Ice core shows its age
A second Antarctic sample excites climatologists.
Scientists have drilled right to the bottom of an Antarctic glacier, creating a hole that is three kilometres deep. The ice core that they extracted is shorter than that from a similar hole made in 2004, but oddly it seems to be just as old.
Continue reading the story here.
Comments
It might be of benefit to readers to mention how ice core samples are dated. Clearly, it isn't as simple as counting tree rings--particularly if a shorter sample can be dated to be the same age as a long sample.
Are core sample ages objective, or do scientists have to use ancient climate data from other sources to decipher ice history?
Posted by: Daniel James Devine | January 24, 2006 02:14 AM
You're right, how they date ice cores is useful info: there's a nice summary here: http://www.ace.mmu.ac.uk/Resources/gcc/3-3-2-3.html
But essentially, its done by measuring how much time a variety of radioactive isotopes have had to decay, and finding 'anchor points' in the time line such as dust and gasses from volcanic eruptions which can themseleves be accurately dated from sediments cores from the bottom of the ocean. And at the top of the core, you can even see each year as an individual layer.
Posted by: Mark Peplow | January 24, 2006 11:32 AM