Polar Bear Blog – Polar Bears in a Warming Climate

Well, there is a fair bit of chit-chat about the new IPCC report on Climate Change and the 15-year ‘lag’ in the warming trend predicted by computer models. This is not really a shock to anyone in Churchill – especially with a few years of ‘almost’ early freezeups.

For the record, I actually believe that humans, and specifically greenhouse gases, have altered the atmosphere. I find it a shame that both sides are so polarized and that just the basic common sense of reducing our impact and developing alternate energy sources seems like such an enormous task. We have made some strides but, at the same time, our thirst to develop the ‘emerging markets’ in China, Brazil and India far outweigh the meager steps taken so far.

So that’s a downer but I have some good news for polar bears. The language has changed in these statements from a few years ago. We used to talk about the warmest period in human existence and now, I hear the warmest time in 800 years instead. Nice to see that there is actual recognition that the Medieval Warming Period (950 AD – 1250 AD) was likely warmer than present-day… of course, this all still depends on which model you want to believe.

So, here is the good news for Churchill’s polar bears… 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. During their brief history in the area (7000 years or maybe even less), there have been two very significant warm periods – whether the actual populations survived these or migrated only to return when the climate cooled once again, its pretty hard to say.

The Laurentide ice sheet, which centred over Hudson Bay, peaked around 18-20,000 years ago. The dome centre over present-day Hudson Bay, reaching 5km thickness. The Laurentide began its retreat 10,000 years ago.

About 8000 years ago, it split in two over Hudson Bay, basically opening an opportunity for polar bears to move south (possibly) and exploit this new ecosystem. A thousand years later, this melt had created the Tyrrell Sea, a body of water that extended far inland of Hudson Bay. It would take another 500 years for the glacial ice to fully disappear, remnants linger on Baffin Island however. As the land rebounded, the Tyrrell Sea shrank and eventually became present-day Hudson Bay.

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.

The next warming period that I will talk about occurs around 950 AD. For about 300 years, the arctic seems to have been warm enough for extended ocean travel and human habitation. This is the time when the Inuit culture established in the arctic and Viking traders visited, at the very least, the eastern portions. It just seems common sense that there would have been less ice for these two maritime cultures to really expand their ranges.

So, these are two periods where there was likely less ice than today. 10,000 years is really a blip in evolutionary history for a species and during this time, polar bears have survived two major warming trends.  Then again, maybe Churchill’s polar bears did drastically decline in these warming periods… only to recover and repopulate Hudson Bay in the last 800 years.

Just some observations from a non-scientific background, but, to me, this seems like pretty good news… especially when you combine the fact that our present-day morbidity about polar bears stems from computer model calculations that now appear to be wrong. Doesn’t mean we can stop recycling and start building pipelines, though… just maybe that we can hold off on saving bears for a bit.

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