The history of the world comes to life when scientists extract ice cores from the coldest places on the planet, like Greenland and Antarctica, to learn more about earth's climate way back when.
The hardened plains and peaks of ice that make up Greenland and the Antarctic preserve information about Earth’s former climates, going back millions of years. As snow accumulates in these regions year after year, the higher snow layers exert pressure on the lower ones, squeezing out air. Under pressure, snowflakes transform into dense grains of ice that fuse together into glacial sheets.
But not all the air escapes. About 10 percent of it gets trapped when snowflakes transform into ice crystals. Those miniscule air bubbles contain the atmospheric gases—nitrogen, oxygen, carbon dioxide, methane—from the time periods in which they were trapped. Climate researchers are particularly interested in the greenhouse gases.
“Ice cores are the primary way in which we reconstruct the atmosphere going back a million years or so,” says paleoclimatologist James White, professor at the University of Colorado, Boulder and director of the Institute of Arctic and Alpine Research. “It’s one of the few archives of the past that is clean enough that you can actually get carbon dioxide and methane concentrations.”
Read the rest of the Nautilus article Secrets in the Ice as the Polar Bears part will astound you. :)