Earth’s ice cores preserve climate history of million of years. Most of the ice cores are taken from the ice deposited in Antarctica and Greenland. Some interesting facts…
Ice cores have been preserved in US National Ice Core Library (NICL) in Denver Colorado.
- Oldest ice core record kept there is 420000 years old.
- There are ice cores which have been collected and preserved from a single hole 3.6 kilometres.
- Total length of all the ice core samples preserved in the NICL is 20 kilometres.
How do these ice cores help in delineating the climate at that period of time. Dust and chemicals trapped inside the ice samples. Analysis of these chemicals and dust particles can delineate the climatic conditions prevalent in the different times in the past. Climatic histories upto 850000 years have been recreated.
How the age is determined??
Water like any other chemical contains normal oxygen 16 (16O) atoms as well as a very small fraction of oxygen 18 (18O) atoms. Water evaporation is a function of temperature. At higher temperatures 18O water evaporates more along with 16O water which means when these vapors condense will be richer in 18O. From the ratios of amounts of 18O and 16O temperature can be deduced.
Similarly trapped CO2 inside the cores gives the CO2 levels at different times in the past.