If you look at this map there was an ice bridge from Europe to North America and also the sea level being 300 feet lower would make both the Black Sea and the Caspian Sea just tiny inland lakes. Black Sea would be cut off from the Mediterranean Sea. So I can see the Aryans Hg R1a and R1b both crossing these two "seas" along the shore lines as well as maybe dwelling in them as people in those days lived near water sources for themselves and their animals. The Persian Gulf was probably a site of habitation as it is shallow and got filled in with the Ice Age melting. I think Central Asia was more grassy as the summer ice melt would have bloomed and animals would have migrated in summer towards it. In winter the grazing animals would have gone to the slopes of the Himalayan Mountains.
The Amerindians would have Hg R1a and X along with Hg Q and MtDNA A, B, C, D. Ii would make sense if they lived in the Arctic as the region is survivable. From there they could have migrated to North America. Soft snow would be the upper most cover then compacted ice below. Look at any any glacier and it is just accumulated snowfall built up over many, many years.
The Altai mountains show a grassy region My personal feeling is that R1a and R1b, and Middle Eastern people have a pronounced nose is because of the diet from goat or cow's milk. Goat milk has a higher Calcium content so those who have goat milk in their culture would have large noses e.g. Arabs, Jews, French, Southern Europe, etc. Hg R split from Hg P when they domesticated the goat. So this brings in the question of the date of domestication of goats which could point to the Ice Age.