This is not climate related, as such, but a geological conumdrum – see www.sciencenews.org/view/generic/id/351788/description/News_in_Brief_Mil… … this happened in the Pliocene, which in geochronology directly precedes the Pleistocene and as a result of uniformitarianism is duly dated millions of years ago. The evidence of ice melt in Antarctica comes from sea floor sediments 300+km from the continent. The sediment core was rich in algae, a sign the ocean was warm. These sediments appear to have been washed into the sea from the Antarctic continent – which means that continent was itself warmer than now.
The same story is at http://phys.org/print293627243.html … where it is blamed on 'global warming' five million years ago – an idea that comes about as the Pliocene climate at the Poles was apparently somewhat different than it is today. Why is of course a matter of assumption – and in the uniformitarian model the only assumption can be global warming. Pole shift is out of the question, moving continents is disallowed, and so on. Interestingly, and just saying not advocating, in their book, When the Earth Nearly Died (Gaateway Books, Bath:1995), Allen and Delair (SIS has published several articles by them) claimed the Pleistocene was invented when the Ice Ages were added to an already existing geochronology – in the process moving the Pliocene back in geological time. In their model the Pliocene overlapped the Pleistocene – which would then imply a more recent ice melt than the author's of the above paper allow. It also affected Greenland, at the same point in time – are we talking about one of the interglacial periods, perhaps even the most recent one, the Eemian?