I agree that the paper is fatally flawed, but too many people misunderstand what ice core proxies are actually measuring. The isotope ratios used to reconstruct temperature are governed by processes over the tropical, subtropical, and extratropical oceans, not over the Arctic. The heavier O^3 isotopes are mostly rained out by 50-60N, in fact.
The isotope ratios within ice cores are, for all intents and purposes, hemispheric SST proxies. The Arctic cores depict SSTs over the Northern Hemisphere, while the Antarctic cores depict SSTs over the Southern Hemisphere.