Icebergs coming off of a collapsed ice bridge on the Wilkins Ice Shelf in Antarctica. Credits: ESA (Annotations by A. Humbert, Münster University)
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The latest satellite images show that icebergs have begun to break away from the northern front of the Wilkins Ice Shelf – indicating that the huge shelf has become unstable. This follows the collapse three weeks ago of the ice bridge that had previously linked the Antarctic mainland to Charcot Island. On April 24, satellite data from ESA’s Envisat satellite and the German Aerospace Centre’s TerraSAR-X satellite showed that the first icebergs had started to break away from the fragile ice shelf. A very rough estimate suggests that, so far, about 700 sq km of ice has been lost from the Wilkins Ice Shelf.
Three weeks ago, the ice bridge shattered very quickly, but it is expected that the current discharge of ice will continue for some weeks. The process where portions of a glacier’s leading edge break off as icebergs into an adjacent body of water is known as “calving” and this is occurring as a result of fracture zones that have formed over the last 15 years and which turned Wilkins into a fragile and vulnerable ice shelf.
A TerraSAR-X stripmap image from 23 April 2009. The larger icebergs are bright, while smaller icebergs are capsized and appear as dark blocks. The inset shows two superimposed Envisat ASAR images from 24 and 27 April. The region outlined in red indicates the area of the TerraSAR-X image. Credits: DLR, ESA (Annotations by A. Humbert, Münster University
“The retreat of Wilkins Ice Shelf is the latest and the largest of its kind. Eight separate ice shelves along the Antarctic Peninsula have shown signs of retreat over the last few decades. There is little doubt that these changes are the result of atmospheric warming on the Antarctic Peninsula, which has been the most rapid in the Southern Hemisphere,” explained David Vaughan from the British Antarctic Survey. Map of Antarctica showing the location of the Wilkins Ice Shelf. Credit: ESA
“The changes to Wilkins Ice Shelf provide a fabulous natural laboratory that will allow us to understand how ice shelves respond to climate change and what the future will hold for the rest of Antarctica,” Vaughan commented. “The quality and frequency of images acquired by ESA satellites mean that the break-up of Wilkins Ice Shelf can be analyzed far more effectively than any previous event. For the first time, I think, we can really begin to see the processes that have brought about the demise of the ice shelf.”
However, it is still unclear how the situation will evolve, Humbert said. “We are not sure if a new stable ice front will now form between Latady Island, Petrie Ice Rises and Dorsey Island. If the connection to Latady Island is lost, the projected loss of 3370 sq km of ice might be greater – though we have no indication that this will happen in the near future.”
An Envisat Advanced Synthetic Aperture Radar (ASAR) interferogram. Credit: IREA-CNR
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If you have ever experienced an earthquake, you know that the Earth literally moves beneath your feet. And now there’s satellite data to show just how much. Scientists studying satellite radar data from ESA’s Envisat and the Italian Space Agency’s COSMO-SkyMed, have been able analyze the movement of Earth during and after a recent earthquake in central Italy. A 6.3 earthquake shook the town of L’Aquila in on April 6, 2009, and satellite data is being used to map surface deformation in the Earth that took place after the quake and the numerous aftershocks that followed.
Using Synthetic Aperture Radar (SAR) data from these satellites, scientists took two or more radar images of the same ground location and compared them. The data is precise enough to show the differences in a scale of a few millimeters between images taken before and after the quake
Combining the before and after data, the scientists created ‘interferogram’ images that appear as rainbow-colored interference patterns. A complete set of colored bands, called ‘fringes’, represents ground movement relative to the spacecraft of half a wavelength, which is 2.8 cm in the case of the Envisat.
The Envisat interferogram shows nine fringes surrounding an area where the ground moved as much as 25 cm (along a line between the satellite’s orbital position and the earthquake area). An Envisat Advanced Synthetic Aperture Radar (ASAR) interferogram. Credits: INGV
“By using available 3D ground displacements from five GPS location sites around the affected area, we were able to confirm the preliminary results obtained with Envisat data,” said Stefano Salvi from INGV’s Earthquake Remote Sensing Group.
The COSMO-SkyMed , which is a constellation of three satellites, can provide more frequent data. This means new interferograms can be calculated every few days.
The COSMO-SkyMed data together with the Envisat data and possibly radar data from other satellites will ensure a dense sampling of the ground deformation around the L’Aquila area in the next months, which could make this earthquake one of the most covered by SAR Interferometry measurements.
To ensure all scientists are able to contribute to the analysis of the earthquake, ESA is making its Earth observation dataset collected over the L’Aquila area freely accessible with an innovative fast data download mechanism. The dataset will be continuously updated with the newest Envisat acquisitions.
“We produced an interferogram just a few hours after the Envisat acquisition by combining these data with data acquired before the earthquake on 1 February. We were pleased that we were able to immediately see the pattern of the earthquake,” said Riccardo Lanari of IREA-CNR in Naples, Italy.
Hundreds of fires rage in southern Mexico, on the Yucatan Peninsula, and in northern Guatemala and northern Honduras. Image by NASAs Aqua satellite (see the super-high resolution version)
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Having just read about the deadly wildfires in Texas and Oklahoma, I was interested to see whether one of NASA’s Earth-monitoring satellites have been tracking the situation from orbit. Whether it is too early for observations to come in, or whether one of the satellites have yet to make a pass directly above the states it is unclear, but along the way I noticed a rather striking image of the Yucatan Peninsula, Central America. In the picture retrieved by NASA’s Aqua satellite are countless wildfires dotted over Mexico, Guatemala and Honduras. It looks like a combination of arson, agricultural activity and accidental blazes are gripping the region, fuelled by dry vegetation…
As tornadoes turn parts of Arkansas into “warzones”, Texas and Oklahoma are dealing with wildfires. Although these states are no stranger to fires, the continuing drought in the southern US states are causing these fires to rage over larger areas for longer periods. Southern California is also sustaining a three-year drought, and in 2008 just north of LA (where I’m located), it seemed that a week didn’t go by without smelling smoke in the air. In fact, at one point, the wildfires burned worryingly close to where I live, filling the house with smoke at 5:30am one morning. Fortunately, we were the lucky ones, but others weren’t so fortunate and fell victim to the direction of the wind, losing property and, in some tragic cases, their lives. Unfortunately, all predictions are that if 2009 is going to be as dry as last year, SoCal will bear the brunt of another round of wildfires, and hearing bad news from Texas and Oklahoma is an uneasy reminder of things to come.
However, on browsing NASA’s Earth Observatory website, it looks like our neighbours are having a hard time with wildfires too. Hundreds of fires were burning at the start of this month, but many didn’t have a natural beginning.
On viewing the imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on board the Aqua satellite, it is hard to comprehend the scale of the wildfire-affected region. MODIS can detect areas of intense heat, allowing NASA’s Earth Observatory program to pinpoint the location and scale of burning vegetation. Red spots (fires) cover southern Mexico, on the Yucatan Peninsula, and in northern Guatemala and northern Honduras and smoke hangs over Campeche Bay in the Gulf of Mexico. This scene isn’t just caused by dry weather, it is a symptom of the pressure being applied to the tropical region by human activity. Land is at a premium in these developing regions of the world, so there is a need for farmers and loggers to clear vast areas of land to economise on the dry conditions to spread the fire. November to May are particularly difficult months as this is central America’s dry season.
Conservationists are on the look-out for accidental fires, but there is always the problem of intentional fires too. As farmland becomes scarce or access to prime logging forests becomes difficult, arson becomes a huge problem.
Fortunately, modern technology is helping countries to locate fires in real-time before they have a chance to spread. MODIS data is fed into the Fire Information for Resource Management System (FIRMS) and had users in 60 countries only months after the system was set up in 2006. Land managers and conservation groups in Central America receive messages via mobile phones and email should a fire be detected in their region, so hopefully the risk of large-scale damage can be limited.
Researchers used an electron microscope to capture these images of black carbon attached to sulfate particles. The spherical structures in image A are sulfates; the arrows point to smaller chains of black carbon. Black carbon is shown in detail in image B. Image C shows fly ash, a product of coal-combustion, that's often found in association with black carbon. While black carbon absorbs radiation and contributes to warming, sulfates reflect it and tend to cool Earth. Credit: Peter Buseck, Arizona State University
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Since the 1890s, surface temperatures on Earth have risen faster in the Arctic than in other regions of the world. Usually, discussions on global warming tend to focus on greenhouse gases as the culprit for the trend. But new NASA research suggests about half the atmospheric warming measured in the Arctic is due to airborne particles called aerosols.
Aerosols are emitted by both natural and human sources. They can influence climate by reflecting or absorbing sunlight. The particles also affect climate by changing cloud properties, such as reflectivity. There is one type of aerosol that, according to the study, reductions rather than increases in its emissions seem to have promoted warming.
The research team, led by climate scientist Drew Shindell of the NASA Goddard Institute for Space Studies used a computer model to investigate how sensitive different regional climates are to changes in levels of carbon dioxide, ozone, and aerosols.
They found that Earth’s middle and high latitudes are particularly responsive to changes in aerosol levels. The model suggests aerosols likely account for 45 % or more of the warming measured in the Arctic since 1976.
Though there are several types of aerosols, previous research indicates two in particular, sulfates and black carbon, play leading roles in climate. Both are products of human activity. Sulfates, which come mainly from the burning of coal and oil, scatter sunlight and cool the air. Over the past three decades, the United States and European countries have passed clean-air laws that have halved sulfate emissions. Since the 1890s, surface temperatures have risen faster in the Arctic than in other regions of the world. In part, these rapid changes could be due to changes in aerosol levels. Clean air regulations passed in the 1970s, for example, have likely accelerated warming by diminishing the cooling effect of sulfates. Credit: Drew Shindell, Goddard Institute for Space Studies
The models showed that regions of Earth that showed the strongest responses to aerosols in the model are the same regions that have witnessed the greatest actual temperature increases since 1976, specifically the Arctic. However in the Antarctic, aerosols play less of a role.
Researchers with the NOAA, the National Oceanic and Atmospheric Administration reported in the April 3 issue of the journal Geophysical Research Letters that Arctic summers may be ice-free in as few as 30 years.
The Arctic region has seen its surface air temperatures rise by 1.5 C (2.7 F) since the mid-1970s. In the Antarctic, surface air temperature has increased about 0.35 C (0.6 F). That makes sense, Shindell said, because the Arctic is near North America and Europe, highly industrialized regions that produce most of the world’s aerosols.
“In the mid-latitudes of the Northern Hemisphere and in the Arctic, the impact of aerosols is just as strong as that of the greenhouse gases,” said Shindell. “We will have very little leverage over climate in the next couple of decades if we’re just looking at carbon dioxide. If we want to try to stop the Arctic summer sea ice from melting completely over the next few decades, we’re much better off looking at aerosols and ozone.”
Aerosols tend to be short lived, staying in the atmosphere for just days or weeks, whereas greenhouses gases can persist for centuries. Atmospheric chemists thus think the climate may respond most quickly to changes in aerosol levels.
NASA’s upcoming Glory satellite is designed to enhance current aerosol measurement capabilities to help scientists reduce uncertainties about aerosols by measuring the distribution and properties of the particles.
When Redoubt Volcano in Alaska started rumbling in January, a team of researchers from New Mexico Tech hurried to south central Alaska to deploy a series of radio sensors. When the volcano began erupting overnight on March 22 and 23, the Lightning Mapping Array started returning clear and dramatic information about the electricity created within volcanic plumes and the resulting lightning. This is the first time ever anyone has been able to record data from a volcanic eruption right from the start. “We’re getting all the data we hoped to get and a lot more,” principal investigator Dr. Ron Thomas said. “Absolutely, the quality and quantity of the data will allow us to better understand the electrical charge structure inside a volcanic plume.”
Lightning is a frequent occurance during volcanic eruptions. The Lightning Mapping array allows scientists, meteorologists and storm chasers to pierce the veil of clouds to “see” lightning as it occurs.
“With each lightning flash, we’ll be able to monitor how it moves through the clouds and where it goes,” Thomas said. “If we take all our theories about lightning created in thunderstorms, we can learn about both types of lightning.” Photo of lightning from Redoubt Volcano during its 11:20 p.m. eruption on March 27, 2009. Photo by Brentwood Higman.
Redoubt erupted explosively about 20 times in the first seven days of activity. Most volcanic eruptions have several distinct stages. In the case of Redoubt, a stage of explosive activity is followed by a second stage that includes dome-building and slow venting of ash, rock and gasses. Within the individual explosive eruptions, different phases of electrical activity are observed.
“First, we see an eruptive or explosive phase,” physics professor Paul Krehbiel said. “Electrical activity is continuous and strong. We see a lot of small electrical discharges as hot gasses come out of the volcano.”
The second phase involves the ash cloud as it drifts away from the volcano with the wind. This phase is punctuated by discrete lightning – or lightning bolts.
“After the explosion is over, there is a subsequent phase of plume lightning,” Krehbiel said. “Full-fledged lightning occurs in the cloud of ash and water both above and downwind of the volcano.”
During a week’s time, Redoubt has had several major eruptions that have produced prolific lightning, Krehbiel said.
“The lightning activity was as strong as or stronger than we have seen in large Midwestern thunderstorms,” Krehbiel said. “The radio frequency noise was so strong and continuous that people living in the area would not have been able to watch broadcast VHF television stations.” View north into the summit crater of Redoubt volcano where recent eruptions have removed a significant portion of the glacial ice. A remnant shelf of ice remains on the west (right) side of crater, and in this view, fumaroles are rising from near the ice/wall-rock contact. Image Creator: Payne, Allison
The Redoubt eruptions are not over yet. After quieting down and appearing to go into a dome-building phase, just before sunrise Saturday, April 4, the volcano blew its top in the biggest eruption so far.
Thousands of individual segments of a single lightning stroke can be mapped with the Lightning Mapping Array and later analyzed on high-end computers to reveal how lightning initiates and spreads throughout a thunderstorm … or within a volcanic plume.
“We receive radio bursts of noise generated from sparks of lightning, just like the static you hear on your car radio during a thunderstorm,” Thomas said. “We will use our sensing stations to locate the lightning and track its path.”
This data visualization from the AMSR-E instrument on the Aqua satellite show the maximum sea ice extent for 2008-09, which occurred on Feb. 28, 2009. Credit: NASA Goddard's Scientific Visualization Studio
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The latest satellite observations of sea ice in the Arctic shows the ice cover appears to be shrinking: the ice cap is getting smaller, and thinner as well. The ice has been receding more in the summers and not growing back to its previous size and thickness during the winters. Scientists say the ice is profoundly important, as ice is the defining characteristic for the eco-system of the Arctic region. But it is also important for the entire planet, as far as constraining the Earth’s heat budget, and affecting ocean flows and planetary weather.
Arctic sea ice works like an air conditioner for the global climate system. Ice naturally cools air and water masses, plays a key role in ocean circulation, and reflects solar radiation back into space. In recent years, Arctic sea ice has been declining at a surprising rate. As ice melts it is replaced with darker sea water that absorbs more sunlight and heats up the ocean and the planet overall.
According to researchers from the National Snow and Ice Data Center in Boulder, Colo., the maximum sea ice extent for 2008-09, reached on Feb. 28, was 5.85 million square miles (15,151,430 square kilometers). That is 278,000 square miles (720,016 square kilometers) less than the average extent for 1979 to 2000. This is the fifth lowest maximum ice extent on record. The six lowest maximum events since satellite monitoring began in 1979 have all occurred in the past six years (2004-2009). Maps show the relative age of Arctic sea ice at the end of February 2009 and over time. Thin, first-year ice is the predominant type covering the Arctic Ocean this winter. Credit: From NSIDC, courtesy Chuck Fowler and Jim Maslanik, University of Colorado
Until recently, the majority of Arctic sea ice was multi-year ice, which means it survived at least one summer and often several winters. This multi-year ice is thicker and can survive longer than the seasonal ice that melts and re-freezes every year. But things have changed dramatically. According to the scientists, the thin, seasonal ice now makes up about 70 percent of the Arctic sea ice in wintertime, up from 40 to 50 percent in the 1980s and 1990s. Thicker ice, which survives two or more years, now comprises just under 10 percent of wintertime ice cover, down from 30 to 40 percent.
“9.8 percent of the ice is greater than 2 years old,” said Walt Meier, research scientist with NSIDC, at a teleconference with reporters today. “So, it’s about a third of what it used to be in terms of really old thick ice.”
Meier said the thickest and oldest ice has been on a big decline the past couple of years. “Right now, this is the lowest we’ve had,” he said. “Last year, multi-year ice made up 14 percent of the Arctic ice cap. In 2007, it was about the 25% range. That is a pretty sharp decrease. We did see some recovery in 1-2 year old ice, which is up from a low of 5 %. In theory that ice could survive, if it doesn’t get exported out of the Arctic.” The solid blue line indicates daily sea ice extent from late 2008 to early 2009. The dashed green line indicates sea ice extent in winter 2006-07 (leading up to the record-low minimum in summer 2007). The solid gray line indicates average extent from 1979 to 2000. This year’s maximum winter ice extent occurred on February 28, 2009. Credit: National Snow and Ice Data Center
Winds and ocean flows also “flushes” ice out of the Arctic region, Meier said.
Data from NASA’s Ice, Cloud, and land Elevation Satellite (ICESat) has now produced first map of sea ice thickness over the entire Arctic basin.
Ron Kwok from JPL who works with ICEsat said, “This is the first time we’ve had Arctic-wide ice thicknesses at the scale. During the 70’s and 80’s the average ice thickness was about 1.5-2 meters thicker than what we’re seeing at the current time.” Those measurements were taken using submarines and drill holes. Using ICEsat allows for the entire ice cap to be measured from space. ICEsat has been taking data for five years, and only the first two years of data (2005 and 2006) has been fully processed, but preliminary results show the decline is continuing.
During the teleconference, a journalist from northern Canada said their region has been experiencing colder winters the past couple of years, and asked if that was a good sign. “The ice is still in a precarious position,” said Meier, “and we can’t focus on short term trends of one or two years. Long terms trends show a warmer Arctic and thinner sea ice. It will take several cold years in a row to get back to where it was and to get the thick multi-year ice that can survive longer. This is not something that can be turned around in a couple of cool summers and colder winters.”
When asked if they could determine the ice depletion has come from natural or man-made causes, Meier said, “Sea ice certainly varies a lot over time, and we have fairly good records on how it has varied back to the early 1900’s, and we are confident it is much lower than it ever has been in the past half century. It’s clear the sea ice changes we are seeing go hand-in-hand with the warming planet, and the sea ice changes are entirely consistent with that. There isn’t another mechanism that could cause the long term changes we’ve seen.”
An international collaboration of astronomers is reporting an unusual spike of atmospheric particles that could be a long-sought signature of dark matter.
The orbiting PAMELA satellite, an astro physics mission operated by Italy, Russia, Germany and Sweden, has detected a glut of positrons — antimatter counterparts to electrons — in the energy range theorized to be associated with the decay of dark matter. The results appear in this week’s issue of the journal Nature.
Dark matter is the unseen substance that accounts for most of the mass of our universe, and the presence of which can be inferred from gravitational effects on visible matter. When dark matter particles are annihilated after contact with anti-matter, they should yield a variety of subatomic particles, including electrons and positrons.
Antiparticles account for a small fraction of cosmic rays and are also known to be produced in interactions between cosmic-ray nuclei and atoms in the interstellar medium, which is referred to as a ‘secondary source.”
Previous statistically limited measurements of the ratio of positron and electron fluxes have been interpreted as evidence for a primary source for the positrons, as has an increase in the total electron-positron flux at energies between 300 and 600 GeV. Primary sources could include pulsars, microquasars or dark matter annihilation.
Lead study author Oscar Adriani, an astrophysics researcher at the University of Florence in Italy, and his colleagues are reporting a positron to electron ratio that systematically increases in a way that could indicate dark matter annihilation.
The new paper reports a measurement of the positron fraction in the energy range 1.5–100GeV.
“We find that the positron fraction increases sharply over much of that range, in a way that appears to be completely inconsistent with secondary sources,” the authors wrote in the Nature paper. “We therefore conclude that a primary source, be it an astrophysical object or dark matter annihilation, is necessary.” Another feasible source for the anitmatter particles, besides dark matter annihilation, could be a pulsar, they note.
PAMELA, which stands for a Payload for Antimatter Matter Exploration and Light Nuclei Astrophysics, was launched in June 2006 and initially slated to last three years. Mission scientists now say it will continue to collect data until at least December 2009, which will help pin down whether the positrons are coming from dark matter anihilation or a single, nearby source.
Source: Nature (there is also an arXiv/astro-ph version here)
NASA image created by Jesse Allen, using EO-1 ALI data provided courtesy of the NASA EO-1 Team.
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The Red River reached a record high of 40.82 feet at Fargo, North Dakota on March 28, 2009, and flood stage for the river is 18 feet. This image, taken by the Advanced Land Imager on the Earth Observer-1 (EO-1) satellite on March 28, shows the swollen river, held in place by reinforced levees as it snakes through the region. Below you can compare images taken on March 28 and March 14 with NASA’s Aqua satellite, to show how the flooding increased between the two dates. I have a personal interest in this natural disaster, as I grew up near Fargo and have family living there. Today, with the river easing slowly down to 38 feet, the Red River Valley was hit by a blizzard of between 10-20 inches of heavy, wet snow, according to KVLY- KX4 meteorologist Mick Kjar (who happens to be my brother). So when this snow begins to melt, the river is expected to rise again.
Red River Flooding, taken March 28 by MODIS on NASA's Aqua Satelite. Red River in early March. Credit: MODIS on NASA's Aqua satellite.
The snow that covered the region in both images was both the cause of the flood and the reason that the water stopped rising. The river flooded as melting snow from a deeper-than-average snowpack filled the basin, said the National Weather Service. While the return of colder weather has helped ease the flooding, the extra snow today will cause problems when it warms up again.
The Red River made an important drop today that took some pressure off Fargo-Moorhead’s levee system. The Red is now down just below 38 feet. That’s an important threshold because Fargo’s permanent levee system is built to about 38 feet in most spots. Still, forecasters believe the river could rise again once all the snow melts, so they won’t say the threat is over.
In these images, the scene is entirely white except for the river due to snowfall. In the top image, bridges on the two main roads, Interstate 94 near the bottom and Highway 10 near the top were both closed due to flooding.
An ash cloud looms in the distance near Kachemak Bay Bluffs. Credit: Steve Baird, AVO
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Alaska’s Mount Redoubt erupted twice Thursday morning, creating a 12-mile-high cloud of ash. The Alaska Volcano Observatory reported the first eruption came about 8:30 a.m., sending an ash cloud more than 9,100 meters (30,000) feet in the air. A second eruption came about an hour later, and blasted ash 20,000 meters (65,000 feet) high. After the second eruption, mud flows called lahars near the base of the volcano ran into the nearby Drift River. The National Weather Service also issued a flash flood warning for regions surrounding the Drift River, as eruptions can cause snow and ice to melt, causing the river to swell with melt water. The ash is predicted to drift as far as Anchorage, which lies about 160 km (100 miles) northeast of the volcano.
Redoubt ash plume. NASA images created by Jesse Allen, using data provided courtesy of the MODIS Rapid Response team
The volcano erupted with five smaller blasts on Monday, but had been relatively quiet for the past two days. Since the earlier eruptions occurred during the night, satellite images were not available during the peak times of eruptions, but scientists are hoping satellites were able to capture the latest eruptions in action.
Airlines have canceled flights around the area, as ash poses a significant threat to aircraft engines. Some regions surrounding Mount Redoubt have been evacuated.
Geologists with the U.S. Geological Survey have said a lot of snow and ice remains on the mountain, increasing the danger from mud flows that already have downed hundreds of trees and carved a huge gouge out of a glacier.
Redoubt volcano crater showing rapidly melting glacier and enlarged "ice piston" feature. Picture Date: March 21, 2009 Image Creator: Cyrus Read, Image courtesy of AVO/USGS.
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Overnight, Alaska’s Redoubt volcano erupted with five large explosions. The National Weather Service has issued an Ashfall Advisory, with light ashfall already reported in some regions. Located about 100 miles southwest of Anchorage, Redoubt’s last eruption occurred in 1989-1990, causing widespread mudfalls or “lahars” and coated Anchorage and other nearby areas with ash. The ash affected air traffic as far south as Texas. Redoubt’s 3,108-meter (10,197-foot) peak has been belching steam for several weeks, with seismologists anticipating a possible eruption. Visible evidence of increased volcanic activity appeared at the alaska volcano summit from late January through February. Holes appeared in the ice, and streams of melt water cut across the surface of the Drift Glacier on Redoubt’s north flank.
The four explosions were recorded at 10:38 pm and 11:02 pm local time on March 22, and then at 2:14 am, 1:39 am and 4:37 am local time on March 23.
