NASA: Tassili n’Ajjer National Park. Algeria - Astrolabe Glacier and Unbalanced Ice - 02-04-11 - Links

Posted by Ricardo Marcenaro | Posted in | Posted on 19:16


Open your mind, your heart to other cultures
Abra su mente, su corazón a otras culturas
You will be a better person
Usted será una mejor persona
RM



Tassili n’Ajjer National Park


Tassili n’Ajjer National Park


Tassili n’Ajjer National Park covers 72,000 square kilometers (27,800 square miles) in southeastern Algeria. Part of the Sahara Desert, the park has a bone-dry climate with scant rainfall, yet does not blend in with Saharan dunes. Instead, the rocky plateau rises above the surrounding sand seas. Rich in geologic and human history, Tassili n’Ajjer is a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site.
This image is made from multiple observations by the Landsat 7 satellite in the year 2000. It uses a combination of infrared, near-infrared, and visible light to better distinguish between the park’s various rock types. Sand appears in shades of yellow and tan. Granite rocks appear brick red. Blue areas are likely salts. As the patchwork of colors suggests, the geology of Tassili n’Ajjer is complex. The plateau is composed of sandstone around a mass of granite dating from the Precambrian.
Over billions of years, alternating wet and dry climates have shaped these rocks in multiple ways. Deep ravines are cut into cliff faces along the plateau’s northern margin. The ravines are remnants of ancient rivers that once flowed off the plateau into nearby lakes. Where those lakes once rippled, winds now sculpt the dunes of giant sand seas. In drier periods, winds eroded the sandstones of the plateau into “stone forests,” and natural arches. Not surprisingly, the park’s name means “plateau of chasms.”
Humans have also modified the park’s rocks. Some 15,000 engravings have so far been identified in Tassili n’Ajjer. From about 10,000 B.C. to the first few centuries A.D., successive populations also left the remains of homes and burial mounds.

  1. References

  2. Landsat Program. (2011, February 22). Tassili n’Ajjer National Park. Accessed February 28, 2011.
  3. World Heritage. (2011). Tassili n’Ajjer. UNESCO. Accessed February 28, 2011.
NASA image by Michael Taylor, Landsat Science Project Office. Caption by Michon Scott based on image interpretation by Michael Taylor.
Instrument: 
Landsat 7


Astrolabe Glacier and Unbalanced Ice

Astrolabe Glacier and Unbalanced Ice


Astrolabe Glacier and Unbalanced Ice


Located in the Terre Adélie-George V Land section of East Antarctica, Astrolabe Glacier streams out from the interior of Antarctica to dump ice into the sea. This outlet glacier is estimated to be 10 kilometers (6 miles) wide, and the drainage basin that feeds it stretches as much as 200 kilometers (120 miles) inland. Astrolabe is named for the flagship of Captain Jules Dumont d’Urville’s 19th century expedition to Antarctica.
The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this natural-color image of Astrolabe on November 28, 2010, in late austral spring. Icebergs were breaking off from the glacier tongue—which extends from the coast like a shelf over the open water of the Southern Ocean—and running into sea ice. The calving front is roughly 7 kilometers (4 miles) wide, and scientists estimate that it loses half a cubic kilometer of ice per year.
The ice calving shown in this image is not necessarily unusual for the region or the time of year. But what is unusual is how much more calving all the glaciers of Antarctica and Greenland have been doing in the past two decades.
According to a new NASA-funded satellite study, the Greenland and Antarctic ice sheets are losing mass at an accelerating pace and are overtaking ice loss from mountain glaciers and ice caps to become the dominant contributor to global sea level rise. The graph above shows the gain and loss of ice mass from the world's two largest ice sheets. Though there are gains within individual years, the overall trend from 1992 to 2010 has been toward losses.
Each year over the course of the 18-year study, the two ice sheets lost a combined average of 36.3 billion tons more than they did the year before. The Greenland ice sheet lost mass faster at an average of 21.9 billion tons more per year. In Antarctica, the year-over-year speedup in lost ice mass averaged 14.5 billion tons.
“That ice sheets will dominate future sea level rise is not surprising—they hold a lot more ice mass than mountain glaciers,” said lead author Eric Rignot, jointly of NASA’s Jet Propulsion Laboratory and the University of California, Irvine. “What is surprising is this increased contribution by the ice sheets is already happening. If present trends continue, sea level is likely to be significantly higher than levels projected by the United Nations Intergovernmental Panel on Climate Change in 2007.”
The authors conclude that, if current ice sheet melting rates continue for the next four decades, their cumulative loss could raise sea level by 15 centimeters (5.9 inches) by 2050. While this provides one indication of the potential contribution ice sheets could make to sea level in the coming century, the authors caution that considerable uncertainties remain in estimating future ice loss acceleration.

  1. References

  2. Jet Propulsion Laboratory (2011, March 8) NASA Finds Polar Ice Adding More to Rising Seas. Accessed March 25, 2011.
  3. Jet Propulsion Laboratory (n.d.) GRACE Tellus. Accessed March 25, 2011.
  4. Laboratoire de Glaciologie et Géophysique de l'Environnement, Universite Joseph Fourier (n.d.) Dynamics of coastal outlet glaciers and implications on the overall mass balance of Antarctica, Terre -Adelie Sector. Accessed March 25, 2011.
  5. University of Texas at Austin, Center for Space Research (n.d.) GRACE - Gravity Recovery and Climate Experiment. Accessed March 25, 2011.
NASA Earth Observatory image by Jesse Allen and Robert Simmon, using ALI data from the EO-1 Team. Mass balance data from Eric Rignot, JPL. Caption by Mike Carlowicz, with background from Alan Buis.
Instrument: 
EO-1 - ALI



NASA: Tassili n’Ajjer National Park. Algeria - Astrolabe Glacier and Unbalanced Ice - 02-04-11 - Links











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