Ice core dating is a scientific technique with multiple applications. It is also of value for ancient Middle Eastern chronology, but how accurate is it? Like the three types of scientific data already discussed, radiocarbon dating, astronomical dating, and dendrochronology, it is useful, but it has its drawbacks.
It might seem surprising that ice-core dating has applications in historical chronology. After all, even if scientists could precisely date annual ice layers to absolute years, they rarely find ancient artifacts in association with those layers. Therefore, its only relevance for that purpose would be if an event left evidence in one or more ice core layers and in another datable record (historical or scientific). Suppose an ancient inscription recorded the timing of a volcanic eruption and that event was also detectable in the contemporaneous ice core layer as an electrical conductivity measurement (ECM), enhanced isotope quantities (such as Beryllium-10), or tephra (volcanic ash) residue. These two completely independent sources would verify each other. Moreover, analysis of chemical, isotope, and ion concentrations in the ice, along with the tephra composition, could help identify which volcano erupted. Since volcanic residues also appear in tree rings, these sciences complement each other.
Ice core dating has one major drawback before the Common Era (CE). With one or more absolute anchor dates, astronomical dating can be exact to the year, and related relative timelines, such as accurate king list data, can extend those absolute dates by decades or even centuries. In contrast, the BCE ice cores have error ranges. Still, its accuracy during that period falls between those of astronomical and radiocarbon dating.
The Greenland ice-core chronology (GICC21), published in 2021, was a significant improvement over the earlier version, GICC05, published in 2005. The scientists behind this project compared layers of Greenland ice cores from six sites to correctly align them with one another based on their mineral and chemical contents, isotopes, dust and volcanic ash, and electrical conductivity. They also compared ice core layers with datable tree rings, yielding a small error range for GICC21 of ± 6 years around 500 BCE. For earlier periods, the range gradually increases. Although this science is valuable for ancient chronology, this imprecision means that ice-core dating is not specific enough to pinpoint the exact date of a volcanic event in the BCE period.
Ice-core analysis could potentially help verify the Thera eruption of 1650 BCE. (Its global effects began in 1649.) For that period, the GICC21 error range is ± 7.4 years. Thus, if a strong volcanic signal were to appear in the ice core layers nominally dated to 1656-1643 BCE, it would verify the approximate timing of the eruption. A robust ice core signal does appear in the nominal 1654 BCE layer. Ice-core scientists could, in theory, confirm that the eruption that produced that signal was Thera, not another. Unfortunately, the erroneous conventional chronology has influenced those scientists to the degree that they have not considered that date as plausibly related to the Thera eruption. If they could find “crypto-tephra grains” in that layer, they would almost certainly prove that the related signal was from Thera.
Fortunately, one application of ice-core dating conclusively demonstrates that the “1654 BCE” layer is from Thera. Scientists have also drilled ice cores in Antarctica and have been able to synchronize the annual layers in Antarctica and Greenland. By comparing the sizes of the two polar volcanic signals, they derive two types of valuable information: the approximate 1) magnitude of the eruption and 2) latitude of the volcano.
An article by scientists Charlotte Person et al. compared various volcanic sulfate signals. In their Table 2, they listed the bipolar asymmetry of the 1654 BCE eruption as 0.70, which roughly corresponds to the latitude of Santorini Island (36°25’N). ((0.70 x 180⁰) – 90⁰ (southern hemisphere portion) = 36⁰N. Or, with their methodology explained in the Fig. 2 caption, 38⁰24’N.) That article’s Figure 2 shows that only one bipolar ice core volcanic signal of the seventeenth and sixteenth centuries BCE was 1) of sufficient magnitude and 2) at the approximately correct latitude to be the Thera eruption, the one assigned to 1654 BCE.
Ice-core dating is not precise enough to provide year-exact results for the BCE period. Nevertheless, it yields valuable information about the approximate timing and locations of historical eruptions. The bipolar signal from “1654 BCE” further confirms the accuracy of the chronological model in The Six Pillars.