The oldest ice core

<IMG SRC="/Images/571096301.jpg" WIDTH="350" HEIGHT="278" BORDER="0" ALT="This shows Antarctic locations (in bright blue) where 1.5 million years old ice could exist. The figure is modified from Van Liefferinge and Pattyn (Climate of the Past, 2013). – Van Liefferinge and Pattyn”>
This shows Antarctic locations (in bright blue) where 1.5 million years old ice could exist. The figure is modified from Van Liefferinge and Pattyn (Climate of the Past, 2013). – Van Liefferinge and Pattyn

How far into the past can ice-core records go? Scientists have now identified regions in Antarctica they say could store information about Earth’s climate and greenhouse gases extending as far back as 1.5 million years, almost twice as old as the oldest ice core drilled to date. The results are published today in Climate of the Past, an open access journal of the European Geosciences Union (EGU).

By studying the past climate, scientists can understand better how temperature responds to changes in greenhouse-gas concentrations in the atmosphere. This, in turn, allows them to make better predictions about how climate will change in the future.

“Ice cores contain little air bubbles and, thus, represent the only direct archive of the composition of the past atmosphere,” says Hubertus Fischer, an experimental climate physics professor at the University of Bern in Switzerland and lead author of the study. A 3.2-km-long ice core drilled almost a decade ago at Dome Concordia (Dome C) in Antarctica revealed 800,000 years of climate history, showing that greenhouse gases and temperature have mostly moved in lockstep. Now, an international team of scientists wants to know what happened before that.

At the root of their quest is a climate transition that marine-sediment studies reveal happened some 1.2 million years to 900,000 years ago. “The Mid Pleistocene Transition is a most important and enigmatic time interval in the more recent climate history of our planet,” says Fischer. The Earth’s climate naturally varies between times of warming and periods of extreme cooling (ice ages) over thousands of years. Before the transition, the period of variation was about 41 thousand years while afterwards it became 100 thousand years. “The reason for this change is not known.”

Climate scientists suspect greenhouse gases played a role in forcing this transition, but they need to drill into the ice to confirm their suspicions. “The information on greenhouse-gas concentrations at that time can only be gained from an Antarctic ice core covering the last 1.5 million years. Such an ice core does not exist yet, but ice of that age should be in principle hidden in the Antarctic ice sheet.”

As snow falls and settles on the surface of an ice sheet, it is compacted by the weight of new snow falling on top of it and is transformed into solid glacier ice over thousands of years. The weight of the upper layers of the ice sheet causes the deep ice to spread, causing the annual ice layers to become thinner and thinner with depth. This produces very old ice at depths close to the bedrock.

However, drilling deeper to collect a longer ice core does not necessarily mean finding a core that extends further into the past. “If the ice thickness is too high the old ice at the bottom is getting so warm by geothermal heating that it is melted away,” Fischer explains. “This is what happens at Dome C and limits its age to 800,000 years.”

To complicate matters further, horizontal movements of the ice above the bedrock can disturb the bottommost ice, causing its annual layers to mix up.

“To constrain the possible locations where such 1.5 million-year old – and in terms of its layering undisturbed – ice could be found in Antarctica, we compiled the available data on climate and ice conditions in the Antarctic and used a simple ice and heat flow model to locate larger areas where such old ice may exist,” explains co-author Eric Wolff of the British Antarctic Survey, now at the University of Cambridge.

The team concluded that 1.5 million-year old ice should still exist at the bottom of East Antarctica in regions close to the major Domes, the highest points on the ice sheet, and near the South Pole, as described in the new Climate of the Past study. These results confirm those of another study, also recently published in Climate of the Past.

Crucially, they also found that an ice core extending that far into the past should be between 2.4 and 3-km long, shorter than the 800,000-year-old core drilled in the previous expedition.

The next step is to survey the identified drill sites to measure the ice thickness and temperature at the bottom of the ice sheet before selecting a final drill location.

“A deep drilling project in Antarctica could commence within the next 3-5 years,” Fischer states. “This time would also be needed to plan the drilling logistically and create the funding for such an exciting large-scale international research project, which would cost around 50 million Euros.”

Antarctic ice core sheds new light on how the last ice age ended

Brian Bencivengo, assistant curator of the National Ice Core Laboratory, in Lakewood, Colo., holds a one-meter-long section of the West Antarctic Ice Sheet (WAIS) Divide Ice Core. -  Geoffrey Hargreaves, National Science Foundation
Brian Bencivengo, assistant curator of the National Ice Core Laboratory, in Lakewood, Colo., holds a one-meter-long section of the West Antarctic Ice Sheet (WAIS) Divide Ice Core. – Geoffrey Hargreaves, National Science Foundation

Analysis of an ice core taken by the National Science Foundation- (NSF) funded West Antarctic Ice Sheet (WAIS) Divide drilling project reveals that warming in Antarctica began about 22,000 years ago, a few thousand years earlier than suggested by previous records.

This timing shows that West Antarctica did not “wait for a cue” from the Northern Hemisphere to start warming, as scientists had previously supposed.

For more than a century scientists have known that Earth’s ice ages are caused by the wobbling of the planet’s orbit, which changes its orientation to the sun and affects the amount of sunlight reaching higher latitudes.

The Northern Hemisphere’s last ice age ended about 20,000 years ago, and most evidence had indicated that the ice age in the Southern Hemisphere ended about 2,000 years later, suggesting that the South was responding to warming in the North.

But research published online Aug. 14 in the journal Nature shows that Antarctic warming began at least two, and perhaps four, millennia earlier than previously thought.

Most previous evidence for Antarctic climate change had come from ice cores drilled in East Antarctica, the highest and coldest part of the continent. However, a U.S.-led research team studying the West Antarctic core found that warming there was well underway 20,000 years ago.

WAIS Divide is a large-scale and multi-year glaciology project supported by the U.S. Antarctic Program (USAP), which NSF manages. Through USAP, NSF coordinates all U.S. science on the southernmost continent and aboard vessels in the Southern Ocean and provides the necessary logistics to make the science possible.

The WAIS Divide site is in an area where there is little horizontal flow of the ice, so the data are known to be from a location that remained consistent over long periods.

The WAIS Divide ice core is more than two miles deep and covers a period stretching back 68,000 years, though so far data have been analyzed only from layers going back 30,000 years. Near the surface, one meter of snow is equal to a year of accumulation, but at greater depths the annual layers are compressed to centimeters of ice.

“Sometimes we think of Antarctica as this passive continent waiting for other things to act on it. But here it is showing changes before it ‘knows’ what the North is doing,” said T.J. Fudge, a University of Washington doctoral student in Earth and Space Sciences and lead corresponding author of the Nature paper. Fudge’s 41 co-authors are other members of the WAIS project.

Fudge identified the annual layers by running two electrodes along the ice core to measure higher electrical conductivity associated with each summer season. Evidence of greater warming turned up in layers associated with 18,000 to 22,000 years ago, the beginning of the last deglaciation.

“This deglaciation is the last big climate change that we’re able to go back and investigate,” he said. “It teaches us about how our climate system works.”

West Antarctica is separated from East Antarctica by a major mountain range. East Antarctica has a substantially higher elevation and tends to be much colder, though there is recent evidence that it too is warming.

Rapid warming in West Antarctica in recent decades has been documented in previous research by Eric Steig, a professor of Earth and Space Sciences at the University of Washington who serves on Fudge’s doctoral committee and whose laboratory produced the oxygen isotope data used in the Nature paper. The new data confirm that West Antarctica’s climate is more strongly influenced by regional conditions in the Southern Ocean than East Antarctica is.

“It’s not surprising that West Antarctica is showing something different from East Antarctica on long time scales, but we didn’t have direct evidence for that before,” Fudge said.

He noted that the warming in West Antarctica 20,000 years ago is not explained by a change in the sun’s intensity. Instead, how the sun’s energy was distributed over the region was a much bigger factor. It not only warmed the ice sheet but also warmed the Southern Ocean that surrounds Antarctica, particularly during summer months when more sea ice melting could take place.

Changes in Earth’s orbit today are not an important factor in the rapid warming that has been observed recently, he added. “Earth’s orbit changes on the scale of thousands of years, but carbon dioxide today is changing on the scale of decades so climate change is happening much faster today,” Fudge said.

Julie Palais, the Antarctic Glaciology Program director in NSF’s Division of Polar Programs, said new findings will help scientists to “better understand not only what happened at the end of the last ice age but it should also help inform our understanding of what might be happening as the climate warms and conditions begin to change in and around the Antarctic continent.”

She added, “West Antarctica is currently experiencing some of the largest changes on the continent, such as the large calving events in the Amundsen Sea Embayment linked to warm ocean currents undercutting the outlet glaciers. The recent changes are consistent with the WAIS Divide results that show West Antarctica is sensitive to changes in ocean conditions in the past.”

The depths of winter: How much snow is in fact on the ground?

Stellar dendrites are tree-like snow crystals that have branches upon branches. -  Kenneth Libbrecht, Caltech
Stellar dendrites are tree-like snow crystals that have branches upon branches. – Kenneth Libbrecht, Caltech

Equipped with specialized lasers and GPS technology, scientists are working to address a critical wintertime weather challenge: how to accurately measure the amount of snow on the ground.

Transportation crews, water managers and others who make vital safety decisions need precise measurements of how snow depth varies across wide areas.

But traditional measuring devices such as snow gauges and yardsticks are often inadequate for capturing snow totals that may vary even within a single field or neighborhood.

Now scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., and at other institutions are finding that prototype devices that use light pulses, satellite signals and other technologies offer the potential to almost instantly measure large areas of snow.

In time, such devices might provide a global picture of snow depth.

“We’ve been measuring rain accurately for centuries, but snow is much harder because of the way it’s affected by wind and sun and other factors,” says NCAR researcher Ethan Gutmann.

“It looks like new technology, however, will finally give us the ability to say exactly how much snow is on the ground.”

NCAR is conducting the effort with several collaborating organizations, including the National Oceanic and Atmospheric Administration (NOAA) and the University of Colorado Boulder.

The work is supported by NCAR’s sponsor, the National Science Foundation (NSF).

“Snow represents both a hazard and a water resource in the western states,” says Thomas Torgersen, NSF program director for hydrologic sciences. “Both require detailed assessments of snow amounts and depth. This technology will provide new and important guidance.”

Emergency managers rely on snowfall measurements when mobilizing snow plows or deciding whether to shut down highways and airports during major storms.

They also use snow totals when determining whether a region qualifies for disaster assistance.

In mountainous areas, officials need accurate reports of snowpack depth to assess the threat of avalanches or floods, and to anticipate the amount of water available from spring and summer runoff.

But traditional approaches to measuring snow can greatly underreport or overreport snow totals, especially in severe conditions.

Snow gauges may miss almost a third of the snow in a windy storm, even when they are protected by specialized fencing designed to cut down on the wind’s effects.

Snow probes or yardsticks can reveal snow depth within limited areas. But such tools require numerous in-person measurements at different locations, a method that may not keep up with totals during heavy snowfalls.

Weather experts also sometimes monitor the amount of snow that collects on flat, white pieces of wood known as snow boards, but this is a time-intensive approach that requires people to check the boards and clear them off every few hours.

The nation’s two largest volunteer efforts–the National Weather Service’s Cooperative Observer Program, and the Community Collaborative Rain, Hail, and Snow Network (CoCoRaHS)–each involve thousands of participants nationwide using snow boards, but their reports are usually filed just once a day.

More recently, ultrasonic devices have been deployed in some of the world’s most wintry regions.

Much like radar, these devices measure the length of time needed for a pulse of ultrasonic energy to bounce off the surface of the snow and return to the transmitter.

However, the signal may be affected by shifting atmospheric conditions, including temperature, humidity and winds.

The specialized laser instruments under development at NCAR can correct for such problems.

Once set up at a location, they can automatically measure snow depth across large areas. Unlike ultrasonic instruments, lasers rely on light pulses that are not affected by atmospheric conditions.

New tests by Gutmann indicate that a laser instrument installed high above treeline in the Rocky Mountains west of Boulder can measure 10 feet or more of snow with an accuracy as fine as half an inch or better.

In a little more than an hour, the instrument measures snow at more than 1,000 points across an area almost the size of a football field to produce a three-dimensional image of the snowpack and its variations in depth.

Gutmann’s next step will be to build and test a laser instrument that can measure snow over several square miles. Tracking such a large area would require a new instrument capable of taking more than 12,000 measurements per second.

“If we’re successful, these types of instruments will reveal a continually-updated picture of snow across an entire basin,” he says.

One limitation for the lasers, however, is that light pulses cannot penetrate through objects such as trees and buildings.

This could require development of networks of low-cost laser installations that would each record snow depths within a confined area.

Alternatively, future satellites equipped with such lasers might be capable of mapping the entire world from above.

Gutmann and Kristine Larson, a scientist at the University of Colorado, are also exploring how to use GPS sensors for snowfall measurements.

GPS sensors record satellite signals that reach them directly and signals that bounce off the ground.

When there is snow on the ground, the GPS signal bounces off the snow with a different frequency than when it bounces off bare soil, enabling scientists to determine how high the surface of the snow is above the ground.

Such units could be a cost-effective way of measuring snow totals; meteorologists could tap into the existing global network of ground-based GPS receivers.

However, researchers are seeking to fully understand how the density of the snow and the roughness of its surface alter GPS signals.

“Our hope is to develop a set of high-tech tools that will enable officials to continually monitor snow depth, even during an intense storm,” Larson says.

“While we still have our work cut out for us, the technology is very promising.”

Soot packs a punch on Tibetan Plateau’s climate

In some cases, soot – the fine, black carbon silt that is released from stoves, cars and manufacturing plants – can pack more of a climatic punch than greenhouse gases, according to a paper published in the journal Atmospheric Chemistry and Physics.

Researchers at the Department of Energy’s Pacific Northwest National Laboratory, the University of Michigan and NOAA found that soot landing on snow on the massive Tibetan Plateau can do more to alter snowmelt and monsoon weather patterns in Asia than carbon dioxide and soot in the air. Soot on snow causes the plateau’s annual glacial melt to happen sooner each year, causing farmers below it to have less water for their crops in the summer. In a domino effect, the melting then prods two of the region’s monsoon systems to become stronger over India and China.

“On the global scale, greenhouse gases like carbon dioxide cause the most concern related to climate change,” said Yun Qian, the paper’s lead author and an atmospheric scientist at PNNL. “But our research shows that in some places like the Tibetan Plateau, soot can do more damage.”

Roof of the Earth

Qian and his colleagues focused their research on the Tibetan Plateau, a giant outcropping of land between China and India that’s nicknamed the “Roof of the Earth.” About five times the size of Texas and as much as 5 miles high in places, the Tibetan Plateau greatly influences the Asia’s weather, including the annual deluge of rain and strong winds that come with monsoons. It’s also home to the largest volume of ice outside of the north and south poles. Glaciers and snow on the plateau grow and melt as seasons change, providing runoff that feeds most of the region’s major rivers, including the Yangtze in China and the Ganges in India.

Soot has increasingly dirtied the Tibetan Plateau’s winter-white surfaces in the past two decades. A byproduct of the region’s rapid growth in industry and agriculture, soot leaves smokestacks and burning fields in developing Asian countries before it floats into the sky, where winds carry it toward the plateau. Soot is dark and absorbs far more heat from sunlight than pristine white snow. Soot’s ability to soak up more solar rays causes the snow it lands on to melt faster. The Tibetan Plateau also receives more direct sunlight than the distant north and south poles, meaning soot’s snow-melting powers are be more pronounced on the plateau.

To find out how much soot is affecting the Tibetan Plateau’s region, Qian and colleagues used a global climate computer model, the Community Atmosphere Model. The model allowed them to examine a mixture of possible scenarios, including if soot sat on the Tibetan Plateau’s snow, if soot was floating in the air above the plateau and if increased carbon dioxide was in the air as a result of industrialization.

More heat, melting

The model’s calculations showed that the average air temperature immediately above the plateau increased when all the scenarios were combined. Alone, both soot on snow and carbon dioxide increased temperatures about 2 degrees Fahrenheit. But while carbon dioxide increased temperatures fairly evenly throughout the region, including the ocean, soot on snow only significantly heated up the Tibetan Plateau and north Asia. Researchers concluded that soot on snow can increase the temperature differences between air over land and air over the ocean, which drive monsoons.

Soot on snow also stood out when the model investigated water runoff. Smaller changes were observed when just carbon dioxide or soot in the air were examined, but soot on snow by itself increased runoff substantially during the late winter and early spring and then decreased it during the late spring and early summer. With all three scenarios combined, the runoff increased by 0.44 millimeters (or nearly two-one hundredths of an inch) daily between February and April and then decreased by 0.57 millimeters daily between May and July. These changes provide more water in the winter, when it’s not particularly useful to farmers, but less in the summer when it’s needed to grow crops.

The researchers reasoned that soot on snow is more efficient in melting the plateau’s snowpack because of its close proximity to the snow. Like a warm blanket covering the plateau, soot on snow can almost immediately warm and melt the snow beneath it. But carbon dioxide and soot in the atmosphere have to transfer the heat they absorb way down to the plateau below, with some heat inevitably being lost.

Nature’s heat pump

Before this research, scientists knew that the Tibetan Plateau acted like a natural heat pump for the region’s weather. The plateau reaches 5 miles high in some places, allowing the air above it to be warmer than other air at the same elevation. The warm air strengthens air circulation around the plateau and causes the iconic, drenching monsoons that move through the region every year.

But with soot on snow causing more snowmelt on the plateau, the plateau is increasingly bare. Less snow covering to reflect solar heat means the Tibetan Plateau is absorbing more sunlight, which the researchers hypothesized was causing the atmosphere above the plateau to warm up even more. They used climate models to find out of this affects the area’s monsoons.

Stronger monsoons

The surface temperature above the plateau increased by more than 2 degrees Fahrenheit in May due to soot on snow alone. The researchers found that this warmer air above the plateau rises and air is drawn from India to replace it. In turn, moist air hanging above Arabian Sea and Indian Ocean blows in over India. Known as the South Asian Monsoon system, this southwest-northeast flow also brings in more soot from India to the Tibetan Plateau that perpetuates the cycle. As a result, the researchers found that the South Asian Monsoon system is starting earlier and bringing more rain to central and Northern India in May than it would without soot on the plateau’s snow.

The soot-on-snow effect lingers throughout the summer and causes another weather shift in the East Asian Monsoon system over China. By July, much of the plateau’s snow has already melted. The plateau’s bare soil is warmer and further heats the plateau’s air. Coupled with cool ocean air nearby, the plateau’s heat strengthens the East Asian Monsoon. The models showed that rain increases 1 to 3 millimeters per day over southern China and the South China Sea. The strengthened monsoon advances to northern China, which also receives more rain than it would otherwise, while the rains mostly skip central East China, including the Yangtze River Basin.

More work needs to be done to refine these findings, however. Qian and his co-authors noted that existing global climate models don’t allow for the close-up, detailed resolution needed to accurately portray the Tibetan Plateau’s many varying peaks. The model’s coarse resolution likely resulted in the plateaus’ snowpack being overestimated, meaning the researchers’ results represent the maximum amount that soot on snow could potentially impact hydrological and weather systems in the region.

Future research could also factor in dust, which blows throughout Asia with the wind. While soot is believed to have a larger impact on snowmelt than dust per unit mass, the region likely has more total dust than soot. However, dust is more challenging to represent in models, since its sources can’t be as easily measured as the polluting smokestacks and burning fields that cause soot.

“The Tibetan Plateau is an amazing, dynamic place where many things come together to develop large climate systems,” Qian said. “Our research indicates that soot on snow can be a large player in the region’s climate, but it’s not the only factor. Many other elements need to be studies before we can say for sure what is the leading cause of snowmelt – which also contributes to retreating glaciers – on the plateau.”

Satellites provide up-to-date information on snow cover

This image of Trans-Labrador Highway, located in Canada's province of Newfoundland and Labrador, shows a heavy excavator bucket and a snow plow clearing snow from the road. - Credits: A. Khan, Goverment of Newfoundland and Labrador
This image of Trans-Labrador Highway, located in Canada’s province of Newfoundland and Labrador, shows a heavy excavator bucket and a snow plow clearing snow from the road. – Credits: A. Khan, Goverment of Newfoundland and Labrador

ESA GlobSnow project led by the Finnish Meteorological Institute uses satellites to produce up-to-date information on global snow cover. The new database gives fresh information on the snow situation right after a snowfall. Gathering this information was not possible before when only land-based observations were available.

European Space Agency┬┤s (ESA) GlobSnow project, led by the Finnish Meteorological Institute, can map the extent and volume of snow cover especially on the northern hemisphere. Launched at the beginning of November, the service provides almost real-time data on snow cover and snow depth. The purpose of this service, accessed through the GlobSnow website maintained by the Institute, is to create a global database containing the snow data gathered by satellites.

Global data on snow cover

Snowfall impedes transport but also causes floods in many countries. The seasons affect snow cover the most on the northern hemisphere. The average snow cover in winter extends over an area of 20-40 million square kilometres; in other words, the snow contains as much water as one billion Olympic swimming pools. At the same time, the snow cover is one of the most important factors affecting the global climate, meteorology and water systems. Long distances between observation stations, especially in the sparsely-populated regions of Eurasia and North America, have made it difficult to chart snow and its volume at global level.

More accurate climate models

The data produced by satellites are used in the forecasting of floods and in climate research. In the coming year, many countries will test application of the new material for making hydrological models and flood forecasts. GlobSnow also provides climate researchers with snow data extending over the past 30 years. Access to satellite data enables researchers to monitor and analyse climatic trends. It has been discovered, for instance, that the snow cover has shrunk globally; this is one indicator of climate change. The database also provides increasingly accurate input data for climate models, thereby further improving the quality and accuracy of climate models.

Low-cost temperature sensors, tennis balls to monitor mountain snowpack

UW assistant professor Jessica Lundquist (left) and graduate student Eset Alemu flake nylon rope into a bag so it will unravel smoothly when a sensor is catapulted into the canopy. -  University of Washington
UW assistant professor Jessica Lundquist (left) and graduate student Eset Alemu flake nylon rope into a bag so it will unravel smoothly when a sensor is catapulted into the canopy. – University of Washington

Fictional secret agent Angus MacGyver knew that tough situations demand ingenuity. Jessica Lundquist takes a similar approach to studying snowfall. The University of Washington assistant professor of civil and environmental engineering uses dime-sized temperature sensors, first developed for the refrigerated food industry, and tennis balls. In summer months she attaches the sensors to tennis balls that are weighted with gravel, and uses a dog-ball launcher to propel the devices high into alpine trees where they will record winter temperatures.

This isn’t TV spy work – it’s science. Lundquist studies mountain precipitation to learn how changes in snowfall and snowmelt will affect the communities and environments at lower elevations. If the air temperature is above 32 degrees Fahrenheit the precipitation will fall as rain, but if it’s below freezing, it will be snow.

“It’s fun, like backyard science,” Lundquist said of her sensors, which were originally designed to record temperature of frozen foods in transit. She began adapting the devices for environmental science while a postdoctoral researcher in Colorado and has refined them over the years. “It turns out they work phenomenally well.”

Last year the American Geophysical Union awarded Lundquist its Cryosphere Young Investigators Award for her fieldwork. This week at the AGU’s fall meeting in San Francisco she will present her low-cost temperature-sensing technology and some current applications.

Scientific weather stations typically cost about $10,000. Lundquist’s system measures and records the temperature every hour for up to 11 months in remote locations for just $30 apiece. Another advantage is that they are easily deployed in rough terrain.

Her temperature sensors are a fun approach to studying a serious problem. One quarter of the Earth’s continents have mountainous terrain, Lundquist said, and mountain rivers provide water for 40 percent of the world’s population. Those mountain rivers are largely fed by snowmelt. But if winters become warmer due to climate change, the snow line is expected to inch up the mountainside, and snow is expected to melt earlier in the springtime.

“Mountains are the water towers of the world,” Lundquist said. “We essentially use the snow as an extra reservoir. And you want that reservoir to hold the snow for as long as possible

Her sensors are being used to improve computer models in areas where water managers want to know exactly where snow is accumulating and on what date it starts to melt.

“People typically assume that temperature decreases with elevation,” Lundquist says. But actual mountain temperatures depend on the vegetation, slope and variable weather. “If you have a management decision, there’s a specific place you have to make a decision for.”

If more rain falls instead of snow, it will increase the risk of flooding during storms. Lundquist’s sensors are currently being used by the California-Nevada River Forecasting Center as part of a project pinpointing at what elevation snow turns to rain, to improve storm flooding forecasts. As part of that project, UW graduate students are placing her sensors in river canyons that are too steep for traditional weather stations.

She is also deploying sensors in Yosemite National Park to see if earlier snowmelt may cause earlier drying of streambeds and affect vegetation growth in the Tuolumne Meadows. Her sensors there provide ground verification of satellite measurements.

The City of Seattle is also using Lundquist’s sensors to study how different restoration approaches for trees in the Cedar River watershed, which supplies water to the city, affect snow retention.

“I have a lot of fun deploying my sensors because I love being in the mountains,” Lundquist said. “They also sense conditions in these remote environments that we can’t know about any other way.

Measuring snow with a bucket, a windmill, and the sun?

In Maine, government scientists have figured out how to measure snowfall in remote areas with a bucket, a small windmill, and the sun – all the while saving money, energy, and, ultimately helping to save lives.

What led to this energy-efficient ingenuity was the need to help the National Weather Service forecast and predict the risk of floods from spring snowmelt.

The problem was this: While the USGS has about 15 snowmelt measurement sites in Maine, they also needed a way to measure snowfall in remote areas where power grids are scarce. Emergency managers need accurate information to prepare for forthcoming hazards and energy companies need to plan ahead for how much water to expect in reservoirs.

“We needed to find an alternative power source,” said Bob Lent, chief of the USGS Maine Water Science Center in Augusta. “So we cobbled together a small-scale commercial windmill to replace commercial AC power, and supplemented the windmill with solar panels. What we ended up with is a windmill that powers our measurements on windy and cloudy days, and solar panels that power them on calm, sunny days,” said Lent. “And,” he added, “not only will we get more accurate information, but the systems will pay for themselves in about 3 to 4 years since using the electricity-dependent devices cost between $200 and $400 a year.”

A prototype system has been housed in use at the USGS office in Augusta for the past winter. It has proved so accurate, said Lent, that the USGS plans to install four snowfall sites around the state this summer using the same system.

Basically, the system looks like this: a gage is attached to a 5-gallon bucket that sits atop a simple wooden platform on a metal pole. The gage has a heating element to melt the snow as it collects in the cone of the bucket. The gage only turns on when snow is detected. Nearby is a data-collection box that is linked to the windmill and solar panels. When the bucket fills up with melted snow it tips over and empties. Each tip of the bucket measures 0.01 inches of precipitation and is recorded to the data recorder, which transmits the data and is updated on the web every hour.

“We are very optimistic about the utility of this system in other remote areas in the country and not just for snowfall measurements. It would be good for any remote site that needs more power than solar alone can deliver. For example, this could be used to measure water quality in the swamps of Florida as well as snowfall in Maine,” Lent noted.

“It’s a very small step in a very long journey of helping this country become greener, but this embodies what we need to be doing and the direction in which we need to be going,” said Lent.

Satellites search out South Pole snowfields

As skiers across the world pay close attention to the state of the snow on the slopes, there are a different group of scientific snow-watchers looking closely at a South Pole snowfield this January.

Scientists from around the world coordinated by the UK’s National Physical Laboratory (NPL) are examining an Antarctic snowfield this January as part of the world’s largest inter-comparison between satellite sensors.

The results will allow scientists to fully quantify differences between the measurements made by the satellite instruments in orbit. This will lead to improvements in their calibration and ensure that the data collected is all quality assured. This will ultimately result in more confidence in the data used for climate change, weather systems and monitoring disaster areas. Some of these measurements require the detection of changes of a few tenths of a percent per decade, yet current sensors exhibit biases between themselves of many percent, often more than 20 times this level.

Over 30 sensors from space agencies across the globe, including several from the UK, ranging in spatial resolution from a metre to several hundred metres will measure the reflectance of the sun by the Antarctic snow. All of the data will be cross-compared to each other supported by ground measurements of the site.

The measurements will be taken over a snowfield in Antarctica known as ‘DOME C’. These can only be performed in December and January when the Sun is relatively high in the sky during the southern hemisphere summer.

Nigel Fox, head of Earth Observation in NPL’s Optical Technologies software and computing team said:

“This is the most comprehensive comparison of its kind ever organised and is a direct result of efforts led by NPL to establish improved quality assurance of Earth observation data. As the data from many of the sensors involved in this comparison is used in studies of climate change, it is essential that we can reliably combine it together and start to use it as a truly global resource and reference for the future. This comparison will provide the information and evidence to allow this to happen”

This comparison is the first of a series led by NPL, supported by the Department for Innovation, Universities and Skills, the European Space Agency and the British National Space Centre, to address key issues in Earth Observation on behalf of the worlds Earth Observation community. Future ones include measurements of the temperature of the ocean and reflectance of a salt lake in Turkey.

Looking to the future, it is hoped that the UK can continue to take a lead in this niche but crucial role to underpin the calibration and validation of Earth Observation satellites. One example is the development of a “calibration satellite” in space to ensure the accuracy of satellites in orbit.

Dirty snow causes early runoff in Cascades, Rockies

When soot from pollution settles on pristine snow, it can increase snowmelt in the winter month of February (top left, red) and decrease it in the late spring (May -- bottom right, blue). -  Pacific Northwest National Laboratory
When soot from pollution settles on pristine snow, it can increase snowmelt in the winter month of February (top left, red) and decrease it in the late spring (May — bottom right, blue). – Pacific Northwest National Laboratory

Soot from pollution causes winter snowpacks to warm, shrink and warm some more. This continuous cycle sends snowmelt streaming down mountains as much as a month early, a new study finds. How pollution affects a mountain range’s natural water reservoirs is important for water resource managers in the western United States and Canada who plan for hydroelectricity generation, fisheries and farming.

Scientists at the Department of Energy’s Pacific Northwest National Laboratory conducted the first-ever study of soot on snow in the western states at a scale that predicted impacts along mountain ranges. They found that soot warms up the snow and the air above it by up to 1.2 degrees Fahrenheit, causing snow to melt.

“If we can project the future — how much water we’ll be getting from the rivers and when — then we can better plan for its many uses,” said atmospheric scientist Yun Qian. “Snowmelt can be up to 75 percent of the water supply, in some regions. These changes can affect the water supply, as well as aggravate winter flooding and summer droughts.”

The soot-snow cycle starts when soot, a byproduct of burning fossil fuels, darkens snow it lands upon, which then absorbs more of the sun’s energy than clean white snow. The resulting thinner snowpack reflects less sunlight back into the atmosphere and further warms the area, continuing the snowmelt cycle.

This study revealed regional changes to the snowpack caused by soot, whereas other studies looked at the uniform changes brought by higher air temperatures due to greenhouse gases.

Previous studies have examined the effect of airborne or snowbound soot on global climate and temperatures. Qian and his colleagues at PNNL used a climate computer model to zoom in on the Rocky Mountain, Cascade, and other western United States mountain ranges. They modeled how soot from diesel engines, power plants and other sources affected snowpacks it landed on.

They found that changes to snow’s brightness results in its melting weeks earlier in spring than with pristine snow. In addition, less mountain snow going into late spring means reduced runoff in late spring and summer. They will report their findings in an upcoming issue of the Journal of Geophysical Research — Atmospheres.

Making Snowhills from Mountains

Researchers know that soot settles on snow. And like an asphalt street compared to a concrete sidewalk, dirty snow retains more heat from the sun than bright white snow. Qian and colleagues wanted to determine to what degree dark snow contributes to the declining snowpack.

To get the kind of detail from their computer model that they needed, the PNNL team used a regional model called the Weather Research and Forecasting model — or WRF, developed in part at the National Center for Atmospheric Research in Boulder, Colo. Compared to planet-scale models that can distinguish land features 200 kilometers apart, this computer model zooms in on the landscape, increasing resolution to 15 kilometers. At 15 kilometers, features such as mountain ranges and soot deposition are better defined.

Recently, PNNL researchers added a software component to WRF that models the chemistry of tiny atmospheric particles called aerosols and their interaction with clouds and sunlight. Using the WRF-chem model, the team first examined how much soot in the form of so-called black carbon would land on snow in the Sierra Nevada, Cascade and Rocky Mountains.

Then the team simulated how that soot would affect the snow’s brightness throughout the year. Finally, they translated the brightness into snow accumulation and melting over time.

Gray Outlook

“Earlier studies didn’t talk about snowpack changes due to soot for two reasons,” said atmospheric scientist and co-author William Gustafson. “Soot hasn’t been widely measured in snowpack, and it’s hard to accurately simulate snowpack in global models. The Cascades have lost 60 percent of their snowpack since the 1950s, most of that due to rising temperatures. We wanted to see if we could quantify the impact of soot.”

Their simulations compared well to data collected on snowpack distribution and water runoff. But their first experiment did not include all sources of soot, so they modeled what would happen if enough soot landed on snow to double the loss of brightness. In this computer simulation, the regional climate and snowpack changed significantly, and not in a simply predictable way.

Overall, doubling the dimming of the snow did not lead to twice as high temperature changes — it led to an approximate 50 percent increase in the snow surface temperature. The drop in snow accumulation, however, more than doubled in some areas. Snowpack over the central Rockies and southern Alberta, for example, dropped two to 50 millimeters over the mountains during late spring and early winter. The most drastic changes occurred in March, the model showed.

The team also found that soot decreased snow’s brightness in two ways. About half of soot’s effect came from its dark color. The other half came indirectly from reducing the size of the snowpack, exposing the underlying darker earth.

Studies like this one start to unmask pollution’s role in the changing climate. While greenhouse gases work unseen, soot bares its dark nature, with a cloak that slowly steals summertime’s snow.