If this is a new concept for you, here is a PBS episode that chronicles the scientist who developed this fairly new discipline of science (paleoclimatology): Lonnie Thompson. You can watch the entire episode for free online on the NOVA Science Now web site.
Although this episode doesn't discuss Noah's flood, it does explain how ice cores can be used as an accurate dating technique. It also mentions that scientists currently have ice core samples dating back to 750,000 years ago. In my opinion, this provides a rather compelling, and easy to understand, evidence against the young-earth creation model.
For more about Noah's flood and ice cores, in particular, see:
Seely, Paul H., "The GISP2 Ice Core: Ultimate Proof that Noah's Flood Was Not Global," PSCF 55.4:252-260. (12/2003) - Note: I personally disagree with Mr. Seely on a number of other points related to Genesis, but on this particular issue, I agree with him. For whatever that's worth...This might make an interesting exercise in critical thinking for students: How can ice cores provide insight into the age of the Earth? What does the Bible say about the age of the Earth?