Areas near the equator are frequently cloudy, obscuring the view of Earth’s surface from space. April 7, 2017, was no different. On that day, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this natural-color image of clouds over the Gilbert Islands. The remote island chain is part of the Republic of Kiribati, and straddles the equator in the central Pacific Ocean.

These clouds, however, were not your typical tropical rainstorm. Instead, the parallel “roll clouds” were likely influenced by the development of Tropical Cyclone Cook to the south. At the time, Cook was strengthening near Vanuatu and heading toward New Caledonia.

“As far as tropical cyclones go, we believe that they are a nearly ideal environment for roll formation,” said Ralph Foster, an atmospheric scientist at the University of Washington. The extreme wind shear associated with cyclones generates additional turbulence in the already turbulent layer of air near Earth’s surface. According to Foster, the turbulent flow in this layer “self-organizes,” forming long rolls of counter-rotating air.

More precisely, the atmosphere has alternating clockwise and counter-clockwise circulation. In between the overturning circulations are updrafts and downdrafts. If conditions are right for clouds to form, clouds will grow in the updraft zone and be suppressed in the downdraft. The resulting linear cloud features can persist for hours.

But just because these convective rolls are happening in the atmosphere does not necessarily mean there will be clouds. “The clouds themselves contribute little to the roll dynamics,” Foster said. “We think of these clouds as convenient flow visualizations.”

The hazy, vertical strip obscuring part of the image is sunlight mirrored from the ocean surface, known as “sunglint.”

Annotated image and further reading: NASA’s Earth Observatory
Tour Earth’s Clouds From Space

Image Credit: NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response
Caption: Kathryn Hansen

 

New Zealand contains over 3,000 glaciers, most of which are in the Southern Alps on the South Island. Since 1890, the glaciers have been retreating, with short periods of small advances. The differences between 1990 (Landsat image from January 12) and 2017 (ASTER image  from January 29) can be seen in the pair of images, that include the Mueller, Hooker and Tasman Glaciers. Notice the larger terminal lakes, the retreat of the ice free of moraine cover, and the higher moraine walls due to ice thinning. The images cover an area of 39 by 46 km, and are located at 43.7 degrees south, 170 degrees east.

With its 14 spectral bands from the visible to the thermal infrared wavelength region and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched Dec. 18, 1999, on Terra. The instrument was built by Japan’s Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and data products.

The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

The U.S. science team is located at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA’s Science Mission Directorate, Washington, D.C.

More information about ASTER is available at http://asterweb.jpl.nasa.gov/.

Image credit: NASA/METI/AIST/Japan Space Systems, and U.S./Japan ASTER Science Team

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The Larsen Ice Shelf is situated along the northeastern coast of the Antarctic Peninsula, one of the fastest-warming places on the planet. In the past three decades, two large sections of the ice shelf (Larsen A and B) have collapsed. A third section (Larsen C) seems like it may be on a similar trajectory, with a new iceberg poised to break away soon.

The mosaic above, centered on the northern part of Larsen Ice Shelf, is comprised of four natural-color satellite images captured by the Operational Land Imager (OLI) on Landsat 8 on Jan. 6 and 8, 2016. It shows the remnant of Larsen B, along with the Larsen A and smaller embayments to the north covered by a much thinner layer of sea ice. The remaining shelf appears white with some deep rifts within it.

Areas with sea ice anchored to the coastline or ice shelf—fast ice—are light blue where covered with melt water and white where covered by wind-blown snow. The ocean is dark, nearly black, where it is not covered by sea ice. The white areas near where glaciers meet the sea have multitudes of small icebergs called bergy bits that broke off from land ice.

Extended caption and annotated images: NASA’s Earth Observatory

Image Credit: NASA Earth Observatory image by Jesse Allen, using Landsat data from the U.S. Geological Survey
Caption: Adam Voiland

 

Yamzho Yumco (Sacred Swan) Lake in Tibet is surrounded by snow-capped mountains and is one of the three largest sacred lakes. It is highly crenellated with many bays and inlets. The lake is home to Samding Monastery, headed by a female re-incarnation (Wikipedia). The image was acquired March 6, 2014, covers an area of 49.8 by 60 km, and is centered at 28.9 degrees north, 90.6 degrees east.

With its 14 spectral bands from the visible to the thermal infrared wavelength region and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched Dec. 18, 1999, on Terra. The instrument was built by Japan’s Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and data products.

The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

The U.S. science team is located at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA’s Science Mission Directorate, Washington, D.C.

More information about ASTER is available at http://asterweb.jpl.nasa.gov/.

Image credit: NASA/METI/AIST/Japan Space Systems, and U.S./Japan ASTER Science Team

 

 

From the Arctic to the Mojave Desert, terrestrial and marine habitats are rapidly changing. These changes impact animals that are adapted to specific ecological niches, sometimes displacing them or reducing their numbers. From their privileged vantage point, satellites are particularly well-suited to observe habitat transformation and help scientists forecast impacts on the distribution, abundance and migration of animals.

 

In a press conference Monday at the American Geophysical Union meeting in San Francisco, three researchers discussed how detailed satellite observations have facilitated ecological studies of change over time. The presenters discussed how changes in Arctic sea ice cover have helped scientists predict a 30 percent drop in the global population of polar bears over the next 35 years. They also talked about how satellite imagery of dwindling plant productivity due to droughts in North America gives hints of how both migratory herbivores and their predators will fare. Finally, they also discussed how satellite data on plant growth indicate that the concentration of wild reindeer herds in the far north of Russia has not led to overgrazing of their environment, as previously thought.

 

Long-term polar bear declines

 

Polar bears depend on sea ice for nearly all aspects of their life, including hunting, traveling and breeding. Satellites from NASA and other agencies have been tracking sea ice changes since 1979, and the data show that Arctic sea ice has been shrinking at an average rate of about 20,500 square miles (53,100 square kilometers) per year over the 1979-2015 period. Currently, the status of polar bear subpopulations is variable; in some areas of the Arctic, polar bear numbers are likely declining, but in others, they appear to be stable or possibly growing.

 

“When we look forward several decades, climate models predict such profound loss of Arctic sea ice that there’s little doubt this will negatively affect polar bears throughout much of their range, because of their critical dependence on sea ice,” said Kristin Laidre, a researcher at the University of Washington’s Polar Science Center in Seattle and co-author of a study on projections of the global polar bear population. Eric Regehr of the U.S. Fish and Wildlife Service in Anchorage, Alaska, led the study, which was published on December 7 in the journal Biology Letters.

 

“On short time scales, we can have variable responses to the loss of sea ice among subpopulations of polar bears,” Laidre said. “For example, in some parts of the Arctic, such as the Chukchi Sea, polar bears appear healthy, fat and reproducing well — this may be because this area is very ecologically productive, so you can lose some ice before seeing negative effects on bears. In other parts of the Arctic, like western Hudson Bay, studies have shown that survival and reproduction have declined as the availability of sea ice declines.”

 

Regehr, Laidre and their colleagues’ results are the product of the International Union for Conservation of Nature’s (IUCN) Red List assessment for polar bears. To determine the level of threat to a species, IUCN requests scientists to project what the species population numbers will be after three generations. Using data collected from adult females in 11 subpopulations of polar bears across the Arctic, Regehr and Laidre’s team calculated the generation length for polar bears—the average age of reproducing adult females—to be 11.5 years. They then used the satellite record of Arctic sea ice extent to calculate the rates of sea ice loss and then projected those rates into the future, to estimate how much more the sea ice cover may shrink in approximately three polar bear generations, or 35 years.

 

Lastly, the scientists evaluated different scenarios for the relationships between polar bear abundance and sea ice. In one of them, the bear numbers declined directly proportionally with sea ice. In the other scenarios, the researchers used the existing, albeit scarce, data on how polar bear abundance has changed with respect to sea ice loss, using all available data from polar bear subpopulations in the four existing polar bear eco-regions, and projected forward these observed trends. They concluded that, based on a median value across all scenarios, there’s a high probability of a 30 percent decline in the global population of polar bears over the next three to four decades, which supports listing the species as vulnerable on the IUCN Red List.

 

“It is difficult to predict what population numbers will be in the future, especially for animals that live in vast and remote regions,” Regehr said. “But at the end of the day, polar bears need sea ice to be polar bears. This study adds to a growing body of evidence that the species will likely face large declines as loss of their habitat continues.”

 

Drought and mountain lions

 

The southwestern United States is expected to become more prone to droughts with climate change. The resulting loss of vegetation will not only impact herbivores like mule deer; their main predator, mountain lions, might take an even larger hit.

 

To estimate the numbers and distribution of mule deer and mountain lions in Utah, Nevada and Arizona, David Stoner, a wildlife ecologist at Utah State University in Logan, Utah, used imagery of plant productivity from the Moderate Resolution Imaging Spectroradiometer, flown on NASA’s Terra and Aqua satellites, plus radio-telemetry measurements of animal density and movements. He found that there is a very strong relationship between plant productivity and deer and mountain lion density.

 

“Measuring abundance of mule deer in the western United States is logistically difficult, hazardous and very expensive. For mountain lions, it’s even worse,” Stoner said. “But measuring changes in vegetation is relatively easy and more affordable. With this research, we’ve provided a model that wildlife managers can use to estimate the density of deer and mountain lions, two big game species of great economic importance.”

 

Using maps of vegetation productivity during a severe drought that occurred in the southwestern United States in 2002, Stoner modeled what would be the deer and mountain lion distribution and abundance, should extreme drought become the norm.

 

“During 2002, there was a 30 percent decrease from the historical record mean in precipitation,” Stoner said. “Using measurements of vegetation stressed by drought, our model predicted a 22 percent decrease in deer density. For mountain lions, the decline was 43 percent. Mountain lions occur at far lower densities than deer, and so any loss of their prey can have disporportionate impacts on their reproductive rates and overall abundance.”

 

Mule deer are popular game animals, bringing in hundreds of millions of dollars to rural areas through recreational hunting and tourism. But deer can also have adverse economic impacts; they cause vehicle collisions, devour crops and damage gardens.

 

“Droughts will make human landscapes more attractive to deer, because farms and suburban areas are irrigated and would remain fairly green,” Stoner said. “And mountain lions will go wherever the deer are. We’re going to lose some of the economic benefits of having those animals, because they’ll be fewer of them, but the costs are going to increase because the remaining animals will be attracted to cities and farms.”

 

Longer journeys for wild reindeer

 

The Taimyr reindeer herd in the northernmost region of Russia is the largest wild reindeer herd in the world and a key of source of food for the indigenous population of the Taimyr Peninsula.

 

“Reindeer populations are declining all over the world, in some places catastrophically; in Taimyr, there has been an about 40 percent drop since 2000 and the herd is now at 600,000 animals,” said Andrey Petrov, an associate professor at the University of Northern Iowa, in Cedar Falls.

 

Petrov examined historical data going back to 1969 and determined that there are ongoing changes in the distribution and migration patterns of the wild reindeer due to climate change and human pressure. The reindeer have moved east, away from human activity. At the same time, the herd is now traveling farther north and higher in elevation during the summer, possibly to avoid increasing temperatures and more abundant mosquitoes.

 

“Taimyr reindeer now have to travel longer distances between their winter and summer grounds, and this is causing a higher calf mortality,” Petrov said. “Other factors contributing to the higher mortality are the increased mosquito harassment and the fact that rivers are opening earlier than before and the animals have to cross them during their migration.”

 

Petrov also used imagery from the NASA/United States Geological Survey Landsat satellite program to determine how the presence of reindeer in their summer grounds impacts vegetation. He found that, as expected, plant biomass decreased while the reindeer were grazing, but it bounced back a few weeks after the animals left the area. This finding argues against overgrazing as a possible factor for the Taimyr reindeer population decline that occurred after 2000.

 

“The work discussed at today’s press conference is emblematic of the many ways in which satellite remote sensing supports our efforts at natural resource management and wildlife conservation,” said Woody Turner, program scientist for NASA’s Biological Diversity Program at NASA Headquarters in Washington.

 

Laidre and Stoner’s research projects received funding from NASA. The National Science Foundation funded Petrov’s research.

Related Links

 

• NASA’s AGU website
• NASA’s Aqua website
• NASA’s Terra website
• NASA’s Landsat website
• USGS Landsat website

 

 

As scientists and crew with NASA’s Operation IceBridge mission prepared for a research flight on Nov. 5, 2016, the weather in Punta Arenas, Chile, was cold, wet, and windy. But when they reached their survey site in West Antarctica, skies were clear and winds were calm—a perfect day for scientists to collect data over the Getz Ice Shelf.

IceBridge, now in its eighth year, continues to build a record of how ice is responding to changes in the polar environment. The Getz Ice Shelf in West Antarctica is one area that scientists try to examine each year. “Getz is an ice shelf that has been experiencing some of the highest basal melt rates of the Antarctic ice shelves,” said Nathan Kurtz, IceBridge project scientist and a sea ice researcher at NASA’s Goddard Space Flight Center.

The image above shows a views of Getz as photographed on Nov. 5 from a NASA research airplane by Jeremy Harbeck, a sea ice scientist at NASA Goddard. The image shows ice in the process of calving from the front of the shelf, soon to become an iceberg. 

Kurtz notes that the team has flown over the Getz Ice Shelf many times before. Flight paths are often exact repeats of those flown in previous years, which helps scientists understand how the height of the ice surface changes over time. This year, new flights over Getz were added to the existing observations. Scientists mapped the bathymetry (shape and depth of the seafloor) below the ice shelf, and they mapped the ice surface and bedrock upstream of the grounding line.

The flight over Getz is just one of a number of key areas flown during the IceBridge campaign. Each flight plan is prioritized in order of importance: baseline (the highest priority), high, medium, and low. The flight on Nov. 5 over Getz, for example, was categorized as “high” priority. Since the start of 2016 science flights on Oct.14, the team has flown six out of eight baseline missions, eight out of 15 high priority lines, and one medium and low priority mission each. Research flights for the season continue through Nov. 18.

“We are in pretty good shape so far, having flown so many missions due to a combination of favorable weather, no major airplane issues, and all instruments operating well,” Kurtz said. “We’re about four weeks into the campaign, and it’s possible we could tie the record of most flights flown with Operation IceBridge if things continue to go well.”

Additional images and related reading: NASA’s Earth Observatory

Image Credit: NASA/Jeremy Harbeck
Caption: Kathryn Hansen

 

NASA researchers have helped produce the first map showing what parts of the bottom of the massive Greenland Ice Sheet are thawed – key information in better predicting how the ice sheet will react to a warming climate.

 

Greenland’s thick ice sheet insulates the bedrock below from the cold temperatures at the surface, so the bottom of the ice is often tens of degrees warmer than at the top, because the ice bottom is slowly warmed by heat coming from the Earth’s depths. Knowing whether Greenland’s ice lies on wet, slippery ground or is anchored to dry, frozen bedrock is essential for predicting how this ice will flow in the future, But scientists have very few direct observations of the thermal conditions beneath the ice sheet, obtained through fewer than two dozen boreholes that have reached the bottom. Now, a new study synthesizes several methods to infer the Greenland Ice Sheet’s basal thermal state –whether the bottom of the ice is melted or not– leading to the first map that identifies frozen and thawed areas across the whole ice sheet.

 

“We’re ultimately interested in understanding how the ice sheet flows and how it will behave in the future,” said Joe MacGregor, lead author of the study and a glaciologist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “If the ice at its bottom is at the melting point temperature, or thawed, then there could be enough liquid water there for the ice to flow faster and affect how quickly it responds to climate change.”

 

For this study, published last month in the Journal of Geophysical Research – Earth Surface, MacGregor’s team combined four different approaches to investigate the basal thermal state. First, they examined results from eight recent computer models of the ice sheet, which predict bottom temperatures.  Second, they studied the layers that compose the ice sheet itself, which are detected by radars onboard NASA’s Operation IceBridge aircraft and suggest where the bottom of the ice is melting rapidly. Third, they looked at where the ice surface speed measured by satellites exceeds its “speed limit”, the maximum velocity at which the ice could flow and still be frozen to the rock beneath it. Fourth, they studied imagery from the Moderate Resolution Imaging Spectroradiometers on the NASA Terra and Aqua satellites looking for rugged surface terrain that is usually indicative of ice sliding over a thawed bed.

 

“Each of these methods has strengths and weaknesses. Considering just one isn’t enough. By combining them, we produced the first large-scale assessment of Greenland’s basal thermal state,” MacGregor said.

 

For each method, MacGregor’s team looked for areas where the technique confidently inferred that the bed of Greenland’s ice sheet was thawed or frozen. They then looked at the places where these methods agreed and classified these areas as likely thawed or likely frozen. The zones where there was insufficient data or the methods disagreed, they classified as uncertain.

 

From this synthesis, MacGregor and his colleagues determined that the bed is likely thawed under Greenland’s southwestern and northeastern ice drainages, while it’s frozen in the interior and west of the ice sheet’s central ice divide. For a third of the Greenland ice sheet, there’s not enough data available to determine its basal thermal state.

 

MacGregor said the team’s map is just one step in fully assessing the thermal state of the bottom of Greenland’s ice sheet.

 

“I call this the piñata, because it’s a first assessment that is bound to get beat up by other groups as techniques improve or new data are introduced. But that still makes our effort essential, because prior to our study, we had little to pick on,” MacGregor said.

 

 

 

 

 

On April 5, 2015, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired this natural-color image of sea ice off the coast of East Antarctica’s Princess Astrid Coast.

White areas close to the continent are sea ice, while white areas in the northeast corner of the image are clouds. One way to better distinguish ice from clouds is with false-color imagery. In the false-color view of the scene here, ice is blue and clouds are white.

The image was acquired after Antarctic sea ice had passed its annual minimum extent (reached on Feb. 20, 2015), and had resumed expansion toward its maximum extent (usually reached in September).

More information: NASA’s Earth Observatory

Image Credit: NASA/Jeff Schmaltz, LANCE/EOSDIS Rapid Response
Caption: Kathryn Hansen

 

This image from the MODIS instrument aboard NASA’s Terra satellite shows the U.S. Northeast and the surrounding area on Jan. 28, 2015, following intense winter weather in New England earlier in the week.

› Labeled version (101 MB png)

Image Credit: NASA

 

A small hole in the clouds revealed newly formed sea ice in the Bellingshausen Sea next to an ice berg on Nov. 5, 2014 flight.

Photo: NASA/Digital Mapping System

The voyage of Iceberg B-31 continued in January, 2014 as the giant iceberg drifted over the frigid waters of Pine Island Bay and widened the gap between the newly-calved iceberg and the “mother” glacier.

Between November 9 and 11, 2013 a giant crack in the Pine Island Glacier gave completely away, liberating Iceberg B-31 from the end of the glacial tongue. The new iceberg was estimated to be 35 km by 20 km (21 mi by 12 mi) in size – or roughly the size of Singapore.

On January 5, 2014 the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite captured this true-color image of B-31 floating in the center of Pine Island Bay on an approach to the Amundsen Sea. Pine Island Glacier can be seen on the upper right coast of the bay, and is marked by parallel lines in the ice. According to measurements reported by the National U.S. Ice Center, on January 10, B-31 was maintaining its size, and was located at 74°24’S and 104°33’W.

Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team

 

On most days, relentless rivers of clouds wash over Alaska, obscuring most of the state’s 6,640 miles (10,690 kilometers) of coastline and 586,000 square miles (1,518,000 square kilometers) of land. The south coast of Alaska even has the dubious distinction of being the cloudiest region of the United States, with some locations averaging more than 340 cloudy days per year.

That was certainly not the case on June 17, 2013, the date that the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired this rare, nearly cloud-free view of the state. The absence of clouds exposed a striking tapestry of water, ice, land, forests, and even wildfires.

Snow-covered mountains such as the Alaska Range and Chugach Mountains were visible in southern Alaska, while the arc of mountains that make up the Brooks Range dominated the northern part of the state. The Yukon River – the longest in Alaska and the third longest in the United States – wound its way through the green boreal forests that inhabit the interior of the state. Plumes of sediment and glacial dust poured into the Gulf of Alaska from the Copper River. And Iliamna Lake, the largest in Alaska, was ice free.

The same ridge of high pressure that cleared Alaska’s skies also brought stifling temperatures to many areas accustomed to chilly June days. Talkeetna, a town about 100 miles north of Anchorage, saw temperatures reach 96°F (36°C) on June 17. Other towns in southern Alaska set all-time record highs, including Cordova, Valez, and Seward. The high temperatures also helped fuel wildfires and hastened the breakup of sea ice in the Chukchi Sea.

Image Credit: NASA/Jeff Schmaltz, LANCE MODIS Rapid Response Team, NASA GSFC
Caption: Adam Voiland

 

NASA’s Terra satellite passed over the South Atlantic Ocean on Nov. 15, 2012, allowing the Moderate Resolution Imaging Spectroradiometer instrument flying aboard to capture this true-color image of St. Helena Island and the band of wind-blown cloud vortices trailing towards the island’s leeward side.

St. Helena Island is a tiny island lying approximately 1,860 kilometers (1,156 miles) west of Africa. Volcanic in origin, it has rugged topography with steep, sharp peaks and deep ravines. Wind, which can blow unimpeded for hundreds of miles across the ocean, strikes the face of the mountains, and is forced around the unyielding terrain. As it blows around the island, the air spins on the leeward side, much like a flowing river forms eddies on the downriver side of a piling. The spinning wind forms intricate – and mathematically predictable – patterns. When clouds are in the sky, these beautiful patterns become visible from above.

Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team

 

In mid-October 2011, NASA scientists working in Antarctica discovered a massive crack across the Pine Island Glacier, a major ice stream that drains the West Antarctic Ice Sheet. Extending for 19 miles (30 kilometers), the crack was 260 feet (80 meters) wide and 195 feet (60 meters) deep. Eventually, the crack will extend all the way across the glacier, and calve a giant iceberg that will cover about 350 square miles (900 square kilometers). This image from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NAS’s Terra spacecraft was acquired Nov. 13, 2011, and covers an area of 27 by 32 miles (44 by 52 kilometers), and is located near 74.9 degrees south latitude, 101.1 degrees west longitude.

Image Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team

 

Like rivers of liquid water, glaciers flow downhill, with tributaries joining to form larger rivers. But where water rushes, ice crawls. As a result, glaciers gather dust and dirt, and bear long-lasting evidence of past movements.

Alaska’s Susitna Glacier revealed some of its long, grinding journey when the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite passed overhead on Aug. 27, 2009. This satellite image combines infrared, red and green wavelengths to form a false-color image. Vegetation is red and the glacier’s surface is marbled with dirt-free blue ice and dirt-coated brown ice. Infusions of relatively clean ice push in from tributaries in the north. The glacier surface appears especially complex near the center of the image, where a tributary has pushed the ice in the main glacier slightly southward.

Susitna flows over a seismically active area. In fact, a 7.9-magnitude quake struck the region in November 2002, along a previously unknown fault. Geologists surmised that earthquakes had created the steep cliffs and slopes in the glacier surface, but in fact most of the jumble is the result of surges in tributary glaciers.

Glacier surges-typically short-lived events where a glacier moves many times its normal rate-can occur when melt water accumulates at the base and lubricates the flow. This water may be supplied by meltwater lakes that accumulate on top of the glacier; some are visible in the lower left corner of this image. The underlying bedrock can also contribute to glacier surges, with soft, easily deformed rock leading to more frequent surges.

Image Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science

 

The Wilkins Ice Shelf, on the western side of the Antarctic Peninsula, experienced multiple disintegration events in 2008. By the beginning of 2009, a narrow ice bridge was all that remained to connect the ice shelf to ice fragments fringing nearby Charcot Island. That bridge gave way in early April 2009. Days after the ice bridge rupture, on April 12, 2009, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite took this image of the southern base of the ice bridge, where it connected with the remnant ice shelf. Although the ice bridge has played a role in stabilizing the ice fragments in the region, its rupture doesn’t guarantee the ice will immediately move away.

With its 14 spectral bands from the visible to the thermal infrared wavelength region and its high spatial resolution of about 50 to 300 feet, ASTER images Earth to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched Dec. 18, 1999, on NASA’s Terra satellite. The instrument was built by Japan’s Ministry of Economy, Trade and Industry. A joint U.S./Japan science team maintains the instrument and its data products.

Image Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team
 

 

On the northwestern coast of Madagascar, the salty waters of the Mozambique Channel penetrate inland to join with the freshwater outflow of the Betsiboka River, forming Bombetoka Bay. Numerous islands and sandbars have formed in the estuary from the large amount of sediment carried in by the Betsiboka River and have been shaped by the flow of the river and the push and pull of tides.

This image from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite shows Bombetoka Bay just upstream of where it opens up into the Mozambique Channel, which separates Madagascar from Africa to the west. In the image, water is sapphire and tinged with pink where sediment is particularly thick. Dense vegetation is deep green.

Image Credit: NASA

 

The massive C-19 iceberg, which broke from the Ross Ice Shelf in Antarctica in May 2002, is the long smooth section of ice just right of the center of the image. The iceberg is trapped by sea ice along the George V coast, the section of Antarctica near Australia, in this Moderate Resolution Imaging Spectroradiometer (MODIS) image taken by the Terra satellite on March 1, 2004. When it formed, C-19 was larger than the state of Delaware at 32 km (almost 20 miles) wide and 200 km (124 miles) long, but not as large as the B-15 iceberg that broke off of the same ice shelf in 2001; nevertheless, C-19 is among the largest icebergs ever recorded.

Image Credit: Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC