Image of China’s Poyang lake from the synthetic aperture radar (SAR) on the Sentinel-1A satellite, acquired on 12 May 2014 in dual polarization. The radar gathers information in either horizontal or vertical polarizations, shown here as a composite (HH in red, HV in green and HH-HV in blue).
Poyang is just one of the many project areas of the collaborative Chinese-European Dragon Program, which marked its ten-year anniversary this week. Read more.
Amanda, the first named storm of the 2014 hurricane season in the Americas, is seen off the west coast of Mexico in an image acquired on May 25 by the Moderate Resolution Imaging Spectrometer (MODIS) on NASA's Aqua satellite. At the time of the image, Amanda was a category 4 hurricane. Amanda's winds peaked at 155 miles (250 kilometers) per hour, making it the strongest May hurricane on record in the eastern Pacific. In the image, Hurricane Amanda sports a distinct eye as well as heavy rain bands wound tightly around the center.
This false-color image of Peru's Ubinas volcano was acquired on April 14, 2014, by NASA's Uninhabited Aerial Vehicle Synthetic Aperture Radar, or UAVSAR. Located about 100 miles (160 kilometers) from the city of Arequipa, Ubinas is Peru's most active volcano.
UAVSAR flew exactly the same flight path over Ubinas in 2013. By combining the images from the two years, researchers will produce detailed maps of surface motions that can improve models of volcanic deformation.
The Kerguelen Islands (also known as the Desolation Islands) are part of the French Southern and Antarctic lands. Located in the southern Indian Ocean, the islands are among the most isolated places on Earth, more than 3200 km away from the nearest populated location. The largest island is Grand Terre (120 by 150 km), with the capital city of Port-aux-Francais. Total population is around 100; all travel and transport is by ship. The French Space Agency operates a satellite and tracking station near the town. The image shows the eastern part of the island, and covers an area of 43 by 35 km, is located at 49.3 degrees south, 69.4 degrees east, and was acquired February 27, 2009.
Winter still grips the volcanoes on Russia's Kamchatka peninsula. In this new image, acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra spacecraft, the mantle of white is disturbed by dark ash entirely covering Sheveluch volcano from recent eruptions. During the previous week, ash plumes rising up to 6.2 miles (10 kilometers) were reported by the Kamchatka Volcanic Eruption Response Team. The image was acquired May 15, 2014, and is located at 56.6 degrees north, 160.6 degrees east.
Three years of measurements from CryoSat show that the Antarctic Ice Sheet is now losing 159 billion tonnes of ice each year, enough to raise global sea levels by 0.45 mm per year. Read full article.
Although the Amundsen Sea region is only a fraction of the whole West Antarctic Ice Sheet, the region contains enough ice to raise global sea levels by 4 feet (1.2 meters).
The new finding that the eventual loss of a major section of West Antarctica's ice sheet "appears unstoppable" was not completely unexpected by scientists who study this area. The study, led by glaciologist Eric Rignot at NASA's Jet Propulsion Laboratory, Pasadena, California, and the University of California, Irvine, follows decades of research and theory suggesting the West Antarctic Ice Sheet is inherently vulnerable to change.
Antarctica is so harsh and remote that scientists only began true investigation of its ice sheet in the 1950s. It didn't take long for the verdict on the West Antarctic Ice Sheet to come in. "Unstable," wrote Ohio State University glaciologist John Mercer in 1968. It was identified then and remains today the single largest threat of rapid sea level rise.
Why is West Antarctica's ice sheet considered "unstable"?
The defining characteristic of West Antarctica is that the majority of the ice sheet is "grounded" on a bed that lies below sea level.
In his 1968 paper, Mercer called the West Antarctic Ice Sheet a "uniquely vulnerable and unstable body of ice." Mercer based his statement on geologic evidence that West Antarctica's ice had changed considerably many, many millennia ago at times when the ice sheets of East Antarctica and Greenland had not.
In 1973, University of Maine researcher Terry Hughes asked the question that scientists continue to investigate today. The title of his paper: "Is The West Antarctic Ice Sheet Disintegrating?" In 1981, Hughes published a closer look at the Amundsen Sea region specifically. He called it "the weak underbelly of the West Antarctic ice sheet."
Here's the cause for concern: When the ice sheet is attached to a bed below sea level, ocean currents can deliver warm water to glacier grounding lines, the location where the ice attaches to the bed.
Scientists recognized that this is the first step in a potential chain reaction. Ocean heat eats away at the ice, the grounding line retreats inland and ice shelves lose mass. When ice shelves lose mass, they lose the ability to hold back inland glaciers from their march to the sea, meaning those glaciers can accelerate and thin as a result of the acceleration. This thinning is only conducive to more grounding line retreat, more acceleration and more thinning. In this equation, more ice flows to sea every year and sea level rises.
But that's not all.
Beginning with research flights in the 1960s that made radar measurements over West Antarctica, scientists began to understand that, inland of the ice sheet's edge, the bed slopes downward, precipitously, in some cases.
This downward, inland slope was theorized decades ago, but has been confirmed and mapped in detail in recent years by airborne campaigns such as NASA's Operation IceBridge. In some spots the bed lies more than a mile and a half below sea level. The shape of this slope means that when grounding lines start to retreat, ocean water can infiltrate between the ice and the bed and cause the ice sheet to float off its grounding line.
Why is the Amundsen Sea region more at risk than other parts of West Antarctica?
In addition to the ice sheet being grounded below sea level, there are three main reasons. First, the glaciers here lack very large ice shelves to stem ice flow. Second, they aren't "pinned" by obstructions in their beds except in a few small places, unlike the Ronne and Ross shelves which are pinned down by large islands. Third, as first observed in the 1990s, the area is vulnerable to a regional ocean current, ushered in by the shape of the sea floor and the proximity of the circumpolar deep current. This current delivers warm water to grounding lines and the undersides of ice shelves in the region.
The pace and magnitude of the changes observed in this region match the expectation that Amundsen Sea embayment glaciers should be less stable than others. In some cases, the changes have outstripped expectations.
Pine Island and Thwaites glaciers have experienced significant flow acceleration since the 1970s. Both saw the center of their grounding lines retreat dramatically. From 1992 to 2011, Pine Island's grounding line retreated by 19 miles (31 kilometers) while the center of the Thwaites grounding line retreated by nearly 9 miles (14 kilometers). Annual ice discharge from this region as a whole has increased 77 percent since 1973.
What would a loss of the Amundsen Sea region mean for sea level rise?
Even as Rignot and colleagues suggest that loss of the Amundsen Sea embayment glaciers appears inevitable, it remains extremely difficult to predict exactly how this ice loss will unfold and how long it will take. A conservative estimate is that it could take several centuries.
The region contains enough ice to raise global sea levels by 4 feet (1.2 meters). The most recent U.N. Intergovernmental Panel on Climate Change (IPCC) report estimates that by 2100, sea level will rise somewhere from just less than 1 foot to about 3 feet (26 to 98 centimeters). But the vast majority of these projections do not take into account the possibility of major ice loss in Antarctica. Rignot said this new study suggests sea level rise projections for this century should lean toward the high-end of the IPCC range.
The Amundsen Sea region is only a fraction of the whole West Antarctic Ice Sheet, which if melted completely would raise global sea level by about 16 feet (5 meters).
What are NASA and other science agencies doing to better understand this vulnerable region and its potential impact on global sea level?
To better understand how this section of the ice sheet has changed in recent decades, scientists from NASA and research institutions around the world have made field campaigns to the region and used every airborne and spaceborne tool at their disposal, including NASA satellites and those launched by space agencies in Europe, Japan and Canada.
The National Science Foundation has funded major field campaigns to West Antarctica, including POLENET, which place Global Positioning System (GPS) stations in the area to measure geological changes. A campaign to the Pine Island Glacier ice shelf led by NASA glaciologist Bob Bindschadler measured variables such as water temperature and melting rate at the underside of the ice shelf.
NASA's Operation IceBridge, which began in 2009, continues to fly one extended research campaign over Antarctica each year. IceBridge flights put multiple scientific instruments over key regions of the ice sheet to measure glacier thinning, the shape of the bed and other factors.
In 2017, NASA will launch ICESat-2, the follow-up mission to ICESat, which operated from 2003 to 2009. ICESat-2 will use laser altimetry to make precise measurements of glacier heights. Combined with the ICESat and IceBridge data records, the ICESat-2 measurements will allow for a continuous record of year-over-year change in some of the most remote regions of the world.
Along the Bangladeshi coast north of Chittagong, ships from around the world are beached and dismantled. Many kilometers of mangrove have been cleared for the more than 80 shipbreaking yards. The image was acquired March 12, 2013, covers an area of 10.5 by 12 km, and is located at 22.4 degrees north, 91.7 degrees east.
The Nagarunja Sagar Dam on India's Krishna River was built between 1955 and 1972. Erected by the hand labor of 125,000 workers, it is the largest masonry dam in operation in the world. Standing at 120m high, and 800m long, it is made up of huge rocks and mortar. The image was acquired April 11, 2012, covers an area of 16 by 16 km, and is located at 16.6 degrees north, 79.3 degrees east.
The snow-capped mountains running through the center of this satellite image are part of the Cordillera Blanca – or ‘white range’ – in South America’s Andes. Even though they are part of the typically warm Tropics – the region of Earth surrounding the equator – the mountain range is high enough to be permanently covered in snow and ice.
There are hundreds of glaciers in this range, providing a major source of water for irrigation and hydroelectric power. The glaciers and snow-covered areas ‘collect’ rain and snow during the rainy season and slowly release it during the drier times of the year. Over the last decades, the glaciers have experienced major losses owing to climate change, causing a major threat to water supply during the dry season in the future.
Located near the center of this image, Mount Huascarán is the highest peak in Peru at 6768 m. The summit is one of the farthest points from Earth’s center, meaning it experiences the lowest gravity on the planet.
North of Huascarán, we can see an outlet glacier that meets another outlet from the Chopicalqui mountain to the east. Numerous blue glacial lakes are visible in the valleys between the mountains.
The Huascarán National Park protects this mountainous area, and has been on the UNESCO world heritage list since 1985. The spectacled bear, puma, mountain cat, white-tailed deer and vicuna are important indigenous species, but have all been heavily hunted in the past.
This image, acquired by Japan’s ALOS satellite on 24 August 2010, is featured on the Earth from Space video program.
The Nile Delta in Egypt, acquired by Proba-V on 24 March 2014.
Celebrating one year since the miniature Proba-V satellite was launched from French Guiana in the early hours of 7 May 2013.
The 'V' stands for 'vegetation': the satellite was designed to provide a clear picture of the world’s plants so their health can be easily monitored. This information can also be used for day-by-day tracking of extreme weather, alerting authorities to crop failures, monitoring inland water resources and tracing the steady spread of deserts and deforestation.
See our gallery for more images from Proba-V's first year of operation: http://www.esa.int/Our_Activities/Observing_the_Earth/Proba-V/Highlights/Happy_Birthday_Proba-V
Sentinel-1A radar acquisition from 22 April 2014 showing Greece’s Attica region, with mountainous areas and the capital and largest city of Athens near the center. In the water, different shades of blue indicate different types of sea surface, influenced by currents and waves. The image was acquired in ‘interferometric wide swath’ mode and with a dual polarization in VV and VH. Colors were assigned to different types of radar polarizations.
False color Proba-V image from 4 February 2014 showing deforestation in Brazil.
This radar image is one of the first from the Sentinel-1A satellite, acquired on 20 April – less than three weeks after its launch on 3 April.
The image shows the Salar de Uyuni in Bolivia, which is the largest salt flat in the world.
Occupying over 10,000 sq km, the vast Salar de Uyuni lies at the southern end of the Altiplano, a high plain of inland drainage in the central Andes. Some 40,000 years ago, this area was part of a giant prehistoric lake that dried out, leaving behind the salt flat.
While the salt flat appears an almost homogenous white in optical satellite imagery, here we see it in shades of grey, and it looks almost like a lake. This has to do with how the radar signal reacts to different surfaces: areas where the radar signal is absorbed appear darker, while areas where the signal is reflected back to the satellite appear lighter. This gives Earth observation experts an indication of how rough or smooth the surfaces area, differences in salt density or even the presence of water.
But on the whole, the Salar de Uyuni is very flat, with a surface elevation variation of less than 1 m. This makes the area ideal for calibrating satellite radar altimeters – a different kind of radar instrument that measures surface topography. The future Sentinel-3 mission will carry a radar altimeter.
The surrounding terrain is rough in comparison to the vast salt flat and is dominated by the volcanoes of the Andes mountains forming part of the Pacific Ring of Fire.
Sentinel-1A is the first in the two-satellite Sentinel-1 mission for Europe’s Copernicus program. Its radar data will be used for a variety of applications, including the surveillance of the marine environment, monitoring land-surface for motion risks, mapping for forest, water and soil management, and mapping to support humanitarian aid and crisis situations.
This image is featured on the Earth from Space video program.
An unusual view of South America and the Andes mountains, acquired by Proba-V on 23 April 2014.
A giant, geological wonder in the Sahara Desert of Mauritania is pictured in this satellite image.
The 40 km-diameter circular Richat structure is one of the geological features that is easier to observe from space than from down on the ground, and has been a familiar landmark to astronauts since the earliest missions.
Once thought to be the result of a meteor impact, researchers now believe it was caused by a large dome of molten rock uplifting and, once at the surface, being shaped by wind and water into what we see today. Concentric bands of resistant quartzite rocks form ridges, with valleys of less-resistant rock between them.
The dark area on the left is part of the Adrar plateau of sedimentary rock standing some 200 m above the surrounding desert sands. A large area covered by sand dunes – called an erg – can be seen in the lower-right part of the image, and sand is encroaching into the structure’s southern side.
Zooming in on the southern side of the bullseye, we can see individual trees and bushes as tiny dots. These follow a river-like structure that appears to have been dry when this image was acquired, a few weeks after the rainy season. Some areas to the south and east of the Richat appear to be covered with temporary lakes, which are dry for most of the year.
This image, also featured on the Earth from Space video program, was acquired on 23 November 2010 by the Advanced Visible and Near Infrared Radiometer on Japan’s ALOS satellite.
On April 28, 2014, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra spacecraft acquired this image of Ubinas volcano in the Peruvian Andes. The appearance of a new lava dome in March 2014 and frequent ash emissions are signs of increasing activity at this volcano. The left image depicts vegetation in red, and shows a gray plume streaming south from the summit caldera. The right image is a combination of ASTER thermal infrared bands, highlighting the ash-rich composition of the eruptive plume. The image covers an area of 20 by 37 miles (33 by 60 kilometers), and is located at 16.3 degrees north, 70.9 degrees west.
