The first dating detail exposes circular reasoning, which occurs when one assumes a particular outcome in arguing for that same outcome. In the Greenland ice sheet, clear seasonal layers are found only in the upper parts of the cores, but in central Antarctica less snowfall and blowing snow prevent clear seasonal layering. Because ice layers become less distinct at greater depths, simply discerning deeper layers becomes more difficult. Thus, researchers usually “date” ice cores with theoretical models called “glacial flow models”—and these models assume evolutionary time [Paterson, W. S. B. 1991. Why ice-age ice is sometimes “soft.” Cold Regions Science and Technology. 20 (1): 75-98]. Not surprisingly, they yield vast ages. [Representing the anti-creation side in a recent debate, Bill Nye mentioned a 680,000-year-old Antarctic core. This number was not obtained by counting annual layers but by theoretical flow models.]
The second dating detail questions whether or not each layer represents a year. A single large storm can deposit multiple layers that might look like annual layers, and multiple dust layers may also be deposited within a single year [ Alley, R. B. et al. 1997. Visual-stratigraphic dating of the GISP2 ice core: Basis, reproducibility, and application. Journal of Geophysical Research. 102 (C12): 26367–26381]. No modern scientist watched the ice sheets form, so it’s possible that storms or phases within a storm, not whole winters, deposited many of them. This would have been especially true during the post-Flood Ice Age, a time of numerous storms and volcanic eruptions. http://www.icr.org/article/was-there-ice-age/
These two important details derail the ice-core argument for an old earth: layers are not necessarily annual, and researchers employ circular reasoning to adjust counts to fit the vast ages they expect. The volcanism during the Flood year would have warmed ocean water enough for increased evaporation and precipitation to rapidly build the ice sheets. A post-Flood ice age best explains the origin of today’s ice sheets.