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Should Fessenheim be Closed?

Wednesday, February 8, 2012 4:57:04 PM

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On 18 October 1356 an earthquake occurred near Basel in Switzerland which may have had a Mw magnitude as strong as 7.1. It destroyed the town of Basel, decimated its inhabitants, and caused much destruction in a vast region extending into France and Germany. It is the strongest earthquake to have occurred in Central Europe in recorded history. Could it happen again?

Less than 50 km north of Basel we find the oldest nuclear power station in France, at the village of Fessenheim about a km from the border with Germany. It entered into service in 1977. The concrete containment vessels that surround the reactors at Fessenheim are just a fraction of the thickness of those at the Fukushima Daiichi plant in Japan, at least one of which was shown to have cracked in the disaster there. The stations twin reactors were built about 10 m below the dike of the canal that runs alongside the Rhine River — the water serves as the station’s coolant — but France’s national utility, which runs the plant, has declined to study the consequences of a break in the embankment. I fully understand that the French ask themselves “Faut-il fermer Fessenheim ?” (Should Fessenham be Closed?). The front-runner in this year’s presidential race, Hollande, has pledged to close the plant if he is elected in May. The present president, Sarcozy won’t !

I suppose that there is no need to tell that German local authorities, and many citizens nearby, want Fessenheim closed and are angry that they have no say in the matter, despite the fact that the station sits just 1.5 km from their border. Switzerland, 40 km further south also wants Fessenham closed.

Maybe I ought to add that since its opening in 1977 the station has had no significant accidents. Does that mean that it is safe? (The design requirements for Fessenheim did certainly not specify that it must resist an (unlikely?) earthquake of magnitude 7 nearby).



The Rhine Graben is a failed rift system of Oligocene age (35.4 million to 23.3 million years ago). It is in fact the finest example of a graben I have ever seen. It formed as a response to the evolution of the Alps to the south and remains more or (I would say rather) less active to the present day. Not that the faults are very active, but a fault always remains a weak zone in the crust, where you may expect earthquakes to occur.



In French:


In Danish:




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Hot Springs in Greenland

Monday, February 6, 2012 4:01:57 PM

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Hat tip to Jón Frímann for reminding me of Greenland’s hot springs.

Hot springs in Greenland have no breaking news value. There are thousands of them, and they have been known ever since the first Scandinavians emigrated to Greenland about a thousand years ago. On the Island of Disko alone there are over 2000 hot springs. The most famous and one of the warmest of them all are however situated on the Uunartoq Island near the village of Alluitsup Paa (in my youth known as Sydprøven in Danish). Over the last 150 years it has been regularly studied by biologists, and over this period measurements at the bottom have constantly shown temperatures ranging from 40°C to 41.9°C, and there is no reason to believe that this temperature range has changed over the last thousand years. Compared with the around 800 hot springs in Iceland with an average water temperature of around 75°C this is not extremely hot - but more like warm, I would say. The difference lies in the volcanic activity in Iceland -- the Greenlandish hot springs are not related to any volcanic activity. Geothermal springs without any connections to volcanoes or hot magmas are however not at all unusual. The water issuing from a hot spring is heated by geothermal heat. In general, the temperature of rocks within the earth increases with depth. If water percolates deeply enough, it will be heated as it comes into contact with hotter rocks, The now warmer water will seek its way upwards through cracks and faults and, if still hot enough, emanate as a hot spring. The water from hot springs in non-volcanic areas is heated in this manner and such springs are known all over the world. Some authors make a distinction between hot springs with water above 37°C and warm springs with water below 37°C (normal human body temperature). There is however no universally accepted definition of a hot spring, so that a hot spring may just mean any spring with water temperatures above its surroundings. Probably the most general definition of a hot spring is that it has the same temperature all year round and is warmer than the location's average temperature.

There are ruins of a nunnery built near the hot springs on the Uunartoq Island after Greenland was Christianized, around 1000, the choice of construction site may have been related to the hot springs. The surface water is usually between 34 and 38 °C and thus well suited for bathing. That the water should contain radium and for that reason have healing properties is a myth however. Radium has never been found in the water, so if it makes you feel well it is rather because of its temperature. Gas bubbles of pure nitrogen are however rising from the bottom. The nitrogen feeds a.o. nitrogen fixating cyanobacteria, that form thick gelatinous microbial mats.

Before the second world war there were plans to utilize the hot water for various purposes, and they even started digging with the intention of building a public swimming bath, but the war made an end to that.



By the way the Greenlandic word uunartoq means something like “is warming”.





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The Empty Quarter

Friday, February 3, 2012 4:24:01 PM

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The Empty Quarter, or as it is called in Arabic, Rub' al Khali (الربع الخالي‎) is said to be the largest sand sea in the whole world. It encompasses most of the southern third of the Arabian Peninsula, including most of Saudi Arabia and areas of Oman, the United Arab Emirates, and Yemen, and covers some 650,000 km2. It holds about half as much sand as the Sahara Desert.



The desert is 1000 km long, and 500 km wide. Its surface elevation varies from 800 m in the southwest to around sea level in the northeast. The terrain is covered with sand dunes with heights of up to 250 m, interspersed with gravel and gypsum plains. As seen in above satellite image the sand is a reddish-orange color due to the presence of feldspar.

For thousands of years this territory has resisted settlement as one of the Earth's hottest, driest, and most unyielding environments - hence the name "quarter of emptiness". However oil of excellent quality has been found there and is exploited. The al-Ghawar oil field is one of the world's largest.

Dust from The Empty quarter regularly give rise to dust storms also to neighbour regions. The NASA satellite image below shows a dust storm that swept over the Arabian Peninsula in early February 2012. The image was captured on 2 February 2012. This dust storm follows a familiar pattern for this region, with especially thick dust occurring in the southwest. Toward the northeast, the dust thins enough to show the Persian Gulf, Qatar, and Bahrain.







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Arctic Sea Ice Cover and Winter Weather

Thursday, February 2, 2012 4:30:18 PM

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Climate change effects the extent of Arctic sea ice, which again effects the climate. In my cartoon below I have shown two ways in which the ice cover effects the temperature.



The albedo effect: Albedo is the fraction of solar energy (shortwave radiation) reflected from the Earth back into space. It is a measure of the reflectivity of the earth's surface. Ice, especially with snow on top of it, has a high albedo: most sunlight hitting the surface bounces back towards space. Water is much more absorbent and less reflective. So, if there is a lot of water, more solar radiation is absorbed by the ocean than when snow or ice dominates.

The lid effect: Ice cover prevents release into the atmosphere of heat stored in the ocean.

Such effects make Arctic sea ice an important component in the global climate system.

A study recently published in the scientific journal Tellus A shows that the probability of cold winters with much snow in Central Europe rises when the Arctic is covered by less sea ice in summer. A shrinking summertime sea ice cover changes the air pressure zones in the Arctic atmosphere and impacts the European winter weather.

Retreat of the light ice surface reveals the darker ocean, causing it to warm up more in summer from the solar radiation (ice-albedo feedback). The diminished ice cover can no longer prevent the heat stored in the ocean being released into the atmosphere (lid effect). As a result of the decreased sea ice cover the air is warmed more greatly than it used to be particularly in autumn and winter because during this period the ocean is warmer than the atmosphere. The warming of the air near to the ground leads to rising movements and the atmosphere becomes less stable. Winds are driven by air pressure difference between the Arctic and mid-latitudes: the so-called Arctic oscillation with the Azores highs and Iceland lows. If this difference is high, a strong westerly wind will result which in winter carries warm and humid Atlantic air masses right down to Europe (cf. the severe January storms we had in North Western Europe last month (January 2012) - January on average in fact being the most stormy in this region). If the wind does not come, cold Arctic air can penetrate down through to Europe, as was the case in the winters of 2009/2010 and 2010/2011. Model calculations show that the air pressure difference with decreased sea ice cover in the Arctic summer is weakened in the following winter, enabling Arctic cold to push down to mid-latitudes.

It must be pointed out that other factors of course also play a role. The sea ice-atmosphere relationship suggests however a potential for use in operational Northern Hemisphere seasonal forecasts.

Reference:
Jaiser et al.
Impact of sea ice cover changes on the Northern Hemisphere atmospheric winter circulation
Tellus A 2012, 64, 11595
doi:10.3402/tellusa.v64i0.11595
(NB: published under the terms of the Creative Commons Attribution-Noncommercial 3.0 Unported License -- and thus not behind a pay-wall).





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Cape Doctor

Tuesday, January 31, 2012 7:22:03 PM

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Have you seen the doctor lately. Here is one that helps keep South African Cape Town healthy - "die Kaapse dokter" in English known as "The Cape Doctor“. The Cape Doctor is the local name for a strong south-eastern wind – also known as South-Easter - that blows around Cape Town. It is said to clear all pollution (dispersing brown haze, allergens, pollutants and irritants) in the city and across the Cape Flats, offering an amazing clear sky and view of the City and its Table Mountain. Last week it also helped extinguish a fire in the Tygerberg Nature Reserve in Plattekloof. Some winds seem to have a better reputation than e.g. the Californian Santa Ana winds - that by the way aggravate fire danger.

The wind was named "die Kaapse dokter" by early settlers. it occurs regularly between October and March (the South African summer) and is not always benign. Cape winds have been responsible for 484 shipwrecks and thousands of deaths in Table bay and on the shore of the Cape peninsula over the last 500 years.



The South-Easter/”Cape Doctor“ originates from the South Atlantic High pressure system, which moves further southwards in summer as the westerlies retreat polewards. The South Atlantic High then ridges south of the country and joins up with the South Indian High pressure system often forming a band of high pressure to the south of the country during summer. Air flows anti-clockwise around a high pressure and clockwise around a low pressure in the southern hemisphere, so the resultant wind over the Western Cape in summer is mainly from the south east.





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An Ancient Black Feather

Thursday, January 26, 2012 8:07:38 PM

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A few days ago I visited a special exhibition in the natural history museum of Berlin called “Feathered Flight - 150 Years of Archaeopteryx”. The name Archaeopteryx derives from the Ancient Greek ἀρχαῖος (archaīos) meaning "ancient", and πτέρυξ (ptéryx), meaning "feather". It got its name from the first find of this rare bird/dinosaur, which was actually only a single feather found in 1860 near Solnhofen and described by Meyer in 1861.



Later fossil skeletons of the whole creature were found, and the original of the best preserved of these is on exhibition in the same natural museum of Berlin - the real thing - my picture here below is only of a mould exhibited in a museum at Solnhofen.



What the plumage looked like has been an item of discussion. Here is a a model of Archaeopteryx lithographica on display at the Oxford University Museum.

Recently it has been discovered that many feathers are preserved as melanosomes (containing light-absorbing pigments), and that the distribution of these structures in fossil feathers can preserve the colour pattern in the original feather. The discovery of preserved melanosomes opens up the possibility of interpreting the colour of extinct birds and other dinosaurs. An international team of scientists now finds that the well-preserved feather on Archaeopteryx's wing was black. The group located patches of hundreds of melanosomes encased within the fossil. The sausage-shape melanosomes were about 1 millionth of a meter long and 250 billionths of a meter wide — that is, about one-hundredth the diameter of a human hair in length and less than a wavelength of visible light in width. To determine the color of these melanosomes, researchers compared the fossilized structures with those found in 87 species of living birds that represented four classes of feathers — black, gray, brown and ones found in penguins, which have unusually large melanosomes compared with other birds. According to Ryan Carne the feather was predicted to be black with 95 percent certainty.

This all means that the Archaeopteryx lithographica might have looked a bit like this (with black feathers):



The findings were published online on 24 January 2012 in the journal Nature Communications. (The first colour study ever on an Archaeopteryx specimen)



In Danish:
http://videnskab.dk/miljo-naturvidenskab/mystisk-urfugl-havde-sorte-vinger

See also my posts:




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Talik

Wednesday, January 25, 2012 3:04:54 PM

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Taliks are found in permafrost regions. Permafrost is the easy word - it means of course permanent frost or in particular permanently frozen ground, or should I say frozen groundwater. Talik is not that easy to understand for non-russian speakers - it is derived from таять which means melt or thaw. So permafrost is permanently frozen ground, and talik is a (Russian) term for permanently unfrozen ground in regions of permafrost.



Most permafrost areas have an upper active layer that is between 1 to 3 meters thick. This layer thaws up in the summer and freezes back again in the winter. It is thus not permanently frozen. Taliks often occur underneath lakes and rivers, where the deeper water does not freeze in winter, and thus the soil underneath will not freeze either. Please bear in mind that (fresh) water has a maximum density at around 4°C, and this leads to bodies of water maintaining this temperature at their lower depths during extended periods of freezing weather (preventing the ground under the water from freezing). It is also worth to mention that salinity alters the density and freezing point of water, which may influence the formation of taliks in coastal areas. Saline water in soil freezes below 0°C, so that talik occurs below parts of the shores of the Arctic Ocean and in cold brine pockets in the ground. If the talik continuous from the surface to the area below the permafrost it is called a “through talik“. An ”open talik“ on the other hand is a pocket of unfrozen ground that is open to the ground surface but otherwise surrounded by permafrost. Unfrozen ground totally surrounded by permafrost is known as a ”closed talik“. A closed talik may for instance exist under a depression where a lake used to exist or dried out to become a bog. Closed taliks can also form where groundwater flow prevents the soil from freezing.

If the heat to prevent the soil from freezing is supplied by groundwater flowing through the talik, we have a hydrothermal talik.

If freezing is prevented by mineralised groundwater flowing through the talik, we have a hydrochemical talik.

Here are a few other more or less well defined talik terms, you may explore: ”isolated talik“, ”lateral talik“,” thermal talik“, and ”transient talik“.

Why bother? With the increasing degrading of permafrost due to global warming the formation and development of taliks have received increased interest, and taliks need to be included in models of the evolution of permafrost systems.




In German: http://www.geodz.com/deu/d/Talik



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Freshwater Bulge in the Arctic Beaufort Gyre

Monday, January 23, 2012 8:05:40 PM

ESA satellites show that a large dome of fresh water has been building up in the Arctic Ocean over the last 15 years. The sea surface in the centre of the Beaufort Gyre has risen by about 15 cm, and the volume of fresh water accumulating in this are has increased by some 8000 km3 – around 10% of all the fresh water in the Arctic Ocean. That is about 10 % of the more than 70,000 km3 of freshwater that are stored in the upper layer of the Arctic Ocean, leading to low salinities in upper-layer Arctic sea water, separated by a strong halocline from warm, saline water beneath.



The findings were published on 22 January 2012 in the online version of the scientific journal, Nature Geoscience. The dome could be a result of strong Arctic winds accelerating in the Beaufort Gyre, causing the sea surface to bulge. The freshwater itself is a result of melting ice and river runoff, and to some extent of course precipitation.

The Beaufort Gyre is an ocean and ice circulation pattern in the Beaufort Sea, north of Alaska. I have marked it with a B on the map above. This gyre moves in a clockwise direction (looking from above the North Pole). This circulation results from an average high-pressure system that spawns winds over the region. Ice that forms in or drifts into the Beaufort Gyre has historically remained in the Arctic ice system for years, accumulating snow and thickening each winter. Beginning in the late 1990s, the ice began melting away while in the southern parts of the gyre, before completing the circulation, counting for some of the increase in freshwater.

A halocline is a vertical zone in the water column in which salinity changes rapidly with depth.







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Ever heard of a Piteraq?

Tuesday, January 17, 2012 10:05:07 AM

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A Piteraq is a dreaded cold fall wind that originates on the ice cap and thunders down the East Coast of Greenland. Pitaracks are hurricane-force winds with speeds that can reach 80 m/s (288km/h). Similar winds are seen in Antarctica, where they give rise to the polar deserts known as the “Dry Valleys”.

Pitaracks often occur when there are no clouds over Greenland. The air closest to Greenland’s icecap (an icecap that rises to something like 3000 m) cools off rapidly by contact with the ice so that even in summer the air temperature might be between -20 and -30ºC, while the layer of air above it stays warm, so the temperature actually increases with height. Near the coast, air in the valleys is warmed by the sea. Gravity pulls the cooler air down into the valleys, which suddenly within minutes sets up a strong wind blowing from the west-northwest. Pitaraqs are most intense whenever a low pressure area approaches the coast. Down-slope winds flowing from high elevations of mountains, plateaus, and hills down their slopes to the valleys, planes or sea below are called katabatic winds. Katabatic is derived from the Greek, namely from καταβαινω (katabaino) - to go down. An upslope wind is called anabatic. Kata means down and ana means up.



Pitaraq weather situations are characterised by a deep blue sky, very clear and dry atmosphere and intense sunlight. Cigar-shaped clouds perpendicular to the wind direction can usually be seen towards the inland ice. Such winds show up well on satellite images in the infra-red bands, due to their higher temperature relative to the surrounding air masses. Their occurrence appears to be related to the passage of depressions, up the Denmark Strait. As the katabatic winds in Antarctica, the Pitaraq is a very dry wind.

Here is a an image captured by NASA’s Terra satellite on 20 September 2003. What looks like a streamer of snow is probably the surface of the sea reacting to the strong winds, because snow evaporates quickly in the dry arctic air. Further evidence that the streamer is on or close to the surface comes from the shadows that the clouds at sea cast on it. The threadlike structures near the coast are likely made by blowing snow or sea foam.





In Danish:




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