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I've been looking at reconstructions of the extent of ice at the last glacial maximum, while each map differs slightly (two shown below), most show a massive North American ice sheet, extending as far south as present-day New York. In western and central Europe, the ice sheets don't extend quite as far south. This isn't surprising, as western Europe is generally warmer than North America on the same latitude - a fact that is typically attributed to the action of the Gulf Stream. What's really perplexing is Siberia and the rest of east Eurasia. These areas seem to have virtually no ice sheets, despite being much further north than comparable areas in North America or Eurasia. Additionally, they're far enough east that I can't imagine they'd be strongly affected by the gulf stream. What would explain the differences?

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To add more detail to @Andy M's answer and your subsequent question in the comment:

Canada is much closer to the wet USA and there is no ocean in between. Ice doesn't have to correlate with the precipitation. Areas where there is precipitation will form the ice. When it gets thick enough the ice will flow under its own weight outwards from the centre, perhaps a long distance (this is the definition of a ice sheet/ice cap). A deep sea will interrupt the process as floating ice shelves act differently to land-supported ice.

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  • $\begingroup$ Thanks for the answer, this was insightful! You've said both that ice doesn't correlate with precipitation and that areas with rainfall are the ones that form the ice. This is a bit confusing, could you clarify? Additionally, you're correct that the USA is wet during this time (especially the great planes and NE). However, it seems (from @Andy M's map) that there is a similarly large, wet area in east asia at the same latitude - namely present-day Manchuria and even extending into Mongolia. I hate to ask - but could you clarify further? $\endgroup$
    – user2944352
    Feb 7 at 19:40
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    $\begingroup$ The first question I can answer quickly: areas with solid precipitation correlate with the 'accumulation zone' of the ice sheet. i.e. where the ice is forming and getting thicker. This ice can then flow/deform under its own weight/force to areas that don't have enough precipitation to form ice. Eventually it will reach an area where it is melting or 'calving' into the sea, the 'ablation zone' . When the rate of ice loss equals the rate of ice gain the ice sheet then and only then remain a constant size. This is called bring in 'mass balance'. You should be able to Google the terms in 'quotes' $\endgroup$
    – Mehmet Karatay
    Feb 7 at 21:29
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    $\begingroup$ I'll have to look at second part of your question when I have more than just a phone with me, as I can't just answer without looking things up. $\endgroup$
    – Mehmet Karatay
    Feb 7 at 21:30
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For ice sheet formation you need both cold conditions and precipitation, if it's cold but dry you will get permafrost, but not enough snow to build up glaciers.

This map of precipitation during the last age suggests eastern Eurasia was particularly dry in the north:

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Source: Wikimedia.org

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    $\begingroup$ Thanks for the answer, but based on your map it seems like Canada was similarly dry during this time period - yet had a huge ice sheet; this seems to suggest another factor might be at play. $\endgroup$
    – user2944352
    Sep 1, 2022 at 11:10

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