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Archive for September, 2009

Human activity is sinking river deltas

Posted by edro on September 22, 2009

Hundreds of millions of people face flooding

Most of the world’s major river deltas are sinking from human activity, increasing the risk of flooding which would affect hundreds of millions of people.

According to a new study led by the University of Colorado at Boulder, “24 out of the world’s 33 major deltas are sinking and that 85 percent experienced severe flooding in recent years, resulting in the temporary submergence of roughly 100,000 square miles of land.”

About 14 percent of the world’s population, more than half a billion people who live on river deltas, will be affected.

Researchers calculated that 85% of major deltas have experienced severe flooding in the last decade, concluding that the area of flood prone zones will increase by about 50% in the next few decades as sea levels rise and more of the river deltas sink.

Media Report is included in full:

World’s River Deltas Sinking Due to Human Activity, Says New Study Led by CU-Boulder

A new study led by the University of Colorado at Boulder indicates most of the world’s low-lying river deltas are sinking from human activity, making them increasingly vulnerable to flooding from rivers and ocean storms and putting tens of millions of people at risk.

While the 2007 Intergovernmental Panel on Climate Change report concluded many river deltas are at risk from sea level rise, the new study indicates other human factors are causing deltas to sink significantly. The researchers concluded the sinking of deltas from Asia and India to the Americas is exacerbated by the upstream trapping of sediments by reservoirs and dams, man-made channels and levees that whisk sediment into the oceans beyond coastal floodplains, and the accelerated compacting of floodplain sediment caused by the extraction of groundwater and natural gas.

Figure below: An image of the Pearl River Delta in China taken by NASA’s space shuttle Endeavour during the Shuttle Radar Topography Mission in 2000. The areas below sea level are shown in purple. Image courtesy NASA, CSDMS, University of Colorado.

 Mekong & Myanmar & Pearl

The study concluded that 24 out of the world’s 33 major deltas are sinking and that 85 percent experienced severe flooding in recent years, resulting in the temporary submergence of roughly 100,000 square miles of land. About 500 million people in the world live on river deltas.

Published in the Sept. 20 issue of Nature Geoscience, the study was led by CU-Boulder Professor James Syvitski, who is directing a $4.2 million effort funded by the National Science Foundation to model large-scale global processes on Earth like erosion and flooding. Known as the Community Surface Dynamic Modeling System, or CSDMS, the effort involves hundreds of scientists from dozens of federal labs and universities around the nation.

The Nature Geoscience authors predict that global delta flooding could increase by 50 percent under current projections of about 18 inches in sea level rise by the end of the century as forecast by the 2007 Intergovernmental Panel on Climate Change report. The flooding will increase even more if the capture of sediments upstream from deltas by reservoirs and other water diversion projects persists and prevents the growth and buffering of the deltas, according to the study.

“We argue that the world’s low-lying deltas are increasingly vulnerable to flooding, either from their feeding rivers or from ocean storms,” said CU-Boulder Research Associate Albert Kettner, a co-author on the study at CU-Boulder’s Institute of Arctic and Alpine Research and member of the CSDMS team. “This study shows there are a host of human-induced factors that already cause deltas to sink much more rapidly than could be explained by sea level alone.”

Other study co-authors include CU-Boulder’s Irina Overeem, Eric Hutton and Mark Hannon, G. Robert Brakenridge of Dartmouth College, John Day of Louisiana State University, Charles Vorosmarty of City College of New York, Yoshiki Saito of the Geological Survey of Japan, Liviu Giosan of the Woods Hole Oceanographic Institute and Robert Nichols of the University of Southampton in England.

The team used satellite data from NASA’s Shuttle Radar Topography Mission, which carried a bevy of radar instruments that swept more than 80 percent of Earth’s surface during a 12-day mission of the space shuttle Endeavour in 2000. The researchers compared the SRTM data with historical maps published between 1760 and 1922.

“Every year, about 10 million people are being affected by storm surges,” said CU-Boulder’s Overeem, also an INSTAAR researcher and CSDMS scientist. “Hurricane Katrina may be the best example that stands out in the United States, but flooding in the Asian deltas of Irrawaddy in Myanmar and the Ganges-Brahmaputra in India and Bangladesh have recently claimed thousands of lives as well.”

The researchers predict that similar disasters could potentially occur in the Pearl River delta in China and the Mekong River delta in Vietnam, where thousands of square miles are below sea level and the regions are hit by periodic typhoons.

“Although humans have largely mastered the everyday behaviour of lowland rivers, they seem less able to deal with the fury of storm surges that can temporarily raise sea level by three to 10 meters (10 to 33 feet),” wrote the study authors. “It remains alarming how often deltas flood, whether from land or from sea, and the trend seems to be worsening.”

“We are interested in how landscapes and seascapes change over time, and how materials like water, sediments and nutrients are transported from one place to another,” said Syvitski a geological sciences professor at CU-Boulder. “The CSDMS effort will give us a better understanding of Earth and allow us to make better predictions about areas at risk to phenomena like deforestation, forest fires, land-use changes and the impacts of climate change.”

For more information on INSTAAR visit instaar.colorado.edu/index.html. For more information on CSDMS visit csdms.colorado.edu/wiki/Main_Page.
© Regents of the University of Colorado

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New Hubble Images

Posted by edro on September 9, 2009

Cosmic Wonder Snaps

The following images taken by the recently repaired Hubble telescope were released September 9, 2009.

Colorful Stars Galore Inside Globular Star Cluster Omega Centauri hs-2009-25-q-large_web
NASA’s Hubble Space Telescope snapped this panoramic view of a colorful assortment of 100,000 stars residing in the crowded core of a giant star cluster.
The image reveals a small region inside the massive globular cluster Omega Centauri, which boasts nearly 10 million stars. Globular clusters, ancient swarms of stars united by gravity, are the homesteaders of our Milky Way galaxy. The stars in Omega Centauri are between 10 billion and 12 billion years old. The cluster lies about 16,000 light-years from Earth.

Object Name: Omega Centauri (NGC 5139)
Object Description: Globular Star Cluster
Position (J2000): R.A. 13h 26m 45s.9
Dec. -47° 28′ 37″
Constellation: Centaurus
Distance: 16,000 light-years or 4,800 parsecs
Dimensions: This image is 1.4 arcminutes (6.3 light-years or 1.9 parsecs) wide.

Jet in Carina: WFC3 UVIS Full Field
hs-2009-25-l-large_web
Full-field image of a stellar jet in the Carina Nebula, imaged by Hubble’s WFC3/UVIS detector. See bottom image for more information.

Jet in Carina: WFC3 IR
hs-2009-25-j-large_web
Hubble WFC3 image of a stellar jet in Carina, observed in infrared light.
See bottom image for more information.

Butterfly Emerges from Stellar Demise in Planetary Nebula NGC 6302
hs-2009-25-f-large_web
What resemble dainty butterfly wings are actually roiling cauldrons of gas heated to more than 36,000 degrees Fahrenheit. The gas is tearing across space at more than 600,000 miles an hour—fast enough to travel from Earth to the Moon in 24 minutes!

Object Name: NGC 6302 (Butterfly Nebula, Bug Nebula)
Object Description: Planetary Nebula
Position (J2000): R.A. 17h 13m 43s.3
Dec. -37° 06′ 10″
Constellation: Scorpius
Distance: 3,800 light-years (1,200 parsecs)
Dimensions: This image is 2.4 arcminutes (2.7 light-years or 0.8 parsecs) wide.

Galactic Wreckage in Stephan’s Quintet
hs-2009-25-c-large_web
An assortment of stars across a wide color range, from young, blue stars to aging, red stars. This portrait of Stephan’s Quintet, also known as Hickson Compact Group 92, was taken by the new Wide Field Camera 3 (WFC3) aboard NASA’s Hubble Space Telescope. Stephan’s Quintet, as the name implies, is a group of five galaxies. The name, however, is a bit of a misnomer. Studies have shown that group member NGC 7320, at upper left, is actually a foreground galaxy about seven times closer to Earth than the rest of the group.  Galaxy group Stephan’s Quintet is located in the constellation Pegasus.

Object Name:      Stephan’s Quintet (HCG 92)
Object Description:     Interacting Galaxy Group
Position (J2000):     R.A. 22h 35m 57s.51
Dec. +33° 57′ 35″.68
Constellation:     Pegasus
Distance:     Thes Quintet is 290 million light-years (90 million parsecs) away. The foreground, superposed NGC 7320 is 40 million light-years (12 million parsecs) away.
Dimensions:     This image is 4 arcminutes (345,000 light-years or 106,000 parsecs) wide.

Barred Spiral Galaxy NGC 6217
hs-2009-25-bc-large_web
This is the first image of a celestial object taken with the newly repaired Advanced Camera for Surveys (ACS). The camera was restored to operation during the STS-125 servicing mission to upgrade the Hubble Space Telescope.  The barred spiral galaxy NGC 6217 was photographed on June 13 and July 8, 2009, as part of the initial testing and calibration of Hubble’s ACS. The galaxy lies 6 million light-years away in the north circumpolar constellation Ursa Major.

Object Name:      NGC 6217
Object Description:     Barred Spiral Galaxy
Position (J2000):     R.A. 16h 32m 39s.2
Dec. +78° 11′ 53″
Constellation:     Ursa Minor
Distance:     6 million light-years or 21 million parsecs
Dimensions:     This image is 2.2 arcminutes (44,000 light-years or 13,400 parsecs) wide.


Gravitational Lensing in Galaxy Cluster Abell 370
hs-2009-25-ao-large_web
Advanced Camera for Surveys (ACS) has peered nearly 5 billion light-years away to resolve intricate details in the galaxy cluster Abell 370, one of the very first galaxy clusters where astronomers observed the phenomenon of gravitational lensing, where the warping of space by the cluster’s gravitational field distorts the light from galaxies lying far behind it. This is manifested as arcs and streaks in the picture, which are the stretched images of background galaxies.

Gravitational Lens Detail in Abell 370
hs-2009-25-aq-large_web

Object Name:     Abell 370
Object Description:     Cluster of Galaxies
Position (J2000):     R.A. 02h 39m 49s.90
Dec. -01° 34′ 26″.70
Constellation:     Cetus
Distance:     4.9 billion light-years (1.5 billion parsecs)
Dimensions:     This image is 2.4 arcminutes (3.4 million light-years or 1 million parsecs) wide.

Stars Bursting to Life in the Chaotic Carina Nebula
hs-2009-25-h-web_print
These two images of a huge pillar of star birth demonstrate how observations taken in visible and in infrared light by NASA’s Hubble Space Telescope reveal dramatically different and complementary views of an object. The pictures demonstrate one example of the broad wavelength range of the new Wide Field Camera 3 (WFC3) aboard the Hubble telescope, extending from ultraviolet to visible to infrared light.

Composed of gas and dust, the pillar resides in a tempestuous stellar nursery called the Carina Nebula, located 7,500 light-years away in the southern constellation Carina. The pair of images shows that astronomers have a much more complete view of the pillar and its contents when distinct details not seen at visible wavelengths are uncovered in near-infrared light.

The top image, taken in visible light, shows the tip of the 3-light-year-long pillar, bathed in the glow of light from hot, massive stars off the top of the image. Scorching radiation and fast winds (streams of charged particles) from these stars are sculpting the pillar and causing new stars to form within it. Streamers of gas and dust can be seen flowing off the top of the structure.

Nestled inside this dense structure are fledgling stars. They cannot be seen in this image because they are hidden by a wall of gas and dust. Although the stars themselves are invisible, one of them is providing evidence of its existence. Thin puffs of material can be seen traveling to the left and to the right of a dark notch in the center of the pillar. The matter is part of a jet produced by a young star. Farther away, on the left, the jet is visible as a grouping of small, wispy clouds. A few small clouds are visible at a similar distance on the right side of the jet. Astronomers estimate that the jet is moving at speeds of up to 850,000 miles an hour. The jet’s total length is about 10 light-years.

In the image at bottom, taken in near-infrared light, the dense column and the surrounding greenish-colored gas all but disappear. Only a faint outline of the pillar remains. By penetrating the wall of gas and dust, the infrared vision of WFC3 reveals the infant star that is probably blasting the jet. Part of the jet nearest the star is more prominent in this view. These features can be seen because infrared light, unlike visible light, can pass through the dust.

Other infant stars inside the pillar also appear to emerge. Three examples are the bright star almost directly below the jet-producing star, a fainter one to its right, and a pair of stars at the top of the pillar. Winds and radiation from some of the stars are blowing away gas from their neighborhoods, carving out large cavities that appear as faint dark holes.

Surrounding the stellar nursery is a treasure chest full of stars, most of which cannot be seen in the visible-light image because dense gas clouds veil their light. Many of them are background stars.

Object Name:      Jet in Carina
Object Description:     Stellar Jet/Young Stellar Object
Position (J2000):     R.A. 10h 43m 51s.30
Dec. -59° 55′ 21″.0
Constellation:     Carina
Distance:     7,500 light-years (2,300 parsecs)
Dimensions:     This image is 3 arcminutes (6.6 light-years or 2.0 parsecs) wide.

Images and captions [edited] courtesy of Hubble Site News Center.  Credit: NASA, ESA, and the Hubble SM4 ERO Team

Posted in Abell 370, carina nebula, dark matter, Gravitational Lensing, Jet in Carina | Tagged: , , , , , , , | 1 Comment »