Thursday, July 22, 2010

Nuclear Fallout

Since the detonation of the first nuclear device, new forms of elements have been introduced into the environment. Certain radioactive isotopes that are characteristic of nuclear fallout, previously unseen in nature, could now be detected globally. And while this sounds bad, the detection of these isotopes can act as useful and reliable markers for scientists. In other words, if we can measure these isotopes in our sample, we know that whatever it is we are measuring, dates no further back than 1945.

So say for example, you’re a billionaire and you just spent half a million dollars on wine that is said to have been owned by Thomas Jefferson. You’d probably damn well want to know whether or not you just bought yourself a couple bottles of counterfeits. Just ask bazillionaire Bill Koch, because he did just that. After purchasing the wine he grew weary of the seller’s credibility and sent the bottles off for a battery of tests. One of which included testing the bottles for traces of Ceasium-137, an isotope not naturally occurring but rather a product of nuclear fallout. After a week of tests in a detector surrounded by walls of 10in thick lead, the tests came up negative for Cs-137. The wine was at least bottled before the atomic age. But other tests for authenticity did not come back as promising…

…alright, I’ve gone off track, back to radioisotopes! Ok, they aren’t as exciting as stories about billionaires, rare wine, and deception but I shall proceed anyway. What else can radioisotopes be used for in terms of environmental science? Since we know when they first entered the atmosphere (which then takes about 10 years to equilibrate with the ocean) we can use their detection as a way to measure the patterns and rates of ocean circulation by seeing where and how far they penetrate the depth the of the water column. For example, the figure on the left shows how the concentration of bomb-produced C14 (different than naturally occurring C14) in the oceans varies with depth. The three depths, top-to-bottom, being 0, 1200 and 3500m. And what we see is very high radiocarbon in surface waters with highs around the 30° latitudes where convergent wind patterns cause the air to sink over the ocean. But as you go down with depth there is a much higher amount in the North Atlantic compared to the Pacific, and in general, the C14 is higher in the Atlantic with depth. This match up with the model scientists use to map ocean circulation, often simplified into the well known “conveyer belt model”. Seen below, the areas where deep water is formed are the North Atlantic and the Southern Ocean around Antarctica. In these areas, the surface water becomes sufficiently cold and salty that its density rises enough to make the water sink. This newly formed deep water is “young” by comparison since it has been recently re-oxygenated. This young water can then be tracked by tracers, such as radiocarbon, as it moves South. So we can determine the rate at which the currents flow and in which direction based on the concentration of our tracer. The older water, which moves sluggishly northward in the Pacific along the ocean bottom has the least amount of radiocarbon because this water has been not been near the surface for a very long time. It takes roughly a 1000 years for the ocean to turnover. So that C14-rich water in the North Atlantic, as it sinks and travels globally, it won’t see the surface again for another 1000 years.

But back to the bombs. The bombs are the reason we now have these tracers at our disposal. It’s great that along with nuclear energy, radioisotope tracers and everything else that came out of this original technology, nuclear proliferation arose out of the desire to destroy other humans. And nuclear weapons performed this task with such gusto that we are now capable to demolishing nations in the most excessive and terrifying fashion we’ve ever known. Just how many bombs were dropped in the name of testing and political posturing? Watch the video below, it starts slow, but just watch it. Every nuclear weapon detonated from 1945-1998. After the 3 minute mark, the grim horror and reality begins to onfold.

Quoting the Bad Astronomer, “what the hell were we thinking?”

The demonstrations of power between nations is clear. But to the absurd degree in which it was carried out, it appears the Cold War was nothing more than a glorified penis waving contest between the US and USSR. Probably a far more apt description would be from Carl Sagan who said "[the nuclear arms race was like] two sworn enemies standing waist deep in gasoline, one with three matches, the other with five." Sagan was an outspoken critic when it came to stockpiling of nuclear weapons and he had the ability to communicate this deathly growing and irrational problem like no other. Read the following passage from Sagan’s “The Nuclear Winter” and then watch that video again.

“Except for fools and madmen, everyone knows that nuclear war would be an unprecedented human catastrophe. A more or less typical strategic warhead has a yield of 2 megatons, the explosive equivalent of 2 million tons of TNT. But 2 million tons of TNT is about the same as all the bombs exploded in World War II -- a single bomb with the explosive power of the entire Second World War but compressed into a few seconds of time and an area 30 or 40 miles across …

In a 2-megaton explosion over a fairly large city, buildings would be vaporized, people reduced to atoms and shadows, outlying structures blown down like matchsticks and raging fires ignited. And if the bomb were exploded on the ground, an enormous crater, like those that can be seen through a telescope on the surface of the Moon, would be all that remained where midtown once had been. There are now more than 50,000 nuclear weapons, more than 13,000 megatons of yield, deployed in the arsenals of the United States and the Soviet Union -- enough to obliterate a million Hiroshimas.

But there are fewer than 3000 cities on the Earth with populations of 100,000 or more. You cannot find anything like a million Hiroshimas to obliterate. Prime military and industrial targets that are far from cities are comparatively rare. Thus, there are vastly more nuclear weapons than are needed for any plausible deterrence of a potential adversary.”

Indeed, what the hell were we thinking?

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