The White Planet: The Evolution and Future of our Frozen World is a book by three French researchers (Jean Jouzel, Claude Lorius, and Dominique Raynard) about the study of ice cores in Greenland and Antartica. The book’s primary focus is how records of the past relate to present and future climate change. While this was interesting, my primary interest in the book was to simply learn more specific details of the records of the past themselves and their implications for the age of the Earth and Biblical interpretation.
I first remembering hearing about ice cores during the 2014 Bill Nye / Ken Ham debate, where Nye pointed to ice cores that he said were over 680,000 years old, showing annual layers of melting and refreezing; this was a strong claim against the young-earth model. (Not having a good grasp of the old-earth model at the time, I didn’t understand why layers wouldn’t go back hundreds of millions of years until I read Charles Lyell for myself.) Wikipedia told me it was only an unspecified number of “upper” layers that were clearly identifiable, with the rest calculated from models; this was a much weaker claim. Additionally, Michael J. Oard at Answers In Genesis argued that multiple layers can form in one year, casting doubt on the ability to reliably count layers back in time like tree rings.
Then I was given an old-earth creationist book by J. Gene White which numbered the visible layers at 60,000 from the 1992 Greenland Ice Core Project (GRIP) and 37,900 layers from the 1993 Greenland Ice Sheet Project Two (GISP2); this was an order of magnitude lower than Nye’s claim but an order of magnitude higher than the young-earth model. White also claimed that patterns of changes in elements found in these ice layers corroborated with other unrelated measurement methods, which would render infeasible a model requiring tens or hundreds of subannual layers per year. I don’t remember where I first heard of The White Planet, but it sounded like a good resource to learn more about both the counting and the composition of these ice cores.
The book did not get more specific than claims of “tens of thousands” of visually identifiable layers. It doesn’t talk about subannual layers, but it offers reasons they believe “annual dating has been possible” both in Antarctica and Greenland. “Many of the properties of the snow – concentrations of deuterium and oxygen 18,” etc, “differs depending on whether they accumulated in the summer or the winter. Furthermore, in the summer dust particles are more abundant in the snow because the winds are more favorable at the time to their being carried to the poles: the corresponding layers diffuse more light.”
Recent layers correlate with nuclear tests. Ice has “natural beta radioactivity.” “In the spring of 1955 a peak was observed that represented the fallout from the first thermonuclear tests in March 1954.” Radioactive levels increased “up to forty times greater than the natural” level corresponding to the fallout of large nuclear explosions in 1961 and 1962, decreased during “the suspension of nuclear testing in the atmosphere in 1963-1966,” and resumed again after “a partial resumption of atmospheric tests.”
There is also correlation with volcanic eruptions. “A few layers of ash corresponding to very intense volcanic eruptions” are said to be visible to the naked eye. “The chemical composition of the ice was modified at each sufficiently large volcanic eruption, with, for example, an increase in the content of sulfates. The eruptions in the Northern Hemisphere are clearly recorded in the ice of Greenland, those of the Southern Hemisphere in the Antarctic ice. Some eruptions occurring close to the equator or in the tropics can leave traces in both the north and the south when they are very violent.” In one case, the record actually changed historical consensus about a date. “The eruption of the volcano of Santorini, in Greece” was previously believed to have “occurred in the sixteenth century; the ice in Greenland, dated year by year, place that eruption a century earlier,” which has now been “confirmed by other methods.” The ice records the major volcanic eruptions of 1783-1784 (Laki) and 1815 (Tambora) as well as identifying a previously unknown eruption of twice the magnitude of those in 1259.
“Going back further, glaciologists have developed models that enable them to calculate the thickness of successive annual layer.” These models are clearly imperfect: “We estimated that the deepest ice was about 30,000 years old but later revised that dating and now more than 40,000 years of archives are available from the first drilling at Dôme C.”
At the same time, they fully recognize these imperfections: “These glaciological models have the disadvantage of being less precise as the age increases, and it is then indispensable to have points of reference deduced from comparison with ocean records, themselves dated by orbital adjustment.”
Chemical analysis of the ice reveal isotopes of oxygen and beryllium, among others, that vary in regular patterns that span tens of thousands of layers and continue past the point of visually identifiable layers. These patterns are said to directly correlate to temperature changes and to represent changes in the amount of sunlight (insolation) different parts of the Earth receive over time, which is itself affected by slight, mathematically predictable changes in the Earth’s orbit. (Ex. The eccentricity of its orbit follows variations with periodicities of 100 and 400 thousand years. The tilt of the axis – obliquity – varies on a cycle of 41 thousand years). These variations combine to affect temperature changes of several degrees which melt or freeze enough ice to create glaciation cycles every hundred thousand years or so. Early drillings only covered one of these glaciation cycles, but later deeper drillings in other places confirmed that cycle and revealed several more, which are now believed to go back 800,000 years, when various changes in the Earth’s overall condition allowed the present ice to begin accumulating.
They closely analyze these chemical patterns, both to verify chronologies across multiple sites and to identify when the patterns are too noisy to suggest any chronology.
They refer to “perturbations” of the ice when they get close to “bedrock” that make it unusable for dating. Also, at Vostok, “there was nothing very interesting up to 3,538 meters. Then, abruptly, over a few dozen centimeters, the properties changed dramatically,” revealing the ice at that point to not have accumulated from snowfall but actually to have frozen over a lake that still existed below.
As an extra complication, there are actually “two distinct chronologies” of ice and air, since air bubbles in upper layers can circulate until they become trapped under the weight of a hundred or so layers. “Since air trapping occurs gradually, these ages are averages.”
So on the one hand, there are clearly uncertainties and difficulties in reading the ice layers as a historical record. On the other hand, the scientists seem well aware of these uncertainties and only establish chronologies with as much confidence as they believe is warranted by the clarity of the data they have. They attempt to confirm ages based on patterns of dust and chemical isotopes and whatever external records are available.
As another example, scientists believe from “radiometric methods” that there was a major volcanic eruption at Toba around 75,000 years ago, “within a few thousand years” of uncertainty. They say this is “used to verify the chronology of deep ice cores.” More explicit details are not given, but it gives the impression that as they are guesstimating the age of deeper ice based on distance and chemical patterns, they find an ash layer somewhere around the 75,000 year mark that helps pinpoint that part of the record.
It is difficult to say, without access to the original research itself, how closely the given impressions match the analyses and how precise the claimed patterns actually are. The less precise the details, the easier it is for the young-Earth model to compete with it. The more precise the details, the more elaborate the young-Earth model has to become to explain why at least a thousand layers have a pretty constant one-to-one chronology but somewhere around a few thousand layers they happen to start representing a wild post-flood accumulation phase with multiple storms of alternating dust patterns and intermittent volcanoes and changing isotopes that just happen to look exactly like it would have if the Earth actually had been going around the Sun in its slightly varying divinely ordered path for the last hundred thousand years, one intelligently orchestrated season at a time.