The latter. Anything under the glacier would be pulverised into dust (the glaciers even carve out their own valleys). These artefacts must have started up above the ice (on top or down a crack), so the people would have been hunting on the ice or maybe travelling across it.

Almost certainly icy areas, simply for the fact that the weight of the ice could easily crush and mangle any artefacts if the ice formed over them while they'd have much better survival chances the higher up in the ice layer they spent the bulk of their time in. Ötzi for example was travelling through a cold and icy region, it is what preserved him (although he's 3x as old).

Ice weighs 0.919 grams per cubic centimeter or 919 kilograms per cubic meter, for those of us more familiar with inches/feet that means a cubic foot of ice 57.4 pounds. That weight adds up quickly.