Cicle del carboni

The Two-Minute Carbon Cycle

June 24th, 2011 by Holli Riebeek

In the process of researching a feature for the Earth Observatory, I always come across fascinating tidbits that just don’t quite fit into my article. For instance, there’s this great carbon calculator tool from the University of Wisconsin-Madison.

Early during the development of the recent carbon cycle feature, I heard NASA scientist Peter Griffith speak to a group of National Park rangers. Most scientists speak from slides full of data, and I fully expected Peter to do so as well. But he didn’t. He stood at the front of the group with just a banana and a piece of coal. In a matter of minutes, he demonstrated both the carbon cycle and why burning fossil fuels has such a big impact on the carbon cycle. It was a simple and powerful demonstration. At the end, he concluded that by burning fossil fuels, we move carbon from the slow, old carbon cycle to the fast, young carbon cycle.

The talk shaped the way I think about the carbon cycle. And while the analogy never made it into the article, the way he organized the ideas and his conclusion did. As I was finishing the article, a colleague shared this two-minute video Peter made based on that talk. Enjoy!

Enllaceu amb la següent adreça per veure un video explicatiu:

http://www.youtube.com/watch?feature=player_embedded&v=uStoBFtjy8U

Descobert l'animal que viu en la zona més profunda de la terra

Es tracta d'uns diminuts cucs que mesuren mig mil·límetre i habiten a entre 0,9 i 3,6 quilòmetres sota la superfície.

Un equip de científics ha detectat per primera vegada, en una mina de Sud-àfrica, organismes multicel·lulars a les capes més profundes de la biosfera terrestre.

L’estudi, publicat en l’últim número de la revista Nature, aporta una nova perspectiva sobre la riquesa i diversitat de la vida sota la superfície del planeta.

La biosfera sota l’escorça terrestre assoleix profunditats de fins a tres quilòmetres, i acull una àmplia varietat d’organismes unicel·lulars.

Fins ara, tanmateix, els científics pensaven que les criatures multicel·lulars no podien viure en aquest ambient a causa de les altes temperatures, la falta d’oxigen i d’espai que es donen en les grans profunditats.

L’equip del geòleg de la universitat de Princeton (Estats Units) Tullis Onstott ha detectat diversos cucs nemátodos, inclosa una espècie desconeguda fins ara (denominada "Halicephalobus mephisto"), entre 0,9 i 3,6 quilòmetres per sota de la superfície, en una esquerda formada per l’aigua a l’interior d’una mina.

Aquestes criatures, que mesuren al voltant de mig mil·límetre, suporten altes temperatures, es reprodueixen de manera asexuada i s’alimenten preferentment de bacteris.

Les proves del Carboni-14 indiquen que l’esquerda en la qual es van trobar els nemátodos es va formar fa entre 3.000 i 12.000 anys.

Els resultats de la investigació indiquen que els ecosistemes sota la superfície terrestre són més complexos del que s’acceptava fins ara, i poden comportar importants implicacions en la recerca de vida en altres planetes.

Font: La vanguardia

Runoff from heavy rains, combined with wave action along the coast, increased the turbidity of New Zealand’s waters when this image was acquired on April 29, 2011. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’sAqua satellite captured this view of sediment flowing in the Pacific Ocean.

The volume of sediment in the water hints at rough seas. Distinctive plumes arise from pulsing rivers, while the halo of turquoise around both islands is likely sediment swept up to the ocean surface by powerful waves. The plumes fan out and fade from tan to green and blue with water depth and distance from the shore.

Cook Strait, the narrow strip of water separating the North and South Islands of New Zealand, has a reputation for being among the world’s roughest stretches of water. The islands lie within the “Roaring Forties,” a belt of winds that circles the globe around 40 degrees south. The westerlies hit the islands side on and run into the mountain ranges. Cook Strait is the only opening for the winds, so the channel becomes something of a wind tunnel. Strong winds produce high waves, and they erode the shore as shown in the image.

However, sediment may not be causing all of the color. The waters around New Zealand are rich in nutrients, so it is likely that phytoplankton are contributing to some of the fanciful swirls in the image. Mixing currents bring nutrients to the ocean’s surface, providing a prime environment for plankton blooms. Made up of millions of tiny plant-like organisms, the blooms routinely color the ocean with broad strokes of green and blue.

Phytoplankton are important to New Zealand because the organisms are the base of the ocean food chain. In places where phytoplankton flourish, fish also gather. Commercial fishing is New Zealand’s fourth largest industry.

Ar Rub’ al Khali Sand Sea, Arabian Peninsula

The Ar Rub’ al Khali, also called the “Empty Quarter,” is a large region of sand dunes and interdune flats known as a sand sea or erg. This astronaut photograph highlights a part of the Ar Rub’ al Khali near its southeastern margin, in the Sultanate of Oman.

Large, linear reddish-brown sand dunes alternate with interdune salt flats, or sabkhas. The orientation of the linear dunes lies at a right angle to northwesterly trade winds that originate in Iraq, known as the Shamal winds.

Secondary barchan (crescent-shaped) dunes and star dunes—with crests originating from a single point and stretching in several directions—can form atop the linear dunes when southwesterly winds blow during the monsoon season (Kharif winds). The long, linear dunes begin to break up into isolated large star dunes to the northeast and east (image right). This is likely the result of wind pattern interactions and of changes in the sand supply.

The Empty Quarter covers much of the south-central portion of the Arabian Peninsula, and with an area of approximately 660,000 square kilometers, it is the largest continuous sand desert on Earth. The Empty Quarter was so named because the hyperarid climate and difficulty of travel through the dunes has long discouraged permanent settlement within the region. There is geological and archeological evidence of cooler and wetter climates and human settlements in the region in the past. This evidence includes exposed lakebed sediments, scattered stone tools, and the fossils of hippopotamus, water buffalo, and long-horned cattle.

Cloud Wakes from Juan Fernandez Islands

Two small islands produced big effects in the atmosphere off of Chile in late April 2011. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’sAqua satellite captured this natural-color image of the Juan Fernandez Islands on April 29.

Isla Alejandro Selkirk and Isla Robinson Crusoe are both volcanic islands arising from an east-west submarine ridge. The islands are barely visible in this image, but their effects on nearby clouds are obvious. Poking up from the ocean surface, the islands create obstacles to air movement, such that wind blowing over each island creates a giant V shape of cloud-free air, with the island at the base.

Isla Alejandro Selkirk appears to simply interrupt the regional cloud pattern, which resumes north of the island. But the effects of Isla Robinson Crusoe appear more complex. Close to the island, the clouds look similar lenticular clouds that formed around Amsterdam Island in December 2005.

Clouds often form in rising air, and evaporate in falling air. While moist air may produce uniform clouds, and dry air may produce no clouds, alternating layers of humid and dry air can produce lens-shaped clouds. Farther away from the island, the clouds roughly resemble von Karman vortices—paisley-like patterns created by eddies.