Ice carbon dating
Our experimental methods and sampling strategy are validated by (Kr ages due to past geomagnetic variability to be below 3 ka.We show that ice from the previous interglacial period (Marine Isotope Stage 5e, 130–115 ka before present) can be found in abundance near the surface of Taylor Glacier.Finally, in contrast to Kr dating of ice gave inconclusive results owing to ∼50% gas loss and substantial but poorly quantified (≥20%) contamination with modern air (35).The single sample in that study was extracted by chainsaw from the surface of the Allan Hills BIA site in Antarctica, and the sample quality was compromised by “extensive fracturing of the highly strained ice” (ref. In addition, a reliable method for Kr radiometric dating of polar ice using air extracted from four ice samples from the Taylor Glacier blue ice area in Antarctica.Kr-81 sampling locations are indicated as blue dots.
Fourth, it does not require a continuous or undisturbed ice stratigraphy.
Of particular interest is the middle Pleistocene transition (1200–800 ka B. Such old ice can potentially be found in Antarctic BIAs such as the Allan Hills site (23), providing a strong impetus to developing reliable (absolute) dating tools for glacial ice.
Krypton is a noble gas present in the atmosphere at a mixing ratio of around 1 ppm (24) and has two long-lived radioisotopes of interest to earth sciences (25, 26): = 10.76 y).
Kr-85 is produced in nuclear fission and released into the atmosphere primarily by nuclear fuel reprocessing plants.
Kr-81 is naturally produced in the upper atmosphere by cosmic ray interactions with the stable isotopes of Kr, primarily through spallation and thermal neutron capture (27).