Siberia (Beringia) during last glacier period Today, Northern Russia is considered quite cold. It is not populated because it has low biological productivity: low light and cold. It can be below -50 at winter and 10 C at summer peak. It is low populated because there is basically nothing to eat. Poor reindeers dig some moss from below the snow, which grows there a little during short summer period. 

I am telling all of that, because I cannot even imagine what the hell Yakutiya would have been when all north of the continent was 1 km below the ice! Siberia stays permafrost even now, when you have warm summer days +5 Celsius. Certainly, it had to be frozen at glacier time permanently. Meantime, it is curious how people managed to cross the Bering Land Bridge during that latest glacier. How was that possible at that time, was it a Polar Voyage? 

Now, I read that Yakutiya was a wild life refugee during the last ice age. It had much more rich wild life than now, comparative to what we have in Africa today. People appeared there 12 000 years ago, when half of the Great Glacier was melted



and slaughtered mammoth. The mega-fauna extinction collapsed Siberian ecosystem, say scientists who undertake an attempt to recover it. They tell that mammoth grazed grass. Did they procure it from below the snow, like reindeer do? Ok, Beringia says that 


  During the ice ages, Beringia, like most of Siberia and all of north
  and northeast China, was not glaciated because snowfall was very
  light. It was a grassland steppe, including the land bridge, that
  stretched for hundreds of kilometres into the continents on either
  side.


Fine. But, the fact that all ice was concentrated over Europe and Canada does not mean that Beringia surface was not permanently frozen. If there is so cold that whole Europe is under 1 km of Ice, the cold Beringia must be frozen either, despite all ice is over Europe. We can have low temperatures without ice, right? And, if it was terribly cold in Europe, it must be at least that cold in Beringia, right? So, what could poor animals eat there, in the frozen desert?

To summarize, my question is: 

How is this nonsense possible that the 'freezer' of our planet was flourishing, whereas the rest of the Planet was starving in frozen state during last glacier period? 

PS! I was suggested to look at the climate zones during Last Glacier. I have seen it but I cannot believe that northern Canada and Greenland was thriving forest whereas almost whole US was under permanent ice sheet. Similarly, we see that Tundra (current Eastern Siberia state) ruled in permafrozen Beijing whereas Eastern Siberia was enjoing same thriving steppe Forest that Alaska did



That is unbelievable and that is what I basically ask to explain. I guess that I have just mismapped the colors. There are too few colors. On the other hand, if anomaly did exist, I want to hear that explicitly, desirably with explanation. Is it really large animals who maintained the warmth at the very north (see "Park" above) before people exterminated them or what?

PS2 I have revised the climate zones map and realized that we had Polar Desert in Siberia and Alaska rather than Forest Steppe. This makes more sense. But how did we had the large animals and thriving greenlands there anyway? Polar Desert is incompatible with green land, obviously. Polar Desert at zones map seems also to contradict the Beringia article, attributing Beringia to grassland steppe during Ice Age.
This paper basically summarizes the thinking behind the highly-productive mammoth step theory:

Zimov, S.A., Zimov, N.S., Tikhonov, A.N., Chapin, F.S., 2012. Mammoth steppe: a high-productivity phenomenon. Quaternary Science Reviews 57, 26–45. https://doi.org/10.1016/j.quascirev.2012.10.005

The idea is basically that a large herbivore density (comparable to modern day intact African Savannah ecosystems) kept soil moisture low and reduced permafrost temperatures. This was favoring gramminoids (grass like plants) that are much more productive than the present day prevailing mosses. Plant productivity in these regions is usually limited by nitrogen (other ecosystems are carbon limited). The higher than today herbivore population provided a lot of nitrogen input from dung and urine propelled the productivity of plants, which in turn allowed for more herbivores. Low temperatures and shorter summers also limited damage to gramminoids, thus they could grow faster in the next season. The ecosystem had several positive feedback mechanisms sustaining high productivity.

When humans arrived in the region, they hunted all the herbivores. The system collapsed and lost its productivity.