First off that article is not at all scientific, and his sources and explanations are questionable at best. As well as his motivations.
Here, I will give you a snipet from an actual scientific site.
http://chemistry.beloit.edu/Warming/icecore/ Ice Core Dating
By sampling at very fine intervals down the ice core, and provided that each annual layer of snow is thick enough, several samples from each year may be measured for the different chemical properties. It has already been seen that the delta value is related to air temperature when the snow was deposited. Because it is warmer in summer and cooler in winter, and provided the snow layers are not too disturbed by wind, the delta value can show annual cycles. Thus, these values can be used to date the ice core. Hydrogen peroxide is created in the atmosphere by a chemical reaction that requires ultraviolet light. There is a lot less ultraviolet light in the winter than in the summer in Antarctica. Thus, measurements of hydrogen peroxide dissolved in the ice also provide a good annual cycle indicator.
In order to date the ice cores accurately, the annual layers need to be thick enough to obtain about ten measurement samples from each year. The thickness of the annual layers depends on how much snow falls each year. Thus, to obtain an ice core from which accurate, detailed dating can be derived, we need to find an Antarctic site where the snow accumulation is relatively high. This would usually mean we need to find a low elevation site, but it must also be a site where there is no melt. If the snow was to melt at any time during the year, some measurements such as those involving trapped gases would be spoiled. In addition, the annual layers would be destroyed by the melt water which would, effectively, wash the evidence away.
Such locations (high snow accumulation, yet low summer temperatures) are not easy to find. One such location, however, is near the summit of Law Dome, approximately 120 kilometres from Casey Station, where an ice core has been drilled 1,200 metres through the ice sheet to the underlying bedrock. Accurate dating for this core has been obtained back to 8,000 years ago using annual cycles obtained by analysis of delta value and hydrogen peroxide. A section of the graph of delta value and hydrogen peroxide is shown in Figure 4, along with the year. The ice core depth for this section is 139 to 128 metres, corresponding to the dates 1807 to 1826 AD.
As you can see, scientists take this into consideration already, and make allowances for it, so to say that you Mr. Oard is wrong is an understatement. You need to be careful where you get your sources, if you are going to argue science, you should get your information from scientific sites.
Creationist websites as well as YEC sites etc have an agenda, they will do their best to prove their points, but they ignore evidence that will disprove their theories very quickly.
The evidence for this is easily found, if you are interested in looking.
Also, my post above was not complete, not by a long shot and I apologize.
Someone above said that the snowfall near the coast is much greater then within the mainland of Greenland, and this is indeed true, a major percentage of the ice over the planes is due to this, but, the other reason that it is so deep is the one that I explained above. The flowing of the pack itself has driven the planes deeper into the pack.
There, that is a bit better.
Such is the pitiable nature of "invincible ignorance".