Well hello there, Mark Serreze again. Today's lesson is on temperature, temperatures across the Arctic region. What I'm talking about in temperatures primarily in this video is the temperatures that we've measured about that high, that high above the surface. It's what we measure all over the world, it's what we call a surface air temperature or an ear surface temperature. Surface air temperature certainly a bit of a misnomer, but it's the term that we tend to use in the meteorological world. But temperature about that high in the surface, and that's what we really measure throughout the world and what we really feel and experience as humans. Key points about Arctic temperatures. First of all, huge spatial variations across the Arctic in temperatures and that holds as much for winter as it does in summer. But the patterns are very different between the seasons. Also, while we're primarily talking about this surface air temperature, I want to measure temperature inversions. That is, cases where temperature actually increases with elevation above the surface. Rather than the usual case where temperatures decrease above the height, above the surface. And why they are important in trapping pollutants, for example. Another point I want to get across is that the Arctic is warming faster than the rest of the planet, much faster than the rest of the planet. And that strong warming that we're seeing in the Arctic is punctuated by some amazing heat waves that we've seen in recent years. Now, let's first talk about spatial and temporal patterns of Arctic temperature. Think about the winter pattern first. What's going on in the winter, of course, is not much. Solar radiation are very little in the Arctic in winter, none at all, of course, at the North Pole. Where the temperature is lowest, where is it coldest? It's coldest, as it turns out, over the Arctic Ocean, Siberia, and Canada. But it's much, much, much warmer over the Atlantic side of the Arctic. Now that contrast very sharply with what we see in summer where it's the warmest conditions, highest temperatures are over land areas. Well, temperatures over the Arctic Ocean, ice-covered Arctic Ocean are pegged very close to 0 degrees C or 32 degrees Fahrenheit, so it's a much different situation. Now, this figure is showing average temperatures during the month of January. And the point here is that the ones in the blues, the areas in the blues are coldest, minus 30, minus 35 degrees C on average. And the red ones are where it's warmer, so the blues is cold, the red warm. Well, where is cold, where is it coldest? Arctic Ocean, Canada, Siberia, that's where it's cold. And I'm trying to show that with this blue arrow coming in, those blue areas, that's where it's really cold. Whereas if you look to the much warmer conditions, we find them over the North and North Atlantic. We have areas in the North and North Atlantic, well north of the Arctic Circle. Where January temperatures are barely below the freezing point or don't even get below the freezing point on average. It's really a remarkable contrast between this North Atlantic region to what we see over the Arctic Ocean, which is of course ice covered, and over the land areas like Siberia or northern Canada. Now, let's ask ourselves a question. Why are winter air temperatures so much higher over the Arctic's Atlantic sector than in these other areas? Well, I hope you didn't answer large undersea volcanoes because that certainly nodded. I'm not aware if there's any large undersea volcanoes in the Arctic. The real answer here is warm ocean currents and no see ice. What happens here is there is something called the North Atlantic drift. Some people think of it as the northern extension of the Gulf stream, it's technically not really right, but you can think of it that way. It's basically a warm ocean current that extends well into the polar regions in the Arctic on the Atlantic side. And what does that do? It's warm ocean and it keeps the ice from forming. This is a very important thing, if we look at the Arctic Ocean, we say it's quite cold in January. If we were to put a crack in that ice, open it up somehow, we would have a situation where a lot of ocean heat could escape to the atmosphere and make it much warmer. What the sea ice does is it acts as a lid and it basically separates a much warmer ocean from what is a much colder atmosphere. It acts as a lid, keeps the heat transport from going from the ocean into the atmosphere. Well, in the Atlantic sector of the Arctic, you don't have that. You have a fairly warm ocean water exposed right to the overlying atmosphere, and it's quite warm. And so as a result of, you have much higher air temperatures over that Atlantic side of the Arctic than you do over the Arctic Ocean or over these land areas. Now, this figure is showing the situation that we have in July, okay? That's basically Midsummer, July, the average temperatures. Again, the blues are where it's cold and the red toward warm, but what a different pattern we have. If we look over the Arctic Ocean, a lot of it is in that light blue color, and that light blue color is basically 0 degrees C or 32 Fahrenheit. Whereas over land areas in the Arctic, some areas could get quite, quite warm in terms of their July. Day, things like that, it's rather remarkable that it can get that warm in some parts of the Arctic over land. Now, why it's so warm over land? Well, we have a snow-free land area, it absorbs the Sun's energies very strong because it has what we call a low albedo, generally a little low reflectivity. Absorbs the Sun's rays readily, and some of that heat is then transferred up into the atmosphere. Well, what's happening over the Arctic Ocean is a very, very different thing. And we can ask ourselves a question then, why do summer air temperatures at the North Pole hover right around 0 degrees Celsius or 32 Fahrenheit? The answer here is simply that sea ice is melting. If ice is melting, its temperature right at that ice surface is right at the freezing point. That means the air above it, say that high above you, is just never going to get very far above freeze, it's going to hover right around 0 degrees C. So you can pour all kinds of solar energy into the sea ice. But instead of warming the surface and warming the atmosphere, it's just melting more ice. And the melting temperature of that ice is right around 0 degrees C. Hence so is the air temperature pretty much about that high above the surface, a very, very, very different situation. I mentioned temperature inversions. These are situations where temperature increases with height rather than decreases with height. The normal situation that we experience in most of the time is that temperatures decrease with height. And inversion as a different thing, temperatures increase with height. Well, he important thing is is temperature inversions tend to inhibit mixing. If you think about oil and if you try to make your own oil and vinegar, right, and you put them in a jar and they'll separate. And that's because these fluids have different densities. And the light fluid, which would be, I believe, the oil, stays at the top and the vinegar stays at the bottom. You could shake it up and it would still separate again, unless you really, really shook it for a long time. Same idea holds for a temperature inversion. And you can think of a temperature inversion as a situation where you have fairly light air that is low density air over denser air near the surface. And that inhibits mixing, and that's what happens in a temperature inversion pattern. And the importance of inhibiting mixing is it means that in parts of the Arctic, like industrialized parts of the Arctic, or even places like Fairbanks, for example, air quality in winter can be very, very poor. We think of the Arctic is so pristine, well no, it's got his air pollution problems in some areas, especially in winter, and a lot of that relates to a temperature inversions. This figure is showing what we call atmospheric soundings. These are based from these are done all over the world. But what I'm showing here is temperatures from some of these ascends for a series of stations in the Arctic. The x-axis from left to right, that's temperature, and on the y-axis is elevation above the surface. So if you look at those profiles, at the surface it's cold, but then as you move up to, say, one, or even two kilometres, temperatures increase with height. Then they start to decrease with height above that. That area from the surface upwards to maybe one or two kilometers where temperature increases with height. That is your Arctic temperature inversion, and these are basically ubiquitous in the winter. I mean, it's hard not to have one in the Arctic during the winter. You still have them in summer, they tend to be weaker, not as well-developed. But very much, they're very characteristic of the Arctic in the winter. And as I mentioned, these inversions inhibit mixing. This is a photograph from Eureka. Eureka is a scientific base, an Royal Air Force Base, and this is just showing the effects of an inversion. What it showing is the plume of condensate, mostly water vapor, that condensed into a cloud from the power plant there. And you can see that tries to rise, but it can't because of the inversion it just Downstream, when was this photograph taken? I'm guessing it might around, April, sometimes son still below the horizon. Arctic amplification. Remember I mentioned this. This is this observation, that the Arctic is warming stronger than the rest of the planet. Basically like twice as warm, as the rest of the planet, though the rest of the planet as a whole. Why? There's a number of reasons for this. We say that okay, it's warming, so because of that we are losing sea ice. But there's a climate feedback here, because as we lose the ice, that also makes the Arctic warmer. Issue here, is we warm things up, we started to melt some of that highly reflective snow and ice and also hold over land, over snow cover. We melt some of that and we exposed the darker underlying surface. Those really absorb the suns energy and result in even more melt and even further warming. So the warming is amplified in the Arctic, in part through what we call this feedback in albedo, feedback. Albedo, just being a fancy word for the reflectivity of the surface, but there's other things going on as well. Changes in cloud cover. Changes in the circulation of the of the atmosphere. There's a number of factors at work here actually, and the truth is, we do not have them all sorted out yet. There's a number of contributions, but yet there's still things we don't know. That Arctic amplification is absolutely here, and I'm showing this by this figure which is showing, the change in temperatures across the globe from 1961 through 2018. What we find is that most areas are warming, that is there in those warm colors. The yellows, and the oranges, and the reds. Little warning, some areas aren't warming yet like down in the down on the far South, down towards Antarctica. The some regions that actually happened warm yet, but most places have. But if you look with a real warming is occurring, those real bright red, turn your eyes to the North. That is Arctic amplification, it's having a big impact on the Arctic. Big impacts on ecosystems. We've also seen along with this overall Arctic amplification, Arctic heat waves. A great example was December 30th back in 2015, when temperatures at the North Pole got to the melting point. That is unheard of. I've been looking at Arctic temperatures for years and years and years, and I've never seen anything like that. It was caused by an unusual large transport of heat from the cell, warm air from the South. So it was certainly a weather related event, brought this weather system brought in a lot of warm air into the Arctic. So it's definitely weather, but I've just never seen anything like it. This is just showing the pattern of Arctic temperature anomalies, for that time. Anomalies is just were saying is temperatures with respect or compared to some long term average. And basically, the positive anomalies that is where is much warmer than average, are in those reds and you can see those bright reds there. Just amazing, temperatures at the North Pole, right around the New Year, December 30th, getting too the melting point, I've never seen anything like it. Thank you very much. [ BLANK_AUDIO]
