I've already researched a lot about the ice core records.
And I found It's dating is very much accurate.
There is no room for bias counting date because of several independent dating strategies.
You can synchronize it with volcanic ash layer. And the counting method is not only by visual layer but also by using "stable isotope data" at least 8,000 plus years records.
http://www.iceandclimate.nbi.ku.dk/research/strat_dating/annual_layer_count/ice_core_dating/
Young Earth Creationists claims are fraudulent.
For example, Larry Vardiman mention about "P-38 Lightning fighters trapped under an estimated 250 feet of ice for almost 50 years" below.
http://www.icr.org/article/ice-cores-age-earth/
But, Larry Vardiman did not mention about how much snow accumulate at crash site.
You can see where the crash site is from this video.
https://www.youtube.com/watch?v=n1I9C5lYaRs
There are much snow fall in south east coast area of greenland. And "250 feet of ice for almost 50 years" is quite normal and expected level for its crash site.
You can see how snow fall levels are different depend on the site.
http://nsidc.org/greenland-today/category/uncategorized/
If you must compare the crash site with icecore site. It must be DYE-3 Greenland or "Law Dome" Antarctica.
Young earth creationist like Larry Vardiman never present the real truth. But they present the deluded truth of the Bible.