Starship Asterisk*

http://earthobservatory.nasa.gov/IOTD/view.php?id=46472 wrote:

Water storage in from July 2009 through June 2010

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<<Water moves continuously between the atmosphere, ocean, and land. In much of the world, the differences in seasonal precipitation—and in how and where that water gets stored on land—are big enough to affect Earth’s local gravity field.

These maps show changes in water storage in the Western Hemisphere from July 2009 through June 2010; that is, they show how much more or less water is tied up in lakes and rivers, groundwater aquifers, soil moisture, snow, and glaciers. The measurements were made by the Gravity Recovery and Climate Experiment (GRACE), twin satellites that measure subtle changes in Earth's gravity over time. In this case, the satellites measured how Earth's gravity field changed as water piled up or was depleted from different regions at different times of year.

Though it is distributed over the landscape, water has mass; the greater the mass, the greater the gravitational attraction. Blues indicate increases above the normal water storage (mass) for an area, while browns indicate decreases. Water storage changes are measured in centimeters because they are, according to NASA hydrologist Matt Rodell, “expressed as an equivalent water level change, as if all the land's water were ponded on the surface.”

The differences in water storage are most obvious in South America. The Amazon basin receives significantly more water during the rainy season, so the equivalent height (or mass) of water is greater. The Amazon gets more rainfall than any other river basin in the world, and the seasonal water cycle is so strong that seasonal changes in North America, for instance, look small by comparison.>>

http://earthobservatory.nasa.gov/IOTD/view.php?id=47693 wrote:

Click to view full size image 1 or image 2

<<Widespread, severe drought gripped much of the Amazon Basin in 2010, straining the network of water that makes up the Amazon River. By December 3, one of the Amazon’s largest tributaries, the Negro River, reached a record-low 13.63 meters at the port in Manaus. These images, taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, illustrate the extent of the change in the river system.

[Image 1] is from December 10, 2010, while the lower [Image 2] was taken on December 9, 2008. The images include both infrared and visible light in a combination that highlights the presence of water of the ground. Clear water is black, while sediment-laden water, such as the Amazon River, is dark blue. Clouds are pale blue and plant-covered land is green. The city of Manaus is light tan.

The Negro River is significantly smaller in 2010 than in 2008. The most notable difference is in the braided channels northwest of Manaus. Many of the channels disappeared in 2010, and all are shrunken. The main body of the river near Manaus is narrower. Every body of water in the scene, including the Amazon River, also changed. Tan islands dot the Amazon where water had been in 2008. According to news reports, the drop in the water level stranded villages that rely on the rivers for transportation and caused food and water shortages. The record low at the Negro River comes just 16 months after the river set a record high of 29.77 meters, flooding Manaus.

The 2010 drought occurred on the heels of a similar “once-in-a-century” drought in 2005. In both cases, the dry weather was connected to water temperatures in the tropical Atlantic Ocean, which were much warmer than normal through most of 2010. The warm water altered weather patterns, pulling rain to the north and keeping the Amazon dry. Low humidity and high temperatures accompanied the drought, leading to extensive fires and poor air quality.>>

Céline Richard wrote:Other pictures from the same website: http://www.ushuaia.com/photo/phenomenes ... 04203.html

You can read "Before"="Avant" and "After"="Après"; that's impressing

Céline

abstract:

The montane circulation on Kilimanjaro, Tanzania and its relevance for the summit ice fields: Comparison of surface mountain climate with equivalent reanalysis parameters

N.C. Pepina, , , W.J. Duaneb and D.R. Hardyc

BMAONE23 wrote: These images arent necessarily PROOF of Global Warming though. (...) The most likely reason for the dramatic change in the Kilimanjaro ics cap is from deforestation causing a decrease in forest induced evaporation and subsequent air flow induced transportation of moisture upslope to replinish the cap. The ice that is there is then allowed to sublimate at temperatures still below freezing but isn't then replinished.

owlice wrote:
Avon River.JPG

http://antwrp.gsfc.nasa.gov/apod/ap070116.html wrote: .
<<What caused this mess? Some type of star exploded to create the
unusually shaped nebula known as Kepler's supernova remnant, but which
type? Light from the stellar explosion that created this energized
cosmic cloud was first seen on planet Earth in October 1604, a mere
400 years ago. The supernova produced a bright new star in early
17th century skies within the constellation Ophiuchus. It was studied
by astronomer Johannes Kepler & his contemporaries, with out the benefit
of a telescope, as they searched for an explanation of the heavenly
apparition. Armed with a modern understanding of stellar evolution,
early 21st century astronomers continue to explore the expanding debris
cloud, but can now use orbiting space telescopes to survey Kepler's
supernova remnant (SNR) across the spectrum. Recent X-ray data
and images of Kepler's supernova remnant taken by the orbiting
Chandra X-ray Observatory has shown relative elemental
abundances more typical of a Type Ia supernova,
indicating that the progenitor was a white dwarf star
that exploded when it accreted too much material and went over
Chandrasekhar's limit. About 13,000 light years away, Kepler's
supernova represents the most recent stellar explosion seen
to occur within our Milky Way galaxy.>>

Our view of the Solar System has changed utterly in the last fifty years. Mention that at a cocktail party and your listener will assume you’re talking about Pluto, the demotion of which has stirred more response than any other recent planetary news. But in addition to all we’ve learned through our spacecraft, our view of the Solar System has gone from a small number of orbiting planets to huge numbers of objects at vast distances. Fifty years ago, a Kuiper Belt many times more massive than the main asteroid belt was only theory. And the early Solar System models I grew up with never included any representation of a vast cloud of comets all the way out to 50,000 AU.

We’ve also begun to learn that liquid water, once thought confined to the Earth, may be plentiful throughout the system. Caleb Scharf goes to work on this in a recent post in Life Unbounded, noting what our models are telling us about internal oceans on a variety of objects:

Much can be done with purely theoretical models that seek to determine the appropriate hydrostatic balance between an object’s own gravity and its internal pressure forces – be they from gaseous, liquid, or solid states of matter. Thermal energy from formation, and critically from radiogenic heating (radioactive decay of natural isotopes), all play a role. Throw in a few actual datapoints, measurements of places like Europa or Titan, and these models get much better calibrated. The intriguing thing is that one can play around with compositions and the internal layering of material in a planet-like body to find the best looking fit. As a consequence the nature and extent of any subsurface zones of liquid water can be estimated.

Detecting Interior Oceans

The numbers get to be striking, as Hauke Hussmann and colleagues show in a 2006 paper in Icarus. Start with Galileo, the mission to Jupiter that brought home how much we needed to modify our view of the giant planet’s moons. Galileo discovered secondary induced magnetic fields in the vicinity of Europa, Callisto and Ganymede, offering strong observational evidence for subsurface oceans on all three. The fields are thought to be generated by ions contained in the liquid water layer underneath the icy outer shells. Europa has, of course, become a prime target for future study re astrobiology thanks to the prospect of water combined with a possibly thin ice layer.

Triton as seen by Voyager 2 [i](Credit: NASA)[/i]

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The Hussmann paper goes on to calculate interior structure models for medium-sized icy bodies in the outer Solar System, assuming thermal equilibrium between radiogenic heat produced by the core and the loss of heat through the ice shell. Now we really start expanding the picture: The paper shows that subsurface oceans are feasible not just on the now obvious case of Europa, but also on Rhea, Titania, Oberon, Triton and Pluto. A case can also be made for the Trans-Neptunian Objects 2003 UB₃₁₃ , Sedna and 2004 DW. And note this:

For the bodies discussed here, the liquid layers are in direct contact with the rocky cores. This contrasts with subsurface oceans inside the large icy satellites like Ganymede, Callisto, or Titan, where they are enclosed between ice-I at the top and high-pressure ice layers at the bottom. The silicate–water contact would allow the highly efficient exchange of minerals and salts between the rocks and the ocean in the interiors of those medium-sized satellites.

Interestingly, given the continued examination of the moon by the Cassini spacecraft, Enceladus does not fit the Hussmann model, the paper noting that sources other than radiogenic heating would be required to sustain such an ocean, the obvious option being tidal heating. We have much to learn about Enceladus (and the paper goes into issues regarding the orbital history of the moon, and the comparison between it and Mimas, where tidal forces are much stronger). But the upshot is clear: We need more observations to confirm whether subsurface oceans are not a common phenomenon in our system’s moons and icy bodies like Trans-Neptunian Objects.

Oceans in the Outer Dark

Hussmann and colleagues assume that subsurface reservoirs on these outer worlds are located beneath a thick ice shell of more than 100 kilometers in thickness — thick enough, in fact, that there is little link between internal oceans and surface features. But study of the interaction between these internal oceans and the surrounding magnetic fields and charged particles, and the response of the objects to tides exerted by the primary, may help us to confirm whether the oceans exist. There’s work here for generations of spacecraft, but get the model right early on and we can make reasonable extrapolations about water’s ubiquity.

The paper’s model, say its authors, is not applicable to Ganymede, Callisto and Titan, but I see that Scharf’s article cites Titan as having possibly ten times the volume of Earth’s oceans in water. This is lively stuff. Quoting Scharf: “…from these bodies alone there could readily be 10 to 16 times more liquid water slurping around off-Earth than on it.” Then factor in those Trans-Neptunian Objects, add the prospect of radiogenic heating, and you wind up with at least the possibility that TNOs could be the largest source of liquid water in the entire Solar System.

Did I say our view of the Solar System has changed? This revolution continues as we push into the Kuiper Belt. New Horizons, it’s hoped, will locate a small Trans-Neptunian Object for study at some point during its journey past Pluto/Charon, but eventually we can hope for the kind of instrumentation around outer planet satellites and other objects that will help us understand their internal composition. If the prospect of internal water bears out on the kind of scales mentioned above, then we have astrobiological potential, even if faint, all the way into the Kuiper Belt.

• Icarus 185(1) 258 (Nov 2006) DOI: 10.1016/j.icarus.2006.06.005