Less than two years later, as the graph indicates, scientists detected Chernobyl radioactivity in snow at the South Pole--a graphic reminder of how small our planet is. Distinct annual layers stand out because, in snow that falls in summer, crystals are larger and acidity higher than in winter snow. (This represents about 11,350 feet of ice accumulation.) The graph clearly shows how a rise in gases will mean a rise in global temperature (though whether rising gases trigger rising temperatures, or vice versa, remains unknown).
In cores from Antarctica and Greenland, researchers have pinpointed the beginning of atomic-bomb testing in the mid-1950s. In some cases, scientists can even tell seasons apart, by using a laser to measure the concentration of dust particles. A., 1993, Abrupt increase in Greenland snow accumulation at the end of the Younger Dryas event, 336, 552-554. Also note that (though the graph, which has data up to two decades old, does not show this), at about 360 parts per million, the amount of CO, 345, 127-131.
Using state-of-the-art cosmic ray cascade and chemistry-climate models, we successfully reproduce the observed variability of cosmogenic isotope Be, around 775 AD, in four ice cores from Greenland and Antarctica, thereby validating the models in the assessment of this event.
We add to prior conclusions that any nitrate deposition signal from SEP events remains too weak to be detected in ice cores by showing that, even for such an extreme solar storm and sub-annual data resolution, the nitrate deposition signal is indistinguishable from the seasonal cycle.
You could see what the world was like when ice sheets a thousand feet thick blanketed Canada and northern Europe, or when the Indonesian volcano Toba blew its top in the largest volcanic eruption of the last half million years. The long cylinders of ancient ice that they retrieve provide a dazzlingly detailed record of what was happening in the world over the past several ice ages. (The seemingly larger spike at about 53,000 years ago involved a series of smaller eruptions on Iceland, which is far closer than Toba is to Greenland, where this core was taken.) Such violent, so-called caldera eruptions can drastically alter global climate, by spewing so much ash and sulfur compounds into the atmosphere as to block sunlight and lower temperatures worldwide.
This technique does not give specific ages to items.
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Using cosmogenic isotopic analyses of less than two dozen samples, Mackintosh et al. 551–554]) lift the veil of suspicion that has hung over the East Antarctic Ice Sheet.
In two short decades, we have learned so much about when glaciers and ice sheets retreated that it's hard to imagine a world where glacial boulders were not targets for dating.
Yet, children born when the first paper using cosmogenic nuclides to date such erratics was published (Phillips et al., 1990) are still not old enough to vote. took a simple and oft-used approach for characterizing the vertical extent of now-vanished ice.