olelog

On 27 May 2009 I featured the Pacific Garbage Patch. In an article titled “Project Kaisei: voyage to clean up the plastic vortex” CNN has brought some pictures and a video from an August 2009 voyage to the area.

Apart from the CNN text, I think their dreadful images talk for themselves. The most heavily polluted areas of surface water in the gyre contained six times more plastic than plankton biomass.

A further voyage next year hopes to gather more data and move closer to a practical solution to the ever increasing problem.

• http://edition.cnn.com/2009/TECH/science/10/30/trash.vortex.kaisei/index.html
  

PS.
More footage from the Kasei project:

Hat tip “Living the Scientific Life” Blog
http://scienceblogs.com/grrlscientist/2009/10/project_kaisei_2009_intro_from.php

See also: http://scienceblogs.com/grrlscientist/2009/10/project_kaisei_scripps_oceanog.php

In the cold waters of the Southern Ocean (surrounding Antactica) iron is biolimiting (i.e. it limits plankton growth), and it has for some years been suggested that fertilising it with iron could slow global warming by enhanced phytoplankton photosynthesis that would pull large amounts of carbon dioxide from the atmosphere.

Scientists at the University of Leeds have now proved that acid in the atmosphere breaks down large particles of iron found in dust into small and extremely soluble iron nanoparticles, which are more readily used by plankton.

Water droplets in clouds generally form around dust and other particles. When clouds evaporate, as they often do naturally, the surface of the particle can become very acidic. This is especially true where the air is polluted. Paradoxically, scientists suggest that large scale industry in countries like China could be combating global warming to some extent by creating more bioavailable iron in the oceans, and therefore increasing carbon dioxide removal from the atmosphere.

The research was published in the September 2009 issue of Environmental Science and Technology under the title 'Formation for Iron Nanoparticles and Increase in Iron Reactivity in Mineral Dust during Simulated Cloud Processing'.

The research was carried out by simulating clouds in the laboratory and adding a bit of Saharan dust. The laboratory experiments have been confirmed in natural samples where such cloud processing is known to have occurred.

• http://pubs.acs.org/doi/abs/10.1021/es901294g
  
• http://www.leeds.ac.uk/news/article/138/acidic_clouds_nourish_worlds_oceans?research
  
• http://www.physorg.com/news173963676.html
  

PS:
See also http://www.abc.net.au/science/articles/2009/10/07/2707287.htm (Dust storm triggers ocean bloom)

Manganese nodules were first discovered on the ocean floor in 1803. Manganese nodules, are rock concretions on the sea bottom formed of concentric layers of iron and manganese hydroxides around a core or nucleus. Nodules lie on the seabed sediment, often partly or completely buried. They vary greatly in abundance, in some cases touching one another and covering more than 70 per cent of the bottom. They may contain up to 70% manganese, around 15% iron, and further some copper, cobalt, zinc and nickel in small proportions.

Nodule growth is extremely slow – on the order of a centimeter over several million years. Several processes are involved in the formation of nodules, including the precipitation of metals from seawater (hydrogenous), the remobilization of manganese in the water column (diagenetic), the derivation of metals from hot springs associated with volcanic activity (hydrothermal), the decomposition of basaltic debris by seawater (halmyrolitic) and the precipitation of metal hydroxides through the activity of microorganisms (biogenic). Several of these processes may operate concurrently or they may follow one another during the formation of a nodule.

Since the 1960's manganese nodules have been recognized as a potential ore source. Germany seems finally willing to do something serious about it.

Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) in Hannover, Germany, has from the International Seabed Authority received an exploration licence for 15 years in 75.000 km2 sea-bed of the Pacific Ocean between Mexico and Hawaii - in the Pacific Nodule Belt between the Clarion and Clipperton fracture zones.

German geologists recently carried out an extended research project in the Pacific. They wanted to find out how many manganese nodules there are, and where they are scattered. 24 million tons of precious metals are believed to be lying under the world’s oceans. The German geologists are trying to learn whether the nodules could be recovered from the seabed without damaging the environment, and which technology would be best suited to do that.

The Pacific nodules contain on average 15-30% manganese, 7-15% iron, 1,2% nickel, 1% copper and 0,3% cobalt. They can have a diameter of up to 50 cm and are mainly found at a depth of 4-5 km. Together they may contain thousands of billions of tons manganese.

The area between the Clarion and Clipperton fracture zones and the areas belonging to different contractors are shown on this map. (If you have difficulties with reading the small letters, I can tell you that the legend for the German area is the lowest one in the legend box.)

• http://www.deutsche-welle.de/dw/article/0,,4408892,00.html
  
• http://www.cartage.org.lb/en/themes/sciences/Earthscience/Oceanography/OceanSediments/Manganesenodules/Manganesenodules.htm
  
• http://www.springerlink.com/content/44p012947k652226/
  

In Danish:

• http://ing.dk/artikel/101514-tyskland-vil-hente-metal-i-dybhavet?utm_medium=rss&utm_campaign=nyheder
  

In German:

• http://www.bgr.bund.de/nn_324952/DE/Gemeinsames/Oeffentlichkeitsarbeit/Pressemitteilungen/BGR/bgr__081002.html
  

A team of a dozen scientists now report new in situ observations and laboratory studies of specimens of a small (diameter 2.4–7.5 cm) strikingly hexagonal form originally described from sedimented steps in a wall of the axial valley of the Mid-Atlantic Ridge (water depth 3430–3575 m) near 26°N, 45°W that appears to be identical to the iconic form Paleodictyon nodosum described as a trace fossil from Eocene flysch deposits at sites in Europe and Wales.


(This photo of Paleodictyon is from the Benkovac Stone Unit. The Late Eocene Benkovac Stone Member of the Promina Formation of northern Dalmatia, Croatia, is a thinly bedded succession of alternating carbonate sandstones and calcareous mudstones, ca. 40 m thick, exposed as a narrow, SE-trending outcrop belt near the town of Benkovac. The Eocene was an epoch from ca. 56 - 34 million years ago.)

The team has gathered enough evidence to prove that the organism represents one of the world’s oldest living fossils, perhaps the oldest. The ancestors of the creature, Paleodictyon nodosum, go back to the dawn of complex life. And the creature itself, known from fossils, was once thought to have gone extinct some 50 million years ago.

So far it has not been possible to capture one of the creatures alive. It thrives in restricted areas of Atlantic seabed. Its only visible feature consists of tiny holes arranged in six-sided pattern. Until the real creature has been caught the scientists still vigorously debate what it is. The main question is whether the hexagonal patterns are burrows or body parts, vacant residences or animal remains.

The new paper seeks no consensus on the question of whether the holes and subsurface networks represent burrows or body parts. Dr. Seilacher, who backs the burrow idea, sees the tunnels as a kind of farm where an unknown type of worm or other organism raises micro-organisms to eat, while Dr. Rona sees the holes as body parts, perhaps from a type of compressed sponge. The lack of biological clues, he said in an interview, may arise because microbial predators eat the remains after the creatures die.

Reference:
Rona et al.
Paleodictyon nodosum: A living fossil on the deep-sea floor
doi:10.1016/j.dsr2.2009.05.015
(Article in Press)

• http://www.nytimes.com/2009/08/25/science/25fossil.html
  
• http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VGC-4WD1BWS-4&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=989443494&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=900183d12bc1802d8470f85e1b961b5b
  
• http://my.opera.com/nielsol/blog/2008/11/03/tracefossils-paleodictyon
  
  

Let me concentrate myself on two deserts - the driest and the oldest in the world - the Atacama Desert in South America and the Namib Desert in Southern Africa. Unlike for instance the Gobi desert, that is so far away from the sea that the water can’t make it that far and so it falls before arriving to the desert, they are both situated next to a large ocean.

To understand why these two deserts are where they are we need a bit of elementary oceanography. I suppose the coriolis effect is more or less well known. It makes ocean currents curve to the right (clockwise) in the northern hemisphere and to the left (counter-clockwise) in the southern hemisphere. This way it forms large circular ocean currents known as gyres. This map shows the 5 largest ocean gyres in the world.

Please notice in particular the South Atlantic Subtropical Gyre and the South Pacific Subtropical Gyre. Currents flowing from equator towards the poles will be warm currents (like the Gulf Stream). Currents flowing towards the equator will be cold. Due to the ocean gyres a cold current is flowing northwards along the west coast of Chile - the cold Humboldt current (also known as Peru Current). Likewise a cold current is flowing northwards along the west coast of Namibia - the cold Benguela current.

And this leads us to what is possibly the driest place on on earth (actually another outstanding candidate for this honour is a low spot in the Lut Desert of eastern Iran). The Atacama Desert is a virtually rainless plateau in South America, extending nearly 1000 km between the Andes mountains and the Pacific Ocean. Parts of Chile's Atacama Desert haven't seen a drop of rain since record-keeping began. Here a place called Arica gets just 0.76 millimetres of rain per year. At that rate, it would take a century to fill a coffee cup (not even a tee cup for my dear British readers). The precipitation (moisture equivalent to rain) in Atacama averages less than 1 centimetre per year from fog. Measurable rainfall (more than a millimetre of rain) occurs every five to 20 years and heavy rains fall only two to four times a century. No vegetation grows here. It is what is termed ‘absolute desert’.

The desert is to a great extent created by the cold Humboldt current. A great mass of ice cold water surges out of the Antarctic Ocean and flows north along the South American continental shelf. The shallowing land forces the cold deep waters up to the sea surface where the waters may encounter warm winds that blow land-ward. The warm air cools as it moves across the cold current and the air becomes too cold to hold much moisture. No rain clouds, therefore, can reach the coast and the land dries into a hostile area for life. In the winter, fog rises from the upwelling cold currents, blankets the desert, and gives moisture to the land. The mountain ranges also play a role. The Atacama is blocked from moisture on both sides by the Andes mountains to the east and by coastal mountains to the west. The trade winds blow westward on the east side of the Andes, but the desert lies in the rain shadow of the Andes.

I would indeed like to compare the situation with the Namib Desert and the cold Benguela current in Southern Africa. The Namib Desert is considered to be the oldest desert in the world, having endured arid or semi-arid conditions for at least 55 million years. Its aridity is caused by the descent of dry air cooled by the cold Benguela current along the coast. It has less than 10 mm of rain annually and is almost completely barren. The cold waters of the north-flowing Benguela current move from the western coast of South Africa and Namibia towards north and Northwest up to the line where it joins the southern equatorial current which is a warm current. Its waters are cold because there are very deep waters that were brought upward due to the rotation of Earth from west to east. This upward movement of deep waters are sometimes increased by southern Trade winds which blow west from the Kalahari Desert towards the ocean. The cold current creates the desert conditions of the shore of Namibia, and the persistent fogs of the Skeleton Coast.

That these two deserts are both located at the same southern latitude (trade wind zone) on the west coast of a large continent is no coincidence. The Tropic of Capricorn passes through both deserts.

Deserts can, by the way, be classified by their geographical location and dominant weather pattern as trade wind, mid-latitude, rain shadow, coastal, monsoon, or polar deserts. The Atacama Desert covers three of these categories: trade wind, mid-latitude, and coastal.

This is a special post written for the the sixth Carnival of the Arid coming up soon at Coyote Crossing. I’ll give you the URL here in due time...

... and here it comes:

• http://faultline.org/index.php/site/item/carnival_of_the_arid_6/

go and enjoy it!