2005)” (Painter et al., 2007).

Impacts for Skiers

The dust not only causes the snow to melt quicker, but it creates unfavorable conditions for recreational use. The owner of Pine Needle Mountaineering in Durango, CO, Keith Roush, is quoted saying, “we haven’t skied as much this spring [2009], because the dust stops you dead in your tracks. It slows you down and throws you off balance. It’s like hitting sand” (Colorado Daily Staff, 2009). Lisa Branner of Venture Snowboards in Silverton, CO has said “the dust is definitely trashing the snowpack causing it to heat up, rot out and melt faster — shortening what could have been a great spring touring season” (Huffman, 2010). Chris Landry, one of the leading scientists studying the effects of dust deposition on snow, has said, “the last several years have been very disappointing as a skier, especially last year [2009] when you were, in effect, trying to ski on mud. It’s no fun” (Huffman, 2010).

Biological Impacts

“Seasonal snow cover has a substantial effect on ecosystem function where freezing temperatures over winter facilitate the formation and retention of a snow pack. It protects and sustains plant and soil communities by moderating temperatures during winter and later by supplying a source of water to fuel plant growth at the start of the growing season. The timing of snowmelt also regulates the timing of early season phenological events [flowering and growing] and can affect reproductive output” (Steltzer et al., 2009).

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Dust storms leading to earlier snowmelt may affect the timing of flowering

“In an alpine basin in the San Juan Mountains, the researchers [Steltzer et al.] simulated dust effects on snowmelt in experimental plots. They measured dust’s acceleration of snowmelt on the life cycles of alpine plants. The timing of snowmelt signals to mountain plants that it’s time to start growing and flowering. When dust causes early snowmelt, plant growth does not necessarily begin soon after the snow is gone” (NSF, 2009).

When dust deposition causes snowpack to melt sooner, plant activity is postponed until ambient air temperatures have warmed to above freezing temperatures. Dr. Heidi Steltzer, a biology professor at Fort Lewis College has said, “Climate warming could therefore have a greater effect on the timing of growth and flowering” (O’Donoghue, 2009). Futhermore, Dr. Steltzer stated, “Desert dust alters the ecology of alpine landscapes from staggered to more synchronized plant growth. With increasing dust deposition from drying and warming in the deserts under global warming, the composition of alpine meadows could change as some species increase in abundance, while others are lost, possibly forever”(NSF, 2009). The synchronization of plants also “…could increase nutrient losses to aquatic ecosystems before greening and alter species interactions” (Steltzer et al., 2009).

Lastly, Steltzer et al. (2009) concluded:

“Synchronized life histories across a landscape could decrease nutrient retention by reducing temporal variation in nutrient demand among topographic positions. In particular, delayed phenology after snowmelt would postpone plant demand for resources, leading to decreased nutrient retention when nutrient availability is high. During the growing season, concurrent growth and flowering across the landscape could alter species interactions, increasing competition for limiting resources and pollinators and changing landscape-scale gene flow via pollination. Decreased spatial variation in plant phenology can also reduce foraging success by large herbivores with consequences for offspring production. Thus, the atmospheric transport of desert dust is a process that links human activities in desert ecosystems to changes in phenology in alpine landscapes, which could affect biotic interactions and nutrient cycling by synchronizing phenology across the tundra.”

Implications of Earlier Snowmelt

“If the shifts in snowmelt timing…continue, they have important implications for reservoir operation and flood risk, water rights, wildfire severity, and forest ecology in Colorado. Snowmelt will occur earlier, but the runoff season may increase in length, which could reduce the risk of flooding during snowmelt. On the other hand, flood risk might increase if warming temperatures cause Colorado to experience more rain-on-snow events, which have been relatively uncommon in the state compared to the Pacific Northwest. Changes in snowmelt timing may affect water rights whose seniority varies with time of year. Stakeholders whose water rights are senior late in the year, but are more junior early in the year, may be losers under scenarios of increased springtime warming. Earlier snowmelt may cause soil moisture to decline during summer, increasing drought stress in trees, making them more susceptible to wildfires and insect infestation” (Clow, 2009).

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Dust deposited on snow–Credit to the Center for Snow & Avalanche Studies

In a study conducted by Tim Barnett of the Scripps Institution of Oceanography to research the effect climate change could potentially have on water resources in the western U.S., they found:

“Even by mid-century we see that the Colorado River Reservoir System will not be able to meet all of the demands placed on it, including water supply for Southern California and the inland Southwest, since reservoirs levels will be reduced by over one-third and releases reduced by as much as 17%. The greatest effects will be on lower Colorado River Basin states. All users of Colorado River hydroelectric power will be affected by lower reservoir levels and flows, which will result in reductions in hydropower generation by as much as 40%. Basically, we found the fully allocated Colorado system to be at the brink of failure, wherein virtually any reduction in precipitation over the Basin, either natural or anthropogenic, will lead to the failure to meet mandated allocations” (Barnett et al., 2004).

Earlier snowmelt affects ranchers and farmers who depend on a slow-melting snowpack to provide them with water throughout the summer (Streater, 2009).

“Colorado — which is under an agreement with the Bureau of Reclamation to divert roughly 38 million gallons a year from the San Juan River Basin to thirsty cities in New Mexico, including Albuquerque and Santa Fe — now fears it may not be able to meet the terms of the water transfer agreement as the snow melt arrives early and flows downstream” (O’Donoghue, 2009).

Effects on Ecosystems

“Eolian dust mobilized from arid-land soils generally contains high concentrations of base cations, and dust typically has high concentrations of N [nitrogen] and P [phosphorus], as well as elevated concentrations of a range of atmospheric pollutants. High-elevation lakes and tundra ecosystems are generally low in nutrient content and vulnerable to increases in atmospheric deposition. There is strong evidence for the impacts of changing N deposition in high-elevation settings, as well as suggestions of increasing P and base-cation deposition into high-elevation settings” (Neff et al., 2008).

“There is evidence from a range of other settings that base-cation loading via dust deposition can change precipitation and surface-water alkalinity. The relatively large perturbation to base-cation loading to these lakes suggests that dust inputs could be one factor mitigating the lake impacts of generalized regional increases in acid deposition” (Neff et al., 2008).

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A dust storm engulfs Phoenix–Credit to Clayton Esterson

“Dust inputs can alter soil fertility significantly and thus affect many ecosystem properties, including plant-community composition and productivity. As soils age, the supply of soil nutrients from minerals declines unless replaced by other inputs, such as dust. Dust may contain not only many plant-essential nutrients (e.g., Na, P, K, and Mg), but also substances that affect the availability of these nutrients (e.g., carbonates). P, which is commonly a limiting nutrient in desert soils, can govern plant productivity as well as affect carbon and nitrogen mineralization rates in deserts. K and Mg may strongly influence plant-community composition in semiarid areas. Even small increases in the proportion of fine particles, or in some nutrients, may increase invasibility by exotic annual plants” (Reynolds et al., 2001).

“The future nutrient load in the soils of the central Colorado Plateau thus depends on the balance of nutrients lost and regained, as well as composition of future dust inputs, all of which will be influenced by climatic variability and human activity as they modify southwestern landscapes” (Reynolds et al., 2001).

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Dust loading can lead to eutrophication of streams and lakes

“Dust inputs can alter soil fertility significantly and thus affect many ecosystem properties, including plant-community composition and productivity. As soils age, the supply of soil nutrients from minerals declines unless replaced by other inputs, such as dust” (Reynolds et al., 2001).

“…CU-Boulder researchers have observed increased algal growth in streams and lakes as a result of rising nitrogen deposition, as well as changes in the composition and diversity of wildflowers on the tundra. “Because these types of inputs have the potential to increase plant growth, the ultimate outcome of such depositions could change the fabric of our ecosystems,” said Neff” (EurekAlert, 2008).

“Because soil nutrients (eg nitrogen, phosphorus) and organic matter are often associated with smaller soil particles, soil fertility in dust source areas becomes depleted while sink areas are concomitantly enriched” (Field et al., 2009).

Below are two images (Figure 2) displaying the San Juan Mountains.The first image was taken on April 12, 2005, after four dust events, via the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite.The second image was taken on April 12, 2006, after eight dust events, via MODIS on NASA’s Terra satellite.Comparing the two images, one can see evidence the snowpack in 2006, which had double the amount of dust events, had a much smaller spatial extent than at the same time in 2005.The abundance of dust as well as weather conditions (e.g. minimal cloud cover) allowed the snowpack to receive ample sunlight and melt at a quicker pace[1].

3 Responses to “Dust Deposition on Snow”

  1. Luke says:

    this is really great work, Dominic.

    You should be very proud of it.

    Luke

  2. Kelli says:

    Fantastic work.

  3. Dust Guy says:

    Very informative and well executed website on the dusty snow issue. The scenario is laid out in a logical manner and is easy to follow and comprehend. Well done!