I'm John Walsh, I'm a research professor at the University of Alaska in Fairbanks in the United States. I don't have a direct role in mosaic, but I've worked on many of the topics that mosaic is addressing, I've spent about 30 years looking at observational data for the Arctic, analyzing it and comparing it with climate models, and behind me is a scene of Fairbanks, Alaska in mid-December, about two days before the winter solstice, and that serves as a good setting for some of the changes will be talking about beginning with the first slide. So our first slide here shows the scene we just looked at in the introduction, but it shows the same area from about 20 years ago on a December day when there was ice fog present. Ice fog, it used to be fairly common in the Fairbanks area, it forms when the temperatures down around minus 40 degrees or colder, you might have noticed in our introductory shot that there was no ice fog, in fact there were clouds, and it was quite a bit warmer. That's one indication, that's the warming that we're going to be talking about has really set in, at least in Alaska and in the rest of the Arctic. There are two key messages that we'd like to get across as we go through this story of the Arctic warming and its impacts. The first is that climate change is apparent throughout the Arctic, and that means the air, the land, the ice, and the ocean, all parts of the Arctic system. The second main point is that these changes are already impacting the Arctic, it's impacting people, wildlife, and the environment. Here's the first summary of the warming. It's a graph of how the Arctic temperatures have varied year-by-year going back to 1880, and what stands out here is this cluster of warm years, the higher values in the last decade or two, we are warmer now than we've ever been in the last 130 years, and you'll also notice that not every year is warmer than the previous years, they're ups and downs along the way, but there's an unmistakable trend in the record. Here's how that trend maps out geographically. You'll notice here that the red colors, which indicate the highest warming, are centered over the Arctic Ocean, in fact, the mosaic ship is right in the middle of the red, where the warming has been between two and four degrees Celsius since about 1960, that pattern is called Arctic amplification, the Arctic is warming more rapidly than the rest of the world, so it's amplifying the global warming. There are impacts of that warming. So I'm going to start with the impact on sea ice. Sea ice is one of the main topics that mosaic is addressing. Here's a record of these September sea ice extent in the Arctic Ocean, and you'll notice a downward trend very consistent of the warming climate, in fact, the last several years have had the lowest extent that's ever been recorded in the Arctic Ocean, that's the ice extent in September and there are impacts of that. This figure here, which is from a climate impact assessment, the Arctic Climate Impact Assessment gets at one of the impacts, which is that uses of the ice have changed, ice has typically been used or historically been used for travel by coastal communities. This is a dog sled team that's trying to make its way over the new Arctic with its sea ice that is much thinner, much less stable than it used to be back in the 1980s and the 1990s, just one generation ago. Here's a record of sea ice in the Bering Sea, and that's the region to the west of Alaska, this is a region that gets it sea ice only in the winter time, and what stands out here is a remarkable drop in the ice extent in the bearing in the last few years, in particular, the last two winters, there's been very little sea ice in that region, it's another sign that there's something going on in the climate system and the Bering Sea is a striking example in the recent decades. There are impacts of that loss of ice, the ice serves as a protective buffer for the coastline, when storms come along, the ice cover can damp the waves and essentially prevent waves pounding against the coast, producing flooding and erosion. Here are a few scenes from Western Alaska during the last few winners. On the left, we have a couple of examples of flooding that has occurred in Alaska and coastal communities, these are during times when the sea ice was absent. Historically, it might have been present at that time of the year. On the right, we have examples of erosion. This is an area of the north coast of Alaska where you can see a large chunk of land that's been eroded away by the warmer water lapping up against the coastline. There are impacts on land as well. We have in this diagram a record of the number of days when smoke was reducing visibility in interior Alaska, this is actually based on the observations from the Fairbanks airport, a number of days when they've reported smoke has become higher over the past decade or two, the smoke events don't occur every year, but you can see from this diagram that they've become increasingly frequent in the last decade or two, so there's an impact on interior communities as well as coastal communities as the climate changes. Here's an example that represents an impact on wildlife. These rain on snow events, freezing rain events are becoming increasingly common in the Arctic in the wintertime, is the air temperature warms up above freezing during winter, snow cover is still present, that sets the stage for freezing rain or icing, and the icing can create layers that prevent grazing animals from reaching the food sources that they're used to during the winter. This is an example of a caribou herd, and there was an event a few years ago that led to the death of 60,000 reindeer in Northern Siberia, again, that's tied to this increasing frequency of freezing rain events, and the ground itself is warming. These graphics here show the temperatures measured in the ground in Permafrost in northern Alaska over the last three or four decades, and there's unmistakable increase here, the ground temperature, even down at the depth of 10 or 20 meters, has warmed by several degrees C, and you don't have to take that record too far into the future before you're approaching the freezing mark, which means that Permafrost will actually thaw and that has implications for the state of the ground, there can be settling of the ground as ice below the surface melts, it has implications for any infrastructure that's on the ground, roads, buildings, for example, are going to start to settle and become uninhabitable or unusable. Our last slide showing an impact here, is one that highlights the potential impacts of the Arctic warming on middle latitudes. The impact here is through the jet stream, the popular media sometimes refer to the jet stream as the polar vortex, but there are indications that the warming of the Arctic maybe altering the jet stream patterns, the warmer atmosphere at high latitudes changes the pressure gradient, which controls the jet stream, and there are some studies that have shown that the jet stream has become increasingly wavy, which leads to persistent warm or cold events in mid-latitudes, so this is an area of active research, but it is one where the impacts of Arctic warming would extend beyond the Arctic into mid-latitudes, and that would be an example of how what happens in the Arctic does not stay in the Arctic.
