Файл:Carbon-14 plot, showcasing 993-994 spike.jpgFig. 1: The carbon-14 spike can be seen 993-994 CE. Colored points represent a studied region around Sweden (NH0) and Japan (NH2); yellow points represent the Japanese cedar analyzed in the study.[1]
The 993–994 carbon-14 spike was a rapid 0.91% increase in carbon-14 isotope content from tree rings dated 993-994 CE.[2][3] This event was also confirmed with an associated increase of beryllium-10 in Antarctic ice core samples, supporting the hypothesis that this event was of solar origin.[2][4] There were several astronomical observations during this time that correspond with the 14C and 10Be spikes, but these texts are few and far between.[4][5][6]
In 2021, a scientific paper used the 993–994 carbon-14 spike as a benchmark in dendrochronology (tree-ring studies) to precisely determine that Vikings were present in L'Anse aux Meadows in Newfoundland exactly 1000 years prior, in 1021 AD.[7]
The solar storm hypothesis is heavily supported by several observations of aurora events from late 992 in Korea, Germany and Ireland, usually describing a red sky, presumably because of major auroras.[4][5][6] The historical observations do not completely prove the cause of the 993-994 14C spike but show evidence of a strong solar event taking place late 992, as they were recorded within a relatively short time frame.[4][6]
In the Korean Peninsula, between December 992 and January 993, a text described "heaven's gate" opening one night.[4][6]
In the Saxony region of present-day Germany in late 992, several aurora observations were made. One set of observations, recorded October 21, 992, noted that the sky reddened three times.[4] Another set of observations, made December 26, 992, mentioned a light as bright as the sun shining for an hour, then reddening the sky, before vanishing completely.[4]
In the Ulster region of present-day Ireland on December 26, 992, texts described the sky as "blood-red" and having a "fiery hue".[4]
Similar events
The 993–994 carbon-14 spike was one of only a few well-documented 14C events. There had been a considerably larger one, the 774-775 carbon-14 spike, which was around 1.7 times as strong than the 993-994 event.[2] Both events also had subsequent 10Be spikes, which further proves that they are from strong solar activity.[5]
