Monthly Highlights

All About Arctic Climatology and Meteorology

Laura Naranjo — Tue, 30 Apr 2013 20:45:16 +0000

The Arctic is often referred to as the Earth’s icebox, helping cool the globe’s ocean currents and shaping the jet stream. Similarly, warming in the Arctic influences conditions elsewhere on the planet. This means what happens in the Arctic doesn’t stay in the Arctic. NSIDC’s educational Web site, All About Arctic Climatology and Meteorology, helps explain the how region plays a role in weather and climate across the Northern Hemisphere.

Ripples from the Arctic

This aurora appeared over the city of Iqaluit in Canada’s Nunavut Territory. High-altitude oxygen, about 200 kilometers (124 miles) up, produces rare, all-red auroras, while lower-altitude oxygen, about 60 kilometers (37 miles) up, is the source of the most common auroral color, a bright yellow-green. Blue light comes from ionized nitrogen molecules. The nitrogens also create purplish-red and red colors in the aurora.
Credit: Flickr/ascappatura

In the Arctic, the usual meteorological conditions factor into the region’s weather: wind, humidity, temperature, clouds, precipitation, air pressure, and more. But the Arctic’s unique geography and high latitude also foster longer-term weather patterns, which recur regularly, even yearly. All About Climatology and Meteorology describes and illustrates these patterns, including cyclones and polar lows. One major pattern that scientists are always tracking is the Arctic Oscillation. Different phases of this oscillation carry consequences across the Northern Hemisphere, either causing warm and dry winters or blasting unusually cold and wet weather across Europe, China, and parts of the United States.

Readers can also learn about interesting and unique local phenomena caused by the Arctic’s icy surfaces and special atmospheric conditions, including ice blink, fog bows, and of course, the famous Aurora Borealis. Early polar navigators sometimes relied on these optical illusions to determine whether open water or sea ice lay ahead. At other times these illusions deceived explorers into turning back, sailing away from mirages that made open water look like towering mountains.

New updates to a popular site

The left side of this illustration shows effects of the positive phase of the Arctic Oscillation, while the right side shows the effects of the negative phase of the Arctic Oscillation. Both phases influence weather patterns further south in Europe, China, and the United States. Credit: J. Wallace, University of Washington

All About Arctic Climatology and Meteorology is one of NSIDC’s most popular sites, consistently ranking among our top ten pages. The content was originally derived from a CD released in 2000, the Primer for Newcomers to the North, part of the Environmental Working Group’s Arctic Atlases. NSIDC recently updated the site with new information, additional photographs and images, and sections about climate change, exploration, and Arctic peoples.

To read more, visit the updated and expanded All About Arctic Climatology and Meteorology site. Learn how the Arctic keeps its cool, and how changes in the Arctic produce far-reaching effects around the globe. Read about how the Arctic was discovered and explored, how people now survive life in the Arctic, and how scientists conduct research in such an icy and inhospitable region. In addition, the site also includes a gallery of new and historic photographs of the Arctic.

Visit All About Arctic Climatology and Meteorology in About the Cryosphere, or go to the Web site directly at http://nsidc.org/cryosphere/arctic-meteorology/index.html.

Glimpses of sea ice past

Natasha Vizcarra — Thu, 18 Apr 2013 15:47:12 +0000

Recently, the National Snow and Ice Data Center acquired stacks of 49-year-old film rolls from a National Climate Data Center storage facility in North Carolina. “There were fifty cardboard boxes. Each contained ten rusty, dusty canisters, each containing 500 feet of 35-millimeter negative film,” said NSIDC technical services manager Dave Gallaher. “We really wanted these.”

NSIDC scientist Walt Meier, who studies the yearly waxing and waning of sea ice in the Arctic, said the old film from one of the first U.S. Earth-observing missions, the Nimbus 1 satellite, could give scientists a deeper look back at climate. It happened that the dusty boxes of old film were dated August to September 1964. “This film contains basically the earliest satellite data we have of Arctic and Antarctic sea ice extent,” Meier said. But making those canisters of film talk would be no easy task.

Right place, right time

National Snow and Ice Data Center acquires dozens of canisters of 35-millimeter film that contain images of the 1964 Arctic sea ice minimum and the Antarctic maximum. The images were collected by the Nimbus 1 satellite, which circled the globe from August 28, 1964 to September 23, 1964. Credit: NSIDC

Scientists pay close attention to the ice in September, when it shrinks to its minimum extent. Arctic sea ice has long been recognized as a sensitive climate indicator, and has undergone a dramatic decline over the past thirty years. They currently depend on a satellite record that begins in 1979.

Nimbus 1 was a test of weather satellite technology, including a video camera, so scientists could improve weather forecasts. Data specialist Garrett Campbell at NSIDC, “There were no fancy satellite sensors in 1964,” he said. “Scientists strapped a video camera to the Nimbus 1 satellite, sent it into orbit, and hoped for the best.”

As it circled the globe in August and September, Nimbus 1 transmitted still shots of the Earth to a television monitor, which researchers photographed. After using the stills for weather forecasting research, scientists archived them in a secure storage facility.

In 2009, Gallaher stumbled on a NASA conference poster about the recovery of the film, and realized that it would have captured images of the Arctic sea ice minimum and the Antarctic maximum in 1964. Satellite records of Arctic sea ice extent only went as far back as 1978. There were other observations before 1978, like ice charts from naval ships, radiometer records, and other satellite imagery. None of these gave scientists a full view of the Northern Hemisphere. But the old film would. So Gallaher teamed with Meier and NASA to try to recover any information the old films might contain.

Arctic and Antarctic sea ice, 1964

A single frame image of the Arctic ice edge north of Russia near Franz Josef Land (centered at 78 degrees North and 54 degrees East) on September 4, 1964, after processing by the National Snow and Ice Data Center. The estimated boundary between the ice and ocean is marked by red hash tags; openings, or leads, within the ice are marked by blue hash tags. Credit: NSIDC

Campbell, who spent the past two years examining shots from the film rolls, said the images would have been too overwhelming for researchers to process in the 1960s. “We didn’t have the computing power to handle all those images at that time,” Campbell said. “In 1964, researchers would have had to develop every single frame as a photograph and lay it out on the floor of a large room.” To get a good view of this composite of thousands of photographs, one would have to be standing a few floors above the photograph-covered floor, ideally on a very tall ladder.

But with today’s technology, Campbell simply worked with two undergraduate students to scan close to 40,000 frames, made sure the images had the right latitude and longitude, and stitched the photos together in his computer. With those images, Campbell produced the first satellite maps of the sea ice edge in 1964 and an estimate of September sea ice extent for both the Arctic and the Antarctic. According to the data, September Antarctic sea ice extent measured about 19.7 million square kilometers. “That’s higher than any year observed from 1972 to 2012,” Meier said.

Figuring out the sea ice extent for the Arctic was more challenging. It was harder for the team to distinguish the ice edge along the coasts from snow or glacier-covered islands in the Canadian Archipelago. Also, there were not many images of Alaska and eastern Siberia to work from, so Campbell relied on old Russian and Alaskan ice charts. His analysis yielded a September 1964 Arctic sea ice extent of 6.90 million square kilometers. “The 1964 estimate is reasonably consistent with 1979 to 2000 conditions,” Meier said. “It suggests that September extent in the Arctic may have been generally stable through the 1960s and the early 1970s.”

NSIDC will be making these images, as well as high-resolution infrared data from the Nimbus 1 satellite, available to researchers beginning May 2013. The team has also acquired satellite imagery from Nimbus 2 and 3, and other satellites operating in the late 1960s and early 1970s. The result, hopefully, is a longer record of sea ice that Meier said would “put the dramatic decline of Arctic summer sea ice extent in a longer-term context” and prove useful to other scientists studying today’s changing climate.

The National Snow and Ice Data Center scanned close to 40,000 images from Nimbus 1 satellite data to produce the earliest satellite images of Arctic and Antarctic satellite extent. The left image is a composite of the Arctic and the right image is a composite of the Antarctic. Credit: NSIDC

Reference

Meier, W. N., Gallaher, D., and G. C. Campbell. 2013. New estimates of Arctic and Antarctic sea ice extent during September 1964 from recovered Nimbus I satellite imagery. The Cryosphere, 7, 699–705, doi:10.5194/tc-7-699-2013.

Austin Post Glacier Photographs

Jane Beitler — Thu, 14 Mar 2013 17:08:54 +0000

“I have often claimed this collection to be more valuable than the moon rocks – after all, we can go back to the moon for more rocks, but we can not go back to take pictures of glaciers 30 years ago.” —Robert Krimmel, United States Geological Survey.

This aerial photograph of Douglas Glacier, Washington State, USA was taken by Austin Post on September 27, 1960. Access the full-resolution photograph via the NSIDC Glacier Photograph Collection.

Credit: Austin Post, NSIDC Glacier Photograph Collection

From above, glaciers look like rivers of ice. Like rivers, but much more slowly, they flow downhill, are replenished by precipitation, and diminished by melting. On balance, they ought to stay about the same, but glaciers are sensitive to changes in climate. Telltales of larger climate changes, they shrink in a warming climate or grow in a cooling climate.

Only fairly recently have satellites been used to monitor glaciers on a global scale by tracking changes in area, length, elevation, and velocity. Before satellites and still today, scientists with cameras documented the state of a glacier so that they could study whether it is growing or shrinking, advancing or retreating.

A massive problem

Photographing glaciers on foot by hiking to the terminus with a camera could only capture a small number of glaciers, because it is time consuming. With the world’s glaciers uncounted (NSIDC’s World Glacier Inventory contains records of 130,000 glaciers, but scientists think there are many more), Alaska alone may have as many as 50,000 glaciers, but only about 500 of them are named. So before space-based remote sensing became prevalent, glaciologists used aerial photography to study glaciers in their remote, hostile environments.

Austin Post remained fascinated with glaciers and glacier photography to the end of his life.

Credit: Bruce Molnia, USGS

Some visionary glaciologists with airplanes and cameras captured important records of glaciers, starting in the 1930s. As part of a United States Geological Survey (USGS) program for more than 35 years, photographer and glaciologist Austin Post (1922-2012) sometimes lugged his large-format camera weighing more than 60 pounds up mountain trails to photograph glaciers. But more often, he flew in small aircraft over mountain wildernesses, wrangling several cameras as he shot through cutouts in the aircraft floor and sides. Post, who started as a support technician on glacier projects, was passionately interested in glaciers and eventually earned the title of research scientist, despite lacking a college degree. He became an expert observer of glaciers as well as highly skilled in capturing them from vertical and oblique angles. As pioneering glaciologist William O. Field noted, “Not only does Austin know glaciers and appreciate what features should be photographed, and how and to what detail, but also he is a good observer.”

Starting in the 1960s Post photographed glaciers in Alaska, Canada, Greenland, and the western U.S., leaving an irreplaceable legacy of documentation regarding glaciers and changes in Earth’s climate.

Captured and on display

This aerial photograph of Nisqually Glacier, Washington State, USA was taken by Austin Post on September 21, 1960. Access the full-resolution photograph via the NSIDC Glacier Photograph Collection.

Credit: Austin Post, NSIDC Glacier Photograph Collection

The USGS collected these aerial photographs over the years, but at first they were inaccessible to most researchers. Starting in 1978, NSIDC (then called the World Data Center for Glaciology-A) helped create metadata describing the photographs, and created a database of the metadata, as well as copies of the photographs on microfilm. In 2008, these images began to be digitized under the National Oceanic and Atmospheric Administration (NOAA) Climate Database Modernization Project, and added to the NSIDC Glacier Photograph Collection online. NSIDC is currently creating metadata for the digitized images and adding them to the online collection as time and funding permit. Today more than 14,000 images are online, including over 6,400 photographs by Post. Researchers and the public can search for and download images using NSIDC’s Web site. Work continues to make the entire collection accessible online. NSIDC has more than 100,000 Austin Post glacier photographs in its archives, as well as many other photographs waiting to be added.

The Austin Post photographs and the NSIDC Glacier Photograph Collection were developed with the support of USGS and NOAA. Today, however, these resources are in need of ongoing stewardship of the physical materials, as well as resources to continue their digitization and metadata to enable online discovery and access. As climate records, their value continues indefinitely as a record of past climate and are used by researchers to compare glaciers then and now, and by educators and communicators to help everyday people see how most of the world’s glaciers are changing. We may not be able to stop many glaciers from disappearing, but we can work to keep these valuable observational records intact and accessible for future research.

More information

Adopt a Glacier

NSIDC Archives

NSIDC Glacier Photograph Collection

Scurlock, John. 2007. Austin Post: Legendary chronicler of glaciers. Northwest Mountaineering Journal 4.

Greenland Ice Sheet Today

Laura Naranjo — Thu, 31 Jan 2013 16:47:45 +0000

A large stream of meltwater, about 5 to 10 meters wide, emerges from an upstream supraglacial lake in the Greenlandic ice. This photograph was taken during the summer of 2012, when a record 97 percent of the ice sheet surface experienced melting. Photo credit: M. Tedesco/CCNY

Greenland is home to the largest ice sheet outside of Antarctica, and scientists are discovering that its ice is not immune to temperatures that continue to rise across the Arctic. While scientists do not expect a rapid or sudden thawing, a recent burst of surface melt revealed just how vulnerable Greenland’s ice may be.

During the summer of 2012, nearly 97 percent of the ice sheet’s surface melted, the most extreme melt extent scientists had seen in three decades of satellite records. This stood in contrast to the 40 to 50 percent surface melt that typically occurs during the summer. Although scientists were able to blame the extreme melt on an unusually warm mass of air that parked over Greenland for several weeks, this event occurred as the Arctic sea ice extent was declining to what would become a record low later in the year. Consequently, scientists are paying closer attention to the Greenland Ice Sheet and its potential for melting and contributing to even small amounts of sea level rise.

Watching the ice

Greenland Ice Sheet Today will feature data-based melt images of the ice sheet, updated daily with a one-day lag. Credit: NSIDC/Thomas Mote, University of Georgia

The extreme summer melt of 2012 caught many by surprise, and prompted NSIDC to develop a new Web site to help track Greenland’s ice. This site, Greenland Ice Sheet Today, features daily melt images and images showing cumulative melt days on the ice sheet. Both images are updated daily, with a one-day lag. A daily graph will chart the current melt percentage against the average melt observed in the satellite record.

NSIDC partnered with two experts to help develop the site: Dr. Thomas Mote of University of Georgia and Dr. Marco Tedesco of the City University of New York. They both provide expertise on the Greenland Ice Sheet, and Dr. Mote will supply imagery derived from NSIDC’s passive microwave brightness temperature data.

NSIDC will post regular updates describing conditions in Greenland and provide analysis placing them in the larger historical context, as well as in the context of Arctic-wide conditions.

Ice in the balance

Although the Greenland Ice sheet undergoes seasonal melting each summer, surface melt during July 2012 reached record levels. Runoff from the ice sheet flooded the Watson River and swept away parts of a bridge in the town of Kangerlussuaq. The left image is from May 31, 2012, prior to the melt. The right image is from July 25, 2012, after the record surface melt. Credit: NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using Advanced Land Imager data from the NASA EO-1 team.

All across the Arctic, warming oceans and declining sea ice are leaving tidewater glaciers vulnerable to melting, and making many of Greenland’s outlet glaciers more likely to retreat. And further inland, higher air temperatures may be thawing interior ice more rapidly. Greenland’s ice has begun to feature more melt ponds, rivers, and other melt water features that drain increasing amounts of water from the ice sheet.

Melting on the Greenland Ice Sheet continue to mirror changes happening in the larger Arctic environment. “If you look at years where we’ve had minimum sea ice extent, like 2007 and 2012 for example, those are often years in which we’ve seen extensive melting over Greenland,” Mote said. “There are certainly similarities between what we’re seeing in Greenland and what we’re seeing in other parts of the Arctic.”

While the changes in Greenland may not yet be as dramatic as those in other regions, scientists are concerned that more melting on the ice sheet could pump massive amounts of freshwater into the oceans. In addition to raising sea levels, a large influx of water could reduce salinity in parts of the ocean and potentially alter ocean currents.

The images and analysis featured in Greenland Ice Sheet Today provide a new way to monitor conditions in and around Greenland. The site complements NSIDC’s Arctic Sea News and Analysis Web site and will help pinpoint changes and emerging patterns around the Arctic in near-real time. Mote said, “I think we’re still trying to get a sense of just how inter-related these different cryospheric measures are across the Arctic.” Greenland Ice Sheet Today will be another tool to help users see how changes across the Northern Hemisphere may be influencing Greenland’s ice.

Greenland Ice Sheet Today

Reference

Nghiem, S. V., D. K. Hall, T. L. Mote, M. Tedesco, M. R. Albert, K. Keegan, C. A. Shuman, N. E. DiGirolamo, and G. Neumann. 2012. The extreme melt across the Greenland ice sheet in 2012. Geophysical Research Letters, 39(20), doi:10.1029/2012GL053611

A windy dilemma

Agnieszka Gautier — Thu, 20 Dec 2012 17:45:32 +0000

Distribution of glaze regions (cyan) in East Antarctica, showing the major drainage basins for the ice sheet. The 1,500 to 2,500 meter elevation contours are shown in dark blue. Drainage basins are labeled with abbreviations of local major features or research bases. Credit: Ted Scambos et al., Journal of Glaciology

On the world’s most massive ice sheet, the bitter wind sculpts the surface snow into long, low dunes that are barely detectable while staring out into the horizon. Between the dunes, katabatic winds, caused by dense, cold air sinking and flowing off the continent, polish wind-swept areas to a high glaze. Much like waves on the ocean, megadunes form against the wind with scavenged snow rising only a few meters high but running tens of miles long and up to two miles wide.

NSIDC lead scientist Ted Scambos has studied these formations for more than a decade. “Wind-glaze regions represent near-permanent bare patches in the snow layer—instead of a blanket layer, it’s more like Swiss cheese,” Scambos said. “Count the holes in the Swiss cheese and the overall accumulation of snow is much less than most modern scientists are saying.” Knowledge of Antarctica’s snow precipitation informs its contribution to seal level and is measured by the surface mass balance (SMB), or the difference between accumulation and ablation (sublimation and melting). A negative SMB implies a retreating ice sheet. So Scambos, along with a team of scientists from around the world, used a combination of satellite remote sensing and field-gathered datasets to map the extent of wind glaze in the East Antarctic Ice Sheet (EAIS) plateau.

Formation of wind glaze

The EAIS, much bigger than its western-hemisphere counterpart, features a distinctive topography of megadunes and wind-glaze surfaces, sculpted by the intense climate of the region. Low temperatures and low snow-accumulation, coupled with near-continuous katabatic winds, create wind-glazed surfaces that can be 2 to 200 square kilometers (1 to 77 square miles) in area, usually above 1,500 meters (4,920 feet) on the leeward slopes of megadunes.

The wind-glaze surfaces result from strong winds, driven by the continent’s temperature inversions. Typically the air closer to the Earth is warmer because the sun radiates warmth off the Earth’s surface. Due to Antarctica’s thick ice sheet, with an average thickness of 2,012 meters (6,600 feet), the coldest, most dense air hovers on the surface, providing the impetus for Antarctica’s notoriously strong winds that sweep out toward its coastlines. With higher elevations, the gravity-driven drainage of cold inversion air accelerates the flow, removing any precipitated or wind-deposited snow within wind-glaze regions.

Wind gives a snowstorm personality. Under seemingly choreographed gusts, snow appears to merely resettle. Prior studies have assumed the same: wind distribution of snow is a mass-conservative process, meaning that mass lost from windswept areas is deposited in adjacent areas. But on the EAIS plateau, adjacent high-accumulation regions do not compensate for the surface loss. Since air must compress to descend, the snow it carries down a mountainside gets progressively drier, smaller in particle size and more dissolvable.

An in-depth look

Ted Scambos checks on the GPS/GPR surveying system during the 2002-03 Megadunes expedition. Credit: Ted Scambos and Rob Bauer, NSIDC

Beneath wind-glaze surfaces, a porous firn layer, 50 to 70 meters (164 to 230 feet) thick, preserves old snow with unique characteristics. Solar energy transmits more heat through a polished surface than an unmodified snow surface, warming the underlying firn and driving water vapor up. Condensation follows. Decades to centuries of repeated seasonal cycles have resulted in the formation of fingernail-sized crystals, which have been misrepresented in SMB measurements due to the intensity of their recrystallization. Where other studies have wrongly interpolated field measurements across glaze regions, Scambos and his colleagues used Ground Penetrating Radar (GPR) to properly image the subsurface and determine the extent of wind-glaze regions.

Earlier climate models have assumed the scope of wind glaze on the EAIS insignificant, but with about 11 percent identified, the regions can no longer be ignored. Results show that the overall SMB has been exaggerated anywhere between 46 to 82 gigatons, a large fraction to the net imbalance, meaning the actual SMB should be slightly negative. “If accounted for properly, this means there is less snow than we thought before,” Scambos said. “The implication is that Antarctica may be contributing more to sea level rising than we currently think.”

REFERENCE

Scambos, T. A., M. Frezzoti, T. Haran, J. Bohlander, J. T. M. Lenaerts, M. R. Van Den Broeke, K. Jezek, D. Long, S. Urbini, K. Farness, T. Neumann, M. Albert, J.-G. Winther (2012), Extent of low-accumulation ‘wind glaze’ areas on the East Antarctic plateau: implications for continental ice mass balance, Journal of Glaciology, Vol. 58, No. 210, doi: 10.3189/2012JoG11J232.

Ted Scambos’s Arctic Megadunes site: http://nsidc.org/cryosphere/antarctica/megadunes

All About Snow

Laura Naranjo — Fri, 30 Nov 2012 18:07:25 +0000

Once snow crystals form in the atmosphere, they grow by absorbing surrounding water droplets. The snowflakes we end up seeing on the ground are an accumulation of these ice crystals. This magnified image of snow crystals was captured by a low-temperature scanning electron microscope (SEM). The pseudo colors commonly found in SEM images are computer generated, and in this case highlight the different flake formations. Photograph courtesy Agricultural Research Service, United States Department of Agriculture

As winter approaches the Northern Hemisphere, millions of people unpack thick coats, hats, scarves, and gloves in anticipation, and sometimes dread, of the oncoming snowy weather. Snow affects many of us in some way. People must live and work in it, and cities must find ways to remove it. Animals and plants adapt to survive in snowy regions. Snowy weather can cause dangerous conditions, or create seasonal opportunities to get out and play.

NSIDC’s recently updated educational Web site, All About Snow, can help satisfy your curiosity about snow. The site covers everything from snowflakes to snowstorms, explaining the various types of snow, both in the air and on the ground. Find out the difference between a flurry and a blizzard, how snow forms penitentes and rollers, or why snow looks white, blue, or sometimes pink or red. Learn about how people and animals cope with snow, and even use it to their advantage.

The expanded All About Snow also incorporates formerly separate educational pages from NSIDC’s cryosphere section, “Avalanche awareness” and “Have snow shovel, will travel.”

Snow and the globe

Avalanches can be caused by a variety of factors, including terrain, slope steepness, weather, temperature, and snowpack conditions. Photograph copyright Richard Armstrong, NSIDC

Many people are only interested how snow might affect the weekend’s ski reports or the morning’s commute. But snow plays a much bigger role in Earth’s climate. So scientists also try to see how snow fits into the global picture: how much snow covers the globe each winter, and how long does it last? Each year, snow covers almost 18 million square miles of Earth’s surface, with 98 percent falling during the Northern Hemisphere winter. Because it is such a large component of the cryosphere, snow influences the Earth’s energy balance, regulating heat exchange between Earth’s surface and the atmosphere.

Likewise, as climate shifts and regions warm, changes in the amount of snowfall and the extent of snow cover produce ripple effects throughout entire ecosystems. Snow that falls later in autumn and melts sooner in spring can extend growing seasons, or cause temperate plant species to creep northward into new territory. In turn, animals accustomed to snowy environments may increasingly find themselves drier and warmer for longer periods each year.

To find out more, explore the updated and expanded All About Snow site. Find out why snow matters to people, plants, and animals all over the world, or browse the list of resources about snow, blizzards, avalanches, and other related topics.

Visit All About Snow in the Education Center, or go to the Web site directly at http://nsidc.org/cryosphere/snow.

Newest eye on the cryosphere

Jane Beitler — Wed, 31 Oct 2012 23:43:49 +0000

This aerial photograph shows a melt lake forming on the Greenland ice sheet during summer. In recent years, these melt lakes have become more extensive, providing visual evidence of higher-than-average surface melt during summer that is contributing to the thinning of this massive ice sheet. Credit: J. Maurer

Once Earth’s frozen features were mostly solid and holding still, or at least moving very slowly and predictably, like the patient creep of a glacier towards its outlet. But now summer’s thaw is beginning to outpace winter’s freeze up, most strongly observed in the waning of Greenland’s ice sheet and of summer Arctic sea ice cover. Around the Antarctic Peninsula and West Antarctica, ice shelves are collapsing, the ice sheet is thinning, and glaciers are speeding up. The cryosphere is on the move.

These changes are too slow for a video camera to capture, but satellites can capture that time lapse of long-term changes seen in Earth’s coldest regions. Perhaps the longest and most consistent series of satellites is Landsat, and early next year a new Landsat will fly. This new eye in the sky promises not just to keep the record going, but to provide more detail on Earth’s forests, oceans, croplands, savannahs, snow, ice, and more.

Scientists used this Landsat image to study changes to the ice flow of Crane Glacier in Antarctica. The image was overlaid with information gathered by aircraft during NASA Operation IceBridge, which flew altimetry and other instruments over Antarctica to monitor Antarctica’s changing ice sheet and glaciers. Credit: C. A. Schuman

A bluer vision

NSIDC scientist Ted Scambos was recently named to the Landsat Science Team, which advises NASA and the USGS on Landsat operations. “Landsat has been a great mapping tool,” he said. “But it has now emerged as the best climate change detection system we’ve got as well.” The newest Landsat, planned for launch in early 2013, will be the eighth in the series. Scambos and his Landsat team colleagues in other Earth science fields will help check that data from the new instrument aligns with past data, so that researchers have an uninterrupted record of the planet. They also provide guidance to the Landsat mission that will help Landsat reach its full potential for science. Landsat has always been powerful for its high resolution, and for its range of spectral channels. It can see in the visible light spectrum, like a photograph, and it can also see in the infrared to detect thermal information, invisible to the eye but valuable for studying features of oceans and forests in greater detail. The upcoming satellite also has two extra bands, giving it higher sensitivity.

With Landsat data, scientists like Scambos were able to map ice flow on Antarctica, helping to show that glaciers were accelerating the flow of ice to the ocean after the floating ice shelves in front of them broke up. Landsat 8 will be even better for studying changes in the ice sheets, Scambos said. “The new bands, and the new precision of the sensor, are going to help in a lot of areas,” Scambos said, “especially the new blue channel. We’ll be able to map melt water lakes on the ice sheets and ice shelves in fantastic detail.” Other uses include snow and ice surface mapping, ice melt detection and melt pond measurement, and thermal mapping of debris-covered glaciers and the ocean surface near large floating glaciers.

For more information on the Landsat Program, visit their Web page at landsat.gsfc.nasa.gov.

For more information on Ted Scambos’s research, see nsidc.org/research/bios/scambos.html.

An Arctic without sea ice

Jane Beitler — Thu, 27 Sep 2012 23:50:25 +0000

Arctic animals such as these Bering Sea walruses depend on the ice edge as a platform for hunting and breeding. Photograph courtesy Brad Benter, U.S. Fish and Wildlife Service.

The rapid retreat and thinning of the Arctic sea ice cover over the past several decades is one of the most striking manifestations of global climate change. As the ice left at the end of each summer continues its sharp downward trend, setting a new record low in 2012, scientists want to understand exactly what this means for the Arctic and for Earth’s climate as a whole.

One of the grand challenges in understanding summer sea ice decline is the question of how soon the Arctic Ocean could become virtually ice-free by summer’s end. An Arctic Ocean with only discontinuous patches of ice floes is thought of as a marker of fundamental change in the Arctic climate system. More of the darker ocean surface would be exposed for a longer time, absorbing the Sun’s heat and then transmitting that heat back to the air and land. A warmer Arctic also portends warmer lower latitudes, as the Arctic weakens in its role as Earth’s air conditioner.

Modeling the decline

Computer climate models help strengthen researchers’ understanding of how Arctic sea ice loss feeds back warming into the Earth system. The models are built on current understanding of the system and past observations. Researchers can use the models to run scenarios with less sea ice cover, increased greenhouse gases in the atmosphere, and other inputs that could affect climate. When the Arctic may become ice free is but one of the important questions that they may use the models to study.

This graph comparing results from climate models shows that the actual downward trend of Arctic sea ice decline continues to exceed what most models predicted.
Courtesy Stroeve et al., Geophysical Research Letters

But tuning these climate models is a work in progress, given that scientists are modeling a moving target. One test of the models is how well they simulate current climate conditions. Previous studies revealed that the actual downward trend in September ice extent exceeded simulated trends from most models participating in the World Climate Research Programme Coupled Model Intercomparison Project Phase 3 (CMIP3). Since then, researchers have worked to refine the models.

A new study led by NSIDC scientist Julienne Stroeve shows that as a group, simulated trends from the next generation of models, CMIP5, are more consistent with observations over the satellite era (1979 to 2011). So researchers may be closer to an accurate picture of sea ice decline, yet that picture remains elusive.

Exceeding expectations

While closer, the trends from most models nevertheless remain smaller than the observed rate of decline. As of September 2012, satellite data indicated that September Arctic sea ice is currently declining at a rate of -13% per decade, compared to the 1979 to 2000 average. Modeling sea ice thickness continues to be a challenge. Thinning sea ice impacts its ability to survive the melt season, and ice thickness depends on complex factors such as rates of ice transport by winds and ocean currents, and ice melt and growth. As well, natural variability remains a factor in sea ice decline, and by its nature is hard for models to account for. This means that a prolonged series of warmer or colder years could considerably accelerate or delay ice-free summers.

Still, it is clear that if greenhouse gas concentrations continue to rise, the Arctic Ocean will eventually become seasonally ice free. While the models still do not provide a certain date, the CMIP5 models are presently suggesting that the Arctic will be seasonally ice-free Arctic sooner than 2035, what the previous model ensemble version CMIP3 suggested.

Reference

Stroeve, J. C., V. Kattsov, A. Barrett, M. Serreze, T. Pavlova, M. Holland, and W. N. Meier (2012), Trends in Arctic sea ice extent from CMIP5, CMIP3 and observations, Geophys. Res. Lett., 39, L16502, doi:10.1029/2012GL052676.

Libre frees polar data

Jane Beitler — Wed, 29 Aug 2012 16:27:59 +0000

An Arctic researcher removes a snow core sample. Credit: Andrew Slater

Knowledge is the common wealth of humanity.
–Adama Samassekou, Convener of the UN World Summit on the Information Society

Science is increasingly based on data, yet the systems and tools for sharing data lag the immediacy and variety of data being produced. The rapid changes being observed in Earth’s frozen regions—thawing ground, retreating glaciers, melting ice sheets, and waning summer sea ice extent–are a case in point. Scientists who collaborated during the recent International Polar Year identified ease of data sharing as key to help pace scientific understanding with the speed of climate-induced changes being observed. A project at NSIDC called Libre puts data sharing tools in the hands of researchers—tools that are free and easy to use, and address some of the common sticking points that prevent open sharing.

Simplifying data sharing

Libre is a project devoted to liberating science data from traditional constraints of publication, location, and findability. Leveraging open-source technology and data management standards, Libre’s Web-based tools and services make it easy for scientists to publish and advertise their data and share it with the world.

Libre provides simple tools for data sharing that can be used by individual investigators and research projects of any size.

A major challenge recognized throughout the Earth science data community is the problem of uniform discovery of all data relevant to a particular user’s needs. The problem is that in most cases, relevant data may be found in any number of discipline-specific repositories, national data centers, organizational repositories, and libraries. Or the data may not reside in any repository at all. Instead, the data may reside with an individual researcher, laboratory, or work group. In this case, it can be difficult for an investigator to find or obtain the data.

Libre allows data providers, whether an individual investigator with a single data set to share or a data repository with potentially hundreds of data sets to share, to advertise their holdings in a Web-discoverable way, and for registries to find those advertisements wherever they are located, and to aggregate those that are relevant to their particular user communities.

Tools and services

Libre offers several tools to these ends. First, the Libre Collection Caster is a Web-based tool that creates Atom feeds so data providers can advertise their data sets, and users and computers on the internet can discover the data quickly and more efficiently. The Collection Caster uses Atom technology, which means that the Collection Cast or feed can be viewed with any desktop or browser-based feed reader.

Once data are exposed to the Web, Libre’s OpenSearch Application Programming Interface (API) provides a simple way to discover and access data holdings that have been found by Libre’s web crawling and aggregation services. The API can be tailored for queries specific to a user’s research, and return ATOM feeds listing the search results.

For example, the Libre OpenSearch API underlies the NASA DAAC IceBridge Portal developed by NSIDC. From the Portal, users can subscribe to a feed listing all the related data sets that match their data query and that are known to the NSIDC system. Once subscribed, whenever a new data set matching the query criteria becomes available, or one of the existing data sets on their personal feed is updated, users are notified.

And finally, Libre makes it easy for data providers to clearly communicate to others about appropriate reuse of their data. Libre’s badging tool makes it simple to declare your data open for broad use, while asserting that such data should be used according to the Ethical Norms of Data Sharing developed by the polar science community. This tool provides the data provider with a Creative Commons badge to display on their Web pages and in their data documentation that conveys their wishes in a way readily understood by both people and data systems.

For more information, visit the Libre Web page at NSIDC.

Taking the temperature of permafrost

Laura Naranjo — Wed, 18 Jul 2012 22:48:03 +0000

Tingun Zhang and his colleagues are spending several months in west China, drilling boreholes in permafrost. The temperature data from the boreholes will help them understand whether permafrost in the region is warming, and if so, how fast. Credit: Cuicui Mu

Last summer, Tingjun Zhang spent two months in China, drilling boreholes and taking temperatures. Zhang, a senior research scientist at NSIDC, is part of a team studying permafrost in the upper reaches of the Heihe River Basin in the Qilian Mountains, which form the northeastern escarpment between the Tibetan Plateau and the Gobi Desert. Zhang’s research is part of a larger study of Heihe River basin along the north slope of the Qilian Mountains, funded by the Natural Science Foundation of China. His research team, along with nearly forty others, is hoping to gather enough data over the course of the study to form a clearer picture of how a changing climate may affect the plants, wildlife, and the people of the area.

Frozen layers

“We are looking at how changes in permafrost are affecting the region’s hydrology,” Zhang said. “We also want to understand how permafrost affects the ecosystem, because the area has grazing for sheep, cattle, and other livestock.” The permafrost underlying the study area is already considered warm, remaining only two degrees Celsius below freezing. Only a very slight warming would be disastrous for the region. “Air temperatures have increased by one degree Celsius over the past 30 years,” he said.

Tingjun Zhang and his team are researching permafrost in the Qilian Mountains of north central China. The area has been slowly warming, and thawing permafrost could change the area’s vegetation and make it more difficult for herders to find good grazing for their livestock. Credit: Tingjun Zhang

Permafrost is soil that remains frozen year-round. In many places, however, permafrost is topped by a shallow layer that scientists call an active layer, because it freezes and thaws seasonally. Over the study area that Zhang is investigating, this layer is 2 to 4 meters (6.5 to 13 feet) deep. Plants grow when an active layer is present, because the seasonal thawing releases water. The underlying permafrost acts like a barrier, locking moisture in and preventing it from draining through the soil. If this reserve of water does not remain near the surface, it could have serious consequences for grazing along the plateau. Zhang said, “As temperatures increase, the active layer gets deeper, meaning ground water levels get deeper and there is less water available near the surface to grow the vegetation animals need for grazing.”

The current temperature records rely on sparse measurements, so one of Zhang’s projects is to install instruments that will take regular temperature readings in the area and develop a long-term record. He will return to China over the next few summers to continue his research and learn how permafrost in the region is responding to this gradual warming. He and his team will map the distribution of permafrost as well as the development of the active layer that irrigates the grasslands.

Considering carbon

Changes in permafrost could have more wide ranging affects, as well, because thawing permafrost releases carbon into the atmosphere. “There is a lot of carbon stored in permafrost, and it could really contribute to global warming,” Zhang said. He and his team will start investigating how much carbon might be released, should the area continue to warm. Carbon is a potent greenhouse gas, so thawing permafrost could fuel a global feedback loop that further warms the atmosphere.