[SOUND] [MUSIC] Is permafrost, A permanently frozen water, B permanently frozen soil, C permanently frozen sediment, D Permanently frozen rock, E all of the above, or, F none of the above? The answer is E. Permafrost is any ground material that has remained below zero degrees Celsius for more than two consecutive years. >> This section deals with snow, a fundamental characteristic of the Arctic. It can cover landscapes for more than half the year, and even when the snow is gone during the summer, it can control processes that we see then, too. It directly affects people by providing water resources in summer, but it can also affect people negatively causing floods. So it provides opportunities and challenges. Some of these opportunities may be recreation, but then again there can be hazards through avalanches and the effects of a lot of snow on infrastructure. As well as the direct effects on people, snow also affects people indirectly. And this is mainly through the energy exchange between the Earth's surface and the atmosphere. And the most important perhaps component of this is the albedo effect, where snow reflects radiation back into space and thereby cools planet Earth. If we turn now to the animals and plants, then again snow provides both challenges and opportunities. For plants and animals, it insulates them during winter. It isolates the animals from their predators above that can't see them. But on the other hand, it limits the length of the growing season for the plants to grow and provide food for the animals that eat the plants. It also provides challenges when it thaws in the middle of winter and produces ice layers in the snow. In addition to insulating the habitat for some animals and plants during winter, snow insulates permafrost. And it insulates permafrost from the low winter temperatures, so permafrost thaws more easily, or faster, if there is a deep snow cover above it. Snow is a fundamental characteristic to the indigenous peoples in particular, who have had to work with snow conditions for more than half a year, every year for thousands of years. This has had an impact on their vocabulary which is very slanted towards the importance of snow for their day to day activities. So a lot of their words for snow depend on how they have to manage reindeer herd, or how the snow conditions affect their management of the reindeer herds. And also how it affects the access of the reindeer to food, the mobility for reindeer moving around, and also the condition of plants under the snow cover. However, the snow conditions are changing. As the climate warms, it has an impact on snow cover. And we are now seeing a record decrease in snow cover extent. And the graphic to the left here shows snow cover extent in June, a period at which snow is beginning to disappear as we move into summer. And what we see is less and less snow as we go through North America and Eurasia over the past 40 years. That means that the snow free period has increased, and that's increased by about two weeks over the last 40 years. But if we ask the question of when is it increased, autumn or spring, then autumn hasn't changed very much. But if we look at the other very colorful graphic, what we see is that spring has become earlier and earlier and earlier. And the deep colors show how much earlier the spring snow has gone over the last 40 years. Why? Why is the snow cover responding in spring and not in autumn? Well, we come back to this important word albedo. If we look at the earth's surface in the north, then snow and ice reflect a lot of the radiation falling on it, about 85 to 95%. As soon as we have tundra vegetation, this sort of plant you see here just growing slightly above the snow cover, that reduces albedo. But when we get the forest moving in, here's one example of Birch Forest in Lapland, then the albedo is greatly reduced, and heat is absorbed. By the time we have black spruce, the tiger, the coniferous forest moving in, only 5% of radiation is bounced back into space. So when the sun is up in spring, the reduced snow cover through climate warming results in increased warming that further increases earlier snow melts. This is a positive feedback loop. Climate warming, less snow, more heat absorbed, greater warming going round and round in a circle, a reinforcing circle. However, it's more complicated than that, because there is what we call a double-whammy for snow due to the impurities in snow. And these impurities are both natural and manmade. If we look Svalbard in the high Arctic, the photograph to the left here shows an international settlement that knew all the southern Svalbard on a typical clear day. The other photo shows what it's looking like more often. This is called Arctic Haze. And indigenous peoples of the Arctic have been reporting this throughout the Arctic now for many years. What's happening? Well, this is what's happening. Particulate black carbon, soot, is being released from rather dirty industries in industrial countries further south. And this has been transported in the higher atmosphere, and you just see this wave touching now Svalbard where the photograph was taken. Even at this side it's actually hitting northeast Greenland, a very remote Arctic area. But all that black carbon is landing on the snow, and it affects or reduces the albedo of the snow. If you look now, at the graphic with the little round dishes, these dishes are divided into half. And there's a clear filter, and there's a filter from the snow which is dark. And that darkness shows the extent of the change in albedo through the particles of soot that have landed in that area. And you can see some very dark patches that's quite impressive and worrying. Those were manmade effects in albedo. But also microorganisms grow in snow and in the melt pools on top of snow, and they have various colors. And these colors also effect albedo. In the graphic to the right, you see different species or microorganisms that inhabit snow and glaciers either in Northern Sweden or in South-East Greenland in this case. But they're everywhere. And you see the very different effects they have on the snow surface. And these affect the albedo of the snow surface. And scientists are now calculating how much these affect the albedo. And snow is becoming unpredictable. We've seen the trends we can measure. But in addition to those trends, we have day to day events or trends that we don't understand so well. So snow cover is becoming unpredictable. We have increased mid-winter thaws. And you'll hear in detail about that later on and the effects they have on reindeer and musk ox and lemmings. But what I will deal with here is their effects or some of their effects on vegetation. The picture we see here is a forest, a pine forest, in northernmost Norway, Norwegian Lapland, on the coast. And if you look at the ground vegetation, it's more or less dead. It's brown. What happened? Well, it could be a fungal disease. It could be some natural damage. But in fact, we worked with reindeer herders and we understood that this could be an event not when the photo was taken but in the winter before. And if we look at the winter before and we look at temperature, what we see in December is normal temperatures, -12, -10. But suddenly they go above 0. There is a thaw. And if you look at the bottom graph, you can see that the snow cover has gone. No snow in the middle of winter in the Arctic for a few days. But after those few days, then it gets cold again. You see the temperatures going down. The snow comes back, but the damage has already been done. And in this particular case, our satellite photos show us that this reduced productivity was 30% of plant growth, and covered 1,400 square kilometers. So what happens in just one or two days in the middle of winter could affect large areas for a long time. Snow also forms glaciers. But this is a topic for the next section. >> Which of the following is true? Is it A, snow cover is decreasing at the same rate in spring and autumn. B, snow cover is decreasing faster in spring. Or C, snow cover is decreasing faster in autumn.
