Sun's energy influences 1,000 years of natural climate variability

This is a composite created from three images received from MODIS instruments carried on NASA's Terra and Aqua polar orbiting satellites. 

The images were received at the Dundee Satellite Receiving Station at 1151, 1205 and 1342 UTC on 7th Jan. 2010. 

Credit: NASA

Changes in the sun's energy output may have led to marked natural climate change in Europe over the last 1000 years, according to researchers at Cardiff University.

Scientists studied seafloor sediments to determine how the temperature of the North Atlantic and its localised atmospheric circulation had altered.

Warm surface waters flowing across the North Atlantic, an extension of the Gulf Stream, and warm westerly winds are responsible for the relatively mild climate of Europe, especially in winter.

Slight changes in the transport of heat associated with these systems can led to regional climate variability, and the study findings matched historic accounts of climate change, including the notoriously severe winters of the 16th and 18th centuries which pre-date global industrialisation.

The study found that changes in the Sun's activity can have a considerable impact on the ocean-atmospheric dynamics in the North Atlantic, with potential effects on regional climate.

Predictions suggest a prolonged period of low sun activity over the next few decades, but any associated natural temperature changes will be much smaller than those created by human carbon dioxide emissions, say researchers.

The study, led by Cardiff University scientists, in collaboration with colleagues at the University of Bern, is published today in the journal Nature Geoscience.

Paola Moffa-Sanchez

Dr Paola Moffa-Sanchez, lead author from Cardiff University School of Earth and Ocean Sciences, explained: "We used seafloor sediments taken from south of Iceland to study changes in the warm surface ocean current."

"This was done by analysing the chemical composition of fossilised microorganisms that had once lived in the surface of the ocean."

"These measurements were then used to reconstruct the seawater temperature and the salinity of this key ocean current over the past 1000 years."

The results of these analyses revealed large and abrupt temperature and salinity changes in the north-flowing warm current on time-scales of several decades to centuries.

Cold ocean conditions were found to match periods of low solar energy output, corresponding to intervals of low sunspot activity observed on the surface of the sun.

Using a physics-based climate model, the authors were able to test the response of the ocean to changes in the solar output and found similar results to the data.

Ian Hall

"By using the climate model it was also possible to explore how the changes in solar output affected the surface circulation of the Atlantic Ocean," said Prof Ian Hall, a co-author of the study.

"The circulation of the surface of the Atlantic Ocean is typically tightly linked to changes in the wind patterns."

"Analysis of the atmosphere component in the climate model revealed that during periods of solar minima there was a high-pressure system located west of the British Isles."

"This feature is often referred to as atmospheric blocking, and it is called this because it blocks the warm westerly winds diverting them and allowing cold Arctic air to flow south bringing harsh winters to Europe, such as those recently experienced in 2010 and 2013."

The study concludes that although the temperature changes expected from future solar activity are much smaller than the warming from human carbon dioxide emissions, regional climate variability associated with the effects of solar output on the ocean and atmosphere should be taken into account when making future climate projections.

More information: Solar forcing of North Atlantic surface temperature and salinity over the past millennium, Nature Geoscience, DOI: 10.1038/ngeo2094

NASA Terra Aqua MODIS: UK scientists reveal Amazon rainforest satellite imaging problem - Video

US Scientists have been puzzled by the apparent ‘greening up’ of the Amazon forest during its annual dry season.

However, Swansea University scientists, in research carried out in conjunction with NASA, have found that the Amazon is not as green in the dry season as researchers previously thought, because a trick of the light skews the satellite images.

The research is published in the latest issue of the scientific journal Nature; doi:10.1038/nature13006

This natural-colour satellite image shows the importance of correcting for sun-sensor geometry. 

On the left side, sunlight is backscattered by the Amazon rainforest, creating the appearance of brighter green leaves in some areas. 

To the right, sunglint makes the dark waters of the Amazon River and surrounding flooded wetlands appear silver or white compared to the darker forest. 

 Credit: NASA's Earth Observatory

The finding of the research yeam will help scientists develop a more accurate picture of changes in the Amazon, which is more important now than ever, given the enormous role the Amazon plays in regulating carbon dioxide, and influencing climate change.

NASA's Terra and Aqua satellites make daily observations over the huge expanse of Amazon forests.

The research team were investigating why previous satellite images seemed to show that the forests became greener during the dry season each year from June to October.

More greenery indicates productive, thriving vegetation, which would not be expected at a time of limited rainfall.

The new research shows that:

• The apparent greening of the Amazon in the dry season is an illusion. The forest does not become greener at all.
• It just looks that way due to a combination of shadowing within the forest canopy and the way that satellite sensors observe the Amazon during the dry season, which can create false “hot spots” in images.

Dr Jackie Rosette

‌Swansea researchers, working with NASA, developed a mathematical model which predicts how a forest will be seen from space, and how leaf area can be measured.

One of the Swansea team, Dr Jackie Rosette, spent 2 years at Goddard Space Flight Center, working closely with NASA colleagues.

Blue colours represent areas in Amazon forests where sensors and models can overestimate the green-up of vegetation; white represents areas that lack forest cover. 

The map is based on a model that extends the sun-sensor correction to all pixels in the southern Amazon. 

Credit: Doug Morton and NASA's Earth Observatory

Professor Peter North from the Department of Geography at Swansea University, one of the authors of the research paper, said:

"The Amazon is so vast that it’s only from space that we can properly observe it, so it’s very important that the satellite data gives us as accurate a picture as possible.

Our model has helped to identify the flaws in the previous interpretation. As a result, we can be much more confident that what we are seeing is a real pattern across the Amazon, not a trick of the light.

Having an accurate picture of the Amazon is essential if we are to understand its key role in shaping the climate."

Aboard the NASA satellites are sensors called MODIS (Moderate Resolution Imaging Spectroradiometer) which measure the amount of infrared light reflected from the Amazon.

Scientists use the ratio of red and near-infrared light as a measure of vegetation.

Doug Morton, NASA’s Goddard Space Flight Center said.

"We think we have uncovered the mechanism for the appearance of seasonal greening of Amazon forests – shadowing within the canopy that changes the amount of near-infrared light observed by MODIS"

The research implies that the previous hypothesis of increased productivity during dry seasons is likely to be false, and Amazon productivity may be more limited by water availability than sunlight.

This is critical for predicting the response of the Amazon to future climate change.

NASA MODIS Image: Sea Ice Off Eastern Greenland

The MODIS instrument on NASA's Aqua satellite captured this visible image of Sea Ice off eastern Greenland on October 16, 2012.

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

Terra (formerly known as EOS/AM-1) is a joint Earth observing mission within NASA's ESE (Earth Science Enterprise) program between the United States, Japan, and Canada. 

The US provided the spacecraft, the launch, and three instruments developed by NASA (CERES, MISR, MODIS). 

Japan provided ASTER and Canada MOPITT. 

The Terra spacecraft is considered the flagship of NASA's EOS (Earth Observing Satellite) program. In February 1999, the EOS/AM-1 satellite was renamed by NASA to “Terra”.

NOAA MODIS Image: Hurricane Ernesto Set to Hit Yucatan Peninsula

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this natural-colour image of Tropical Storm Ernesto around 11:35 a.m. EDT on Aug. 6, 2012.

CREDIT: NASA

Tropical Storm Ernesto has strengthened and officially become a hurricane, according to the latest update from the U.S. National Hurricane Center (NHC) and hurricane hunters who flew through the storm.

Ernesto, situated about 185 miles (295 kilometers) east of Chetumal, Mexico, is packing winds of 80 mph (130 kph), making it a Category 1 hurricane on the Saffir-Simpson scale.

A hurricane warning is in effect from Chetumal to Tulum on the east coast of the Yucatan Peninsula and the entire coast of Belize. The island of Cozumel has also been included in the warning.

The storm is expected to strengthen further before making landfall.

Hurricane Ernesto is expected to pass over the east coast of the Yucatan on Aug. 7. After it passes over the peninsula, it will emerge over the Bay of Campeche on Wednesday afternoon or evening.

Parts of the Gulf of Mexico coat of Mexico will likely experience tropical storm conditions.

Throughout the day today, the coast of Honduras may still experience tropical storm conditions.

Belize and the Yucatan are expected to see rainfall totals between 4 and 8 inches (10 and 20 centimeters) with localized areas seeing up to 12 inches (30 cm) of rain.

Storm surge is expected to raise sea levels by 2 to 4 feet (0.6 to 1.2 meters) above normal tide levels in some areas and will be accompanied by "large and dangerous waves," the NHC warned in its forecast.

Ernest is the second hurricane of the 2012 Atlantic hurricane season. Hurricane Chris was the first.

Ernesto is also the fifth named storm of the hurricane season. So far there have been six named storms, a category that includes tropical storms and hurricanes.

The National Oceanic and Atmospheric Administration (NOAA) will be issuing an updated forecast for the remainder of the 2012 season on Thursday (Aug. 9). August and September are typically the busiest months of the hurricane season.

NASA Earth Observation Satellites reveal sudden Greenland ice melt

Image Credit: Reuters

Greenland's massive ice sheet has melted this month over an unusually large area, Nasa has said.

Scientists said the "unprecedented" melting took place over a larger area than has been detected in three decades of satellite observation.

Melting even occurred at Greenland's coldest and highest place, Summit station.

The thawed ice area jumped from 40% of the ice sheet to 97% in just four days from 8 July.

Although about half of Greenland's ice sheet normally melts over the summer months, the speed and scale of this year's melting surprised scientists, who described the phenomenon as "extraordinary".

Nasa said that nearly the entire ice cover of Greenland, from its thin, low-lying coastal edges to its centre, which is 3km (two miles) thick, experienced some degree of melting at its surface.

"When we see melt in places that we haven't seen before, at least in a long period of time, it makes you sit up and ask what's happening," Nasa chief scientist Waleed Abdalati said.

"It's a big signal, the meaning of which we're going to sort out for years to come."

He said that, because this Greenland-wide melting has happened before, Nasa is not yet able to determine whether this is a natural but rare event, or if it has been sparked by man-made global warming.

Scientists said they believed that much of Greenland's ice was already freezing again.

Until now, the most extensive melting seen by satellites in the past three decades was about 55% of the area.

Ice last melted at Summit station in 1889, ice core records show.

The news comes just days after Nasa satellite imagery revealed that a massive iceberg, twice the size of Manhattan, had broken off a glacier in Greenland.

"This event, combined with other natural but uncommon phenomena, such as the large calving event last week on Petermann Glacier, are part of a complex story," said Nasa's Tom Wagner.

NASA Aqua /Terra Satellite Image: Sicily and Mount Etna volcanic eruption

Mount Etna is Europe's most active volcano. Aqua captured this image of Etna erupting on Oct. 28, 2002.

The view of Earth from space has transformed our understanding of, as well as our admiration for, the planet.

The data and images collected by Earth-observing satellites have been used in thousands of scientific papers, helped us better respond to natural disasters, improved weather and climate forecasts, enlightened us about our impact on Earth and captivated us with beauty.

One of the stars of NASA's fleet of satellites is Aqua. The satellite is named for its ability to measure water vapour in the atmosphere, water in the oceans, as well as ice and snow.

When it was launched on May 4, 2002, scientists expected it to work for three to five years but its six instruments have been functioning perfectly for 10 years, gathering 29 million gigabytes of data in that time.

One of the most useful and impressive instruments aboard Aqua is the Moderate Resolution Imaging Spectroradiometer, which measures visible and infrared radiation, and produces truly amazing, incredibly beautiful images of Earth.

With funding for Earth-observing satellites on the decline, let's hope Aqua keeps going for 10 more years.

NASA Aqua /Terra Satellite Image: Hurricane Emilia in Eastern Pacific Ocean

NASA's Terra satellite captured this visible image of Hurricane Emilia following Tropical Storm Daniel in the Eastern Pacific Ocean on July 9, 2012 at 1825 UTC / 2:25 p.m. EDT.

Credit: NASA MODIS Rapid Response Team

NASA's Aqua satellite got a cold stare from Emilia. Infrared satellite data revealed that cloud top temperatures around Hurricane Emilia's eye were bitter cold.

The Atmospheric Infrared Sounder (AIRS) instrument that flies onboard NASA's Aqua satellite measured cloud top temperatures in the powerful thunderstorms surrounding Emilia's eye to be colder than -94 Fahrenheit (-70 Celsius).

That indicates that they're very high in the troposphere, and very powerful (which would coincide with Emilia being a major hurricane).

NASA's Terra satellite captured a visible image of Hurricane Emilia on July 9, 2012 at 1825 UTC / 2:25 p.m. EDT, and Emilia's eye was clearly visible in the image.

Emilia exploded from a Category 2 hurricane to a Category 4 hurricane on the Saffir-Simpson Scale since yesterday.

Today, July 10 at 5 a.m. EDT, Emilia's maximum sustained winds were near 140 mph (220 kmh). By 11 a.m. EDT, Emilia's maximum sustained winds dropped to 130 mph (215 kmh),still holding to Category 4 hurricane status.

Emilia was located about 685 miles (1100 km) south-southwest of the southern tip of Baja California. Emilia is moving at 10 mph (17 kmh) to the west-northwest.

The National Hurricane Center expects Emilia to continue weakening tonight through Thursday, July 12.

Behind Emilia to the east, lies System 98E, a tropical low pressure area that appears to be developing. The National Hurricane Center gives System 98E a 40 percent chance for development over the next couple of days.

That means that while Emilia is chasing Tropical Storm Daniel (west of Emilia), there may be another named storm chasing Emilia in the next couple of days.

NASA MODIS Image: Winter Storm in the Pacific Northwest

The image is a false-colour scene that better distinguishes between snow and clouds. The Ice and snow appear red.


A severe winter storm pummeled the Pacific Northwest in January late 2012, icing roads, downing power lines, and prompting avalanche warnings.

On January 20, more than 250,000 customers were without electricity, as utility crews struggled to restore power, news sources said.

Rising temperatures and potential new rainfall raised the possibility of flooding in the days that followed.

Snow still blanketed much of Washington state on January 23, 2012, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured these images.

Liquid-water clouds are white, and ice clouds are peach. Vegetation is bright green.

Snow blankets the region east of Seattle and Portland, stretching all the way to the Idaho border. In the band of forest along the Pacific Coast, snow may be more prevalent than it appears, as it is sometimes hidden from satellite imagers by trees.

Warmer air blew into the region soon after the storm, adding to hazardous conditions. Flooding closed roads and forced some residents into emergency shelters.

On January 23, KVAL reported that a fresh storm was approaching the region and might drop several inches of rain.

The National Weather Service issued a flood warning for the Portland area, as the new round of rain had the potential to push rivers into flood stage.

NASA MODIS Image Tropical Cyclone Heidi: Natural Hazards

On January 11, 2012, Tropical Cyclone Heidi was located roughly 45 nautical miles (85 kilometers) from Port Hedland, Australia.

The U.S. Navy’s Joint Typhoon Warning Center (JTWC) reported that Heidi packed maximum sustained winds of 55 knots (100 kilometers per hour) with gusts up to 70 knots (130 kilometers per hour).

The storm was moving toward the south-southwest.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this natural-color image on January 11, 2012.

The center of the storm is north-northeast of Port Hedland, and storm clouds extended over much of the northwestern Australia coast.

The JTWC forecast that Heidi would make landfall slightly west of Port Hedland. The Sydney Morning Herald reported that flooding was expected overnight January 11–12, and that residents of low-lying areas should relocate to emergency shelters.

References

1. Joint Typhoon Warning Center. (2012, January 11). Tropical Cyclone 06S (Heidi) Warning. Accessed January 11, 2012.
2. Australian Associated Press. (2012, January 12). Cyclone Heidi upgraded to Category 2. Accessed January 11, 2012.
3. Evans, N. (2012, January 11). Cyclone Heidi shuts down Port Hedland port, mines and cancels flights. PerthNow. Accessed January 11, 2012.

NASA image courtesy Jeff Schmaltz, LANCE/EOSDIS MODIS Rapid Response Team at NASA GSFC. Caption by Michon Scott.

NASA MODIS Image: New Island forming in Red Sea

An eruption occurred in the Red Sea in December 2011. According to news reports, fishermen witnessed lava fountains reaching up to 30 meters (90 feet) tall on December 19.


The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra and Aqua satellites observed plumes on December 20 and December 22.

Meanwhile, the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite detected elevated levels of sulphur dioxide, further indicating an eruption.

The activity in the Red Sea included more than an eruption. By December 23, 2011, what looked like a new island appeared in the region.

The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured these high-resolution, natural-color images on December 23, 2011 (top), and October 24, 2007 (bottom).

The image from December 2011 shows an apparent island where there had previously been an unbroken water surface.

A thick plume rises from the island, dark near the bottom and light near the top, perhaps a mixture of volcanic ash and water vapor.

The volcanic activity occurred along the Zubair Group, a collection of small islands off the west coast of Yemen.

Running in a roughly northwest-southeast line, the islands poke above the sea surface, rising from a shield volcano. This region is part of the Red Sea Rift where the African and Arabian tectonic plates pull apart and new ocean crust regularly forms.

1. References

2. Bauwens, J. (2011, December 22). Eruption in the Zubair Archipelago, in the southern Red Sea. Accessed December 27, 2011.
3. Gass, I.G., Mallick, D.I.J., Cox, K.G. (1973). Volcanic islands of the Red Sea. Journal of the Geological Society, 129(3), 275–309.
4. Global Volcanism Program. (2011, December 20). Weekly volcanic report, 14 December–20 December 2011. Smithsonian Institution. Accessed December 27, 2011.
5. Global Volcanism Program. Zubair Group. Smithsonian Institution. Accessed December 27, 2011.
6. Klemetti, E. (2011, December 19). Potential eruption off the coast of Yemen. Eruptions. Accessed December 27, 2011.
7. U.S. Geological Survey, National Park Service. (1999, January 14). Divergent plate boundaries. Accessed December 27, 2011.
8. Volcano Discovery. (2011, December 21). Volcanic eruption in the Red Sea (Yemen) reported. Accessed December 27, 2011.

NASA Earth Observatory image created by Jesse Allen, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Caption by Michon Scott.

NASA Terra Aqua MODIS images: Volcano Kizimen Spews Fresh Ash Clouds

Kizimen, an isolated stratovolcano on Russia’s Kamchatka Peninsula, spewed ash nearly 10 kilometers (32,800 feet) into the air in mid-December 2011.

Seismic activity and thermal anomalies increased near the volcano in early December, culminating in a fresh eruption starting on December 13. Kizimen has been erupting sporadically since 2009.

The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA’s Terra and Aqua satellites captured these natural-color images on December 14, 2011.

Terra passed over far eastern Russia first, at 11:05 a.m. local time, with Aqua following one hour and 50 minutes later. The time difference afforded a view of the movement of the ash plume as it blew to the south and east.

Observers with the Kamchatkan Volcanic Eruption Response Team detected lava flows and pyroclastic flows (hot avalanches of rock, ash, and water debris) on the eastern and northeastern flanks.

According to scientists at the Russian Academy of Sciences, air temperatures were 32 degrees Centigrade near the summit, while air temperatures in the surrounding region were –26 degrees.

Itar-Tass reported potential disruptions to air traffic in the northwest Pacific, particularly for low-flying planes, as aviators were put on the highest (red) alert for ash and debris.

The small abrasive particles in volcanic ash can get lodged in jet engines, causing engine failures. There was no threat, however, to local populations on the ground because of the remote location of Kizimen.

1. References

2. Itar-Tass News Agency (2011, December 14) Kamchatka’s Kizimen volcano erupting ash columns to height of more than 7 km. Accessed December 16, 2011.
3. Kamchatkan Volcanic Eruption Response Team (2011, December 16) KVERT Information Releases. Accessed December 16, 2011.
4. Smithsonian/U.S. Geological Survey Global Volcanism Program (n.d.) Kizimen. Accessed December 16, 2011.
5. Smithsonian/U.S. Geological Survey Global Volcanism Program (2011, December 13) Weekly Volcanic Activity Report. Accessed December 16, 2011.
6. Voice of Russia (2011, December 15) Kizimen volcano spewing ashes. Accessed December 16, 2011.

NASA image by Jeff Schmaltz, LANCE/EOSDIS MODIS Rapid Response. Caption by Michael Carlowicz.

NASA Terra's MODIS: Sunny Skies over Arctic Sea Ice

Clear skies allowed the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite a largely unobstructed view of the Arctic in early July 2011.

This scene is a mosaic of observations acquired by MODIS on July 11, 2011. This natural-colour mosaic shows Arctic sea ice and the brilliant white ice cap on Greenland.

High-pressure weather systems tend to bring sunny skies and high temperatures. The National Snow and Ice Data Center (NSIDC) reported that a high-pressure system occurred over the central Arctic and the Beaufort Sea in June, and high-pressure conditions persisted over the Beaufort Sea in the first half of July.

Over the North Pole, and the Laptev and East Siberian Seas, temperatures were higher than normal in the first half of July, although they were lower than normal over the Kara Sea.

The same tilt in Earth’s axis that brings about seasonal changes also brings the Arctic maximum sunlight around late June and early July. When clear skies persist over the region at the same time, this can reinforce summertime sea ice melt.

In parts of the Arctic, spring sea ice melt began earlier than usual, NSIDC stated.

On July 18, 2011, NSIDC reported that Arctic sea ice had declined at a rapid pace during the first half of July, and is currently tracking below the trend line for 2007. In September 2007, Arctic sea ice set a record low. Whether 2011 will set a new record, however, is yet to be seen.

The large version of this image has a resolution of 1 kilometer.

Flooding from Tsunami near Sendai, Japan : NASA Modis Natural Hazards

NASA’s Terra satellite’s first view of northeastern Japan in the wake of a devastating earthquake and tsunami reveal extensive flooding along the coast.

The Moderate Resolution Imaging Spectroradiometer (MODIS) acquired the top image of the Sendai region on March 12, 2011, at 10:30 a.m.

The lower image, taken by Terra MODIS on February 26, 2011, is provided as a point of reference.
Water is black or dark blue in these images.

It is difficult to see the coastline in the March 12 image, but a thin green line outlines the shore.

This green line is higher-elevation land that is above water, presumably preventing the flood of water from returning to the sea.

The flood indicator on the lower image illustrates how far inland the flood extends.
Both images were made with infrared and visible light, a combination that increases the contrast between muddy water and land. Plant-covered land is green, while snow-covered land is pale blue. Clouds are white and pale blue. The paved surfaces in the city of Sendai colours it brown.
MODIS detected a fire burning near the shore north of Sendai. The fire is marked with a red box. It is also surrounded by floods.
The photo-like true-color image acquired a few hours later shows plumes of sediment washed into the ocean along the coast and a dark plume of smoke near Sendai. Both images are from the MODIS Rapid Response System, which provides twice-daily images of Japan.

NASA Terra Image: Mount Merapi volcanic ash

The volcanic eruption at Mount Merapi is pictured in this NASA Terra satellite image.

The Indonesian volcano erupted with renewed ferocity on Friday, bringing the total death toll to over 100 and blanketing the area with white ash

NASA Aster Image: Susitna Glacier, Alaska

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 August 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.

A photograph taken by researchers from the U.S. Geological Survey (archived by the National Snow and Ice Data Center) shows an equally complicated Susitna Glacier in 1970, with dirt-free and dirt-encrusted surfaces forming stripes, curves, and U-turns.

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.


References

1. Crone, A.J., et al. (2004). The Susitna Glacier thrust fault: Characteristics of surface ruptures on the fault that initiated the 2002 Denali Fault earthquake. Bulletin of the Seismological Society of America, 94(6B), S5–S22.

NASA MODIS Terra sattelite pictures of the Arctic

A satellite image shows the impact of the negative Arctic Oscillation on land surface temperatures throughout the Northern Hemisphere as observed by MODIS on NASA's Terra satellite during December 2009.

While much of the Northern Hemisphere has shivered in a cold snap in recent weeks, temperatures in the Arctic soared to unusually high levels

Picture: NASA / REUTERS

NASA: Modis Terra satellite picture of Cuba

Wisps of smoke from a few fires scattered throughout Cuba are seen in this image captured by the MODIS on NASA's Terra satellite

Picture: AFP/GETTY / NASA