Long-lasting ice-free arctic around 5-6k years ago?

Polar Bear Blog – Polar Bears in a Warming Climate

We talk about how polar bears are 200,000 years old as a species, etc, but Hudson Bay is one of the newest ranges in the polar bear world.
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In the following years, the climate drastically warmed. The climatic optimum for Hudson Bay is believed to have occurred between five and six thousand years ago. Of course, it is possible that the warm temperatures were moderated to some degree by the last remaining glaciers.

There is real evidence that the arctic was ice free in the summers, including landfast ice. The evidence cited is that driftwood was found high up on beach ridges on Ellesmere Island – driftwood cannot reach land if it is locked in with ice.

This warm period may have lasted for some time, there is evidence that 3500 years ago the treeline extended north to Dubawnt Lake, 280km north of its present location. To me, at least, it seems like the climate around Churchill (and much of the arctic) may have been at least as warm or warmer than present-day for at least 1000 years if not more.