Bummer for caribou: Carbon dioxide is allegedly making the Arctic snowier and icier (except it's allegedly less icy in places where ice is desirable)

A Troubling Decline in the Caribou Herds of the Arctic by Ed Struzik: Yale Environment 360

Peary caribou have been particularly hard hit by weather-related events. Back in 1961, when the first aerial survey of the Arctic islands was done, biologists estimated Peary caribou numbers to be 24,000. Since then, at least two catastrophic freeze-ups that were caused by early fall ice storms and rains and early, short-lived spring thaws resulted in more than 90 percent of the animals starving to death because they could not punch through the ice to get to food. Peary caribou populations have fallen today to about 2,000 animals. Scientists in the far-northern Norwegian archipelago of Svalbard told me earlier this spring that they are seeing the same kind of icing take a toll on reindeer in that region.

While there is evidence to suggest that these severe icings have happened in the past, there are also signs that they are likely to occur more often in the future. In recent decades, the Arctic has been heating up twice as fast as the rest of the northern hemisphere — with temperatures routinely rising by 4 to 5 degrees F — making fall rains, early thaws, and severe icing events increasingly common.

Both caribou and reindeer are better adapted to cold than they are to warmer, moister weather. In cold, dry winters there is less snow to slow them down and sap their energy while they’re on the move or being chased by wolves. Less snow, especially if it is not icy and hard-packed, also makes it easier for them to dig down to the vegetation they need in order to get them through to the summer months.
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Komi reindeer herders along the Kola Peninsula in Arctic Russia are already complaining that their animals are losing 20 percent of their weight by the time they take them to slaughter. Not only is heavy snow making it more difficult to move the animals, warmer temperatures are delaying the winter round-up by up to two months because the lakes the herders need to cross are not freezing over as fast as they once did.