A mom and two cubs venture out onto newly formed ice.

© Daniel J. Cox/Natural Exposures.com

12/7/2015 9:58:53 PM

Hudson Bay Ice

Note from PBI: Climate and sea ice specialist Kyle Armour wrote this blog post last month before sea ice had started freezing near Churchill, Manitoba.

Throughout November, sea ice extent was above average in eastern Hudson Bay, but below average in the western part of the bay. Looking at the entire Arctic, sea ice extent for November 2015 averaged 10.06 million square kilometers (3.88 million square miles), the sixth lowest November in the satellite record. This is 910,000 square kilometers (351,000 square miles) below the 1981 to 2010 average extent.

Currently, there is enough sea ice along the coast of western Hudson Bay to allow polar bears to venture out and begin hunting seals. Check out PBI's Bear Tracker to see where Western Hudson Bay polar bears are on the bay right now.

I'm extremely excited to be out on the tundra this year working with Polar Bears International to produce webcasts about polar bears and climate change. My role here has been to discuss topics related to my own research, such as how and why the Arctic sea ice cover has declined over the past few decades, and what the Arctic might look like in the future.

I'm a newcomer to this world of polar bears, but have been learning quickly. It's been an amazing experience seeing the bears here on the shores of western Hudson Bay. Our location is the prime spot for them to gather and wait for the sea ice to return.

On average, freeze up now occurs about two weeks later than it did in the 1980s. In fact, Hudson Bay's polar bears spend about a month longer on land now than they did just 30 years ago, due to the combination of these later freeze-up dates and a shift toward earlier seasonal sea ice breakup-both of which have been driven by rising global temperatures.

Yet, there is natural variability on top of these sea ice trends, which means that every year is different from the last. For instance, this summer's breakup of sea ice in Hudson Bay occurred a few weeks later than it has in recent years. The summer's extended seal-hunting season has led to some healthy-looking bears around here, and we've even seen a handful of moms with one or two cubs this week-everyone's favorites. These heartening sightings go to show just how important a few extra weeks on the sea ice can be for polar bears.

The question on every bear's mind is, when will Hudson Bay freeze up again? If it were a few decades ago, they'd be out testing the ice by now, instead of napping outside our Tundra Buggy®. From the buggy we can see some ice forming along the coast, yet satellite observations show that this band of sea ice doesn't extend very far-the open waters of Hudson Bay are almost entirely ice free right now. While air temperatures have been hovering a little below freezing for the last couple of weeks, and strong Arctic winds have been blowing, it simply takes a while for the deep waters of Hudson Bay to cool to the point where sea ice can form.

Looking at sea-surface temperatures gives some indication of whether this year's freeze up might occur sooner rather than later. While some regions of western Hudson Bay are warmer than average right now, much of the Bay is actually cooler than average-perhaps in part due to the late breakup of sea ice this summer. This suggests that the freeze-up has the potential to occur somewhat earlier than in recent years. But, importantly, whether the sea ice will grow quickly or slowly depends largely on the weather over the coming weeks, which is difficult to predict with any accuracy.

Only time will tell how long the polar bears here will have to wait to return to their home on the sea ice. For now, all we can say with confidence is that if global warming continues unabated, years like this, with healthy-looking moms and cubs, will become less and less common.

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