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The Changing Arctic –Part 3

The weather page is prepared by Daniel Bezte. Dan has a BA Honours degree in geography, specializing in climatology, from the U of W. He has taught climate and weather classes at the U of W, and is a guest climate expert on CJOB’s morning show with Larry Updike. Daniel runs a computerized weather station on his 10 acres near Birds Hill Park, which he plans to develop into a small vegetable and fruit hobby farm.

Daniel welcomes questions and comments at [email protected]

Idebated whether I should continue our look at Arctic sea ice or interrupt our look at this to discuss last weekend’s unusual storm system, but since the storm was still playing out as I was writing this I decided to wait until it was finished before writing about it…so Arctic sea ice it is!

Last article, we finished by introducing the idea of a positive feedback loop. One of the reasons that the Arctic is so cold (besides low sun angle and little to no sunlight in the winter) is that a good portion of this region is covered in ice and snow. Both of these substances are highly reflective, or have what is known as a high albedo. Most of the sunlight that does make it to the surface gets reflected away (about 80 per cent) and does very little to help heat the area.

If we reduce the area of the Arctic that has a high albedo, then more of the sun’s energy will be absorbed, allowing the region to heat up more. The extra heat further reduces the area with high albedo, so even more of the sun’s energy is absorbed – a positive feedback cycle. One change feeds back on itself, creating a bigger change.

If the Arctic was only land area, I don’t think people would be getting as excited about what is going on. But the Arctic contains a lot of water, most of it in the form of the Arctic Ocean. What’s the big deal about all the water? Well, water can absorb a great deal of the sun’s energy (around 80 per cent). Water can also move that energy around. Finally, water can also store the sun’s energy (heat) for a much longer time than land. So, if the amount of sea ice drops, then a lot more energy, or heat, can be added to the Arctic, leading to our positive feedback cycle.

Now just how much sea ice is there in the Arctic and what is its current state? Before satellite records began, measurements of Arctic sea ice came in the form of reports from ships in the region, explorers and scientists, and the different indigenous groups living in the Arctic. While a lot of good information can be gathered from these reports we can’t really create a reliable record of monthly or even yearly sea ice amounts until the early 1970s. This is when NASA launched a microwave imaging satellite that passes over the Arctic several times a day collecting daily data on Arctic sea ice.

Then in 1978, NASA launched a new multi-channel microwave imaging satellite – this is seen as the beginning of really useful satellite data. This means that fairly reliable continuous records of Arctic sea ice only go back 31 years, not bad, but not great.

What patterns have we seen in the Arctic sea ice over this period? Well, unless you are a conspiracy theorist and believe that NASA and everyone else looking at this data is in on some massive coverup, it is pretty evident that the amount of sea ice in the Arctic is going down. I have included two graphs showing average monthly sea ice in March (month with maximum ice cover) and September (month with minimum ice cover).

From the graphs you can definitely see that while there is yearly variation in the amount of ice cover, the overall trend (depicted by the blue line) is a downward one.

Looking at the September minimum graph we can see that over the last 30 years, ice cover has dropped from around 7.5 million square kilometres to around 5.5 million. That is a change of about 2.0 million square kilometres or about a 30 per cent decline!

In our next article on Arctic sea ice we’ll explore the current ice conditions and what factors have possibly been influencing this rapid decline.

About the author

Co-operator contributor

Daniel Bezte

Daniel Bezte is a teacher by profession with a BA (Hon.) in geography, specializing in climatology, from the U of W. He operates a computerized weather station near Birds Hill Park.



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