HOST: Hi, everyone and welcome. People are still trickling in, so we're just going to give it another minute or two. But thank you for joining us today and we'll get started shortly. 

OK. Well, let's get started. Welcome everyone to today's seminar by Jim Overland. Jim is a Research Oceanographer at NOAA's Pacific Marine Environmental Lab studying changes in the Arctic for over 40 years. Thank you for being here, and if you have questions throughout today's presentation you are welcome to enter them into the questions chat. We'll be monitoring that and get to the Q&A part after the presentation. Thank you. And, Jim, I'm going to turn it over to you. I think you just have to unmute yourself and we're good to go. 

JIM OVERLAND: [INAUDIBLE] 

HOST: There you go. Perfect. OK, we're good. 

JIM OVERLAND: Great. Good morning or evening everyone. As the case may be, in the last couple of years we're seeing more rare events in the Arctic of different types and I'm thinking this is a better indicator of rapid Arctic change than just looking at trends of individual variables. We're seeing things like in the pictures the sinkhole due to thaw of permafrost, wildfires, ecological impacts. The picture on the right are walruses that have come ashore because they've lost their sea ice habitat. 

There is a major philosophical issue with this on how we interpret an event that we've never seen before. Statistically you might think, well, there's a distribution of events and we're just seeing an outlier, but if you have additional information like there is global warming going on or that we may have interaction between different parts of the Arctic system. That this is all new information and there is some uncertainty then that you cannot really extrapolate from previous events even though we think that their frequency is increasing. 

Next slide. Here is my conceptual image of what's going on that a major forcer here is climate change, global warming, increase of CO2. This is impacting Arctic amplification which has increased temperatures and loss of sea ice on an ongoing basis. At the same time, we have very large natural variability in atmospheric circulation, storms, and polar vortex, and so on. And so it's the combination of this steady Arctic amplification and the distribution, I mean, extreme distribution of natural variability in the atmosphere. Both of those come together to create these new extremes that we're seeing in the last couple years. And I'll give several examples here. 

When we have new extremes in a physical system, how they impact downstream on humans and ecosystem depends on the life history of the animals and which part of that life history overlaps with the new extreme. Next slide So an example here of the large variability in the atmosphere you have the polar vortex in the stratosphere and the jet stream and the troposphere. Often they are locked in together. And you can either have a more elliptical powering. The light, white line shows the location of the strong winds in the jet stream. And on the left the cold air is pretty much locked into the central Arctic. 

But either on multi-week basis or for seasonals, you can have this more wavy jet stream pattern on the right where the jet stream is bringing more warm air from the South into the Arctic as you can see over Alaska. And downstream you have the winds out of the North bringing cold air down into the mid-latitude. And the Central and Eastern US is a prime candidate for that as well as Eastern Asia. 

Next slide. So here's an example of the type of new extremes that we're seeing based upon this interaction between sea ice and the winds. We've had a couple of winter examples where we've actually had a melting temperatures at the North Pole. And the ongoing lack of sea ice is allowing storms to propagate further North. If you have sea ice on the ocean surface that cuts off the fuel for the storms but with more open water the storm can go further North. As they move further North they bring more heat and moisture further North which melts the sea ice and so you have a positive feedback and create these types of new events in the central Arctic from the interaction of storms and sea ice loss. 

Next slide. So the way I'm thinking about it is you have external forcing from the global warming. Sea ice is part of that but then you have large random variations in the atmospheric circulation. And it's the combination of those two that create all these different types of impacts like Greenland, sea ice, mass loss, and wildfires, and lack of snow cover in the spring. And we've had occurrences of all these types of changes in the last couple years. 

Next slide. So a big one that PMEL has looked at is the lack of sea ice in the Bering Sea in 2018 and '19 that the graph of sea ice through winter and spring is shown on the left and the green and red line show that the lack of sea ice was really different than the climatology showing black. And this was due to one of those interactions that we've had thinning sea ice, and then the wavy jet stream showed up, as shown in the purple and blue in the upper right. And this drove warm air from the South over Alaska in the Bering Chukchi seas that kept the Bering Sea free of sea ice and thinning ice in the Chukchi Sea. 

And then as you see the wavy jet stream with a ton of cold air came down and reaches into the Eastern US. Bringing the warm air North over Alaska and additional heat to the atmosphere from open water helps the persistence of this pattern more in the last weeks in 2018 and '19 last eight months. The impact of the loss of sea ice goes through the whole food chain. 

Many species in the Arctic were-- like cold temperatures that were set up from the leftover from the ice ages and with the lack of sea ice and warm temperatures the preferred food for the cod and pollock fisheries of large zooplankton are replaced by smaller zooplankton. So they're not the typical fatty shrimp-like creatures that's the base of the food chain. 

At the top is the picture of lack of sea ice changes the habitat for ice seals and walrus and polar bears. Next slide. So the warm temperatures the pollock and cod fishery move further North in those two years. And a lot of people say, well, all the ecosystem will just move further North. But for the fishery in the Bering Sea, you have the warm temperatures coming in from the South that's not advantageous. But you still have ice in the North during winter. So the habitat for the fisheries will decrease in the future if we have more of these warm ice-free events. 

Next slide. One of the main ongoing Arctic changes is loss of the glaciers and ice sheets in Greenland. The loss over the last few decades is shown by the decrease in the green line on the left. But if you look closely-- and the dots are for every year-- if you look closely, though, some dots are closer together, and showing slower decrease or other-- and that's in the last decade. 

Prior to that, they were further apart with more rapid decrease. In 2019, you have a very rapid decrease. And what's going on here is, again, the interaction of the ice sheet with the atmosphere. If you have high pressure over Greenland, the wind flow is clockwise around that high pressure. And that brings southerly warm winds up along the west coast of Greenland. It increases the melt considerably. 

The dot graph on the right shows the correlation between having higher pressure than normal on the x-axis and the amount of ice loss on the y-axis. And the red dot shows that this is the main physics going on that led to the rapid increased loss in 2019. So again, when we have the random variation of the weather, that means that these changes are not always steady. That they're more of a pulse in different years. Next slide. 

We can also have the wavy jet stream increases, the severe weather. This Greenland the high pressure blocking area that's part of a four lobe wavy jet stream over the whole Arctic was in place before Hurricane Sandy. Normally with west to east flow of the jet stream, hurricanes that move up the East Coast are blown out to sea. 

But in the case of Sandy, with the Greenland high pressure blocking, the storm was steered on shore. And so you can have this interaction between the Arctic and the mid-latitude weather. The strong rains for the Houston hurricane was also a case where the jet stream was very slow. And there was enough time for a multiple day rainstorms that created their floods. Next slide. 

So we have the polar vortex connecting to the jet stream. And in winter, spring, 2020, for the whole time, the polar vortex, rather than centered over the North Pole, moved strongly to the Eurasian continent. And so this inset with the blue line is the jet stream being far south over Asia. And what's important about the polar vortex is it has some persistence of days to months. So the polar vortex helped keep this jet stream further south. 

And you're starting out with warm, dry conditions over Asia. And then that, combined with this southerly location for the jet stream, to maintain the conditions. And they had air temperatures of 100 degrees Fahrenheit, 38 degrees centigrade, that fed the wildfires and melting of permafrost. And when permafrost thaws, it's a one way street. Once that permafrost thaws, there is no way of going back to previous conditions. Next slide. 

Another example of the tie-in with the polar vortex is if the polar vortex is very weak, you can have high pressures in the jet stream location. And the picture on the right, the contours north of-- near the top, north of Scandinavia, those black lines are high pressure with the winds, again, clockwise. And when this high sets up coming out of the arctic, it pulls cold air down over the continents. 

And had the event they called the "Beast from the East", with heavy snow in England and reaching all the way down into Italy. So there's interactions example here as well. Next slide. 

So looking forward, these are the temperature projections from the latest sets of climate models. On the left, you have the annual temperatures on the global scale. In the middle, it's annual temperatures for the Arctic. And the Arctic is warming at least twice as fast as the globe. 

And the winter Arctic is increasing even faster. What I like to point out, in the different colors here are different scenarios in terms of CO2 mitigation. But what I like to point out here is up until almost mid-century, we're already locked in to increases of changes of 4 degrees in the Arctic. And so what happens in the second half of the century depends upon what we do now in terms of mitigation. 

On the right is the projection for loss of sea ice from the various models and scenarios. Keeping global warming to 1 1/2 degrees actually maintains the sea ice cover year-around. But the black line shows the reality here. That the real world is moving-- is losing sea ice faster than these climate models. And the reason for that is that the climate models are not very good at modeling the wavy jet stream and other interactive processes in the Arctic. Next slide. 

So coming back to summarize with my overview again. The ongoing steady Arctic amplification that relates to climate change interacts with interannual large variability in the atmospheric wind patterns. And the two of those create these new extremes. And that interact with the life history. 

And an example is from Ribbon seals north of Alaska. I think Ribbon seals are a nice art deco by whoever created them. But they need sea ice in May and June to molt and have their pups. And like most high latitude and sub-arctic species, they're actually attuned, due to the large natural variability in the climate, ecologically. 

And so they tend to depend on several strong year classes of new animals every decade. They don't depend upon a steady increase in their population every year. And so historically, these ice-dependent seals might-- there might be two warm years out of a decade that don't affect them very much, as there will be several other favorable years. 

But what is happening between these new weather extremes and their life history is that if we went up to, say, four or five really warm ice-free years in a decade, they'd start to be in real trouble. The ultimate impacts here depend upon how this variability plays out from year to year versus the life history. I also want to say a little bit more about these. 

Since we can't project from history on these events, other than we'll have more of them, but we don't know the exact type, location, and timing are less predictable or the-- one thing I can say that the-- I don't like to really say unpredictable or unknowable, because that has a bad connotation, I think, for a broader audience. 

But there is a way of thinking about the situation. Rather than thinking that we need to do extrapolations and come up with future probabilities. We can think more on developing a set of scenarios on what's possible. And then back figure from what kind of events we want to avoid and what kind of adaptation we have to have to take care of that. So thinking more in a scenario point of view than the probabilistic extrapolation. So that pretty much covers it. And willing to have some discussion and questions. 

HOST: Wonderful, Jim, thank you. If people have questions in the chat, please feel free to. I'm going to pull up some of the questions that have come in. Just one second. This is the first time we've had to [INAUDIBLE]. The first question is, the Pacific cod movement slide early in Jim's talk [INAUDIBLE] oh, was actually a talk from AMFS 2021. We'll get that updated in the slides. Then I think...Hold on, sorry, everyone. The chat feature is just a little more slow-going. So you can also raise your hand. 

So one question, Jim, is there a way to identify a trend in the rare events? Or is it too difficult given their stochastic nature? 

JIM OVERLAND: Well I think you could say that we're going to have more rare events. But you can't really nail down what year those might happen. In the Bering Sea, in 2020 and 2021, we've had more average ice conditions compared to that. And after 2018, I said, this is such a rare event, it will never happen again. And it happened the following year. 

So coming out with how to deal with that, some people call these new rare events extreme uncertainty. But again, I don't think that's a good phrase to use, because we do anticipate more of them in the future. It's just that you can't nail down what year they will be but certainly on a decade scale, we expect more. 

HOST: Thanks, Jim. Any other questions? OK, Jim. I'm going to mute you for a second while I read the question. And then just unmute yourself for the question. So we have another question that is about temperatures. Will a decreasing temperature gradient between the equator and the poles lead to slower evolution of the jet stream deformations. 

JIM OVERLAND: That's one of the strong arguments certainly, that makes physical sense. In the meteorological community, this is somewhat debated. And my issue on that is that's a truism if you think all the way around the globe. But these jet stream meanders are actually a tightening of the jet stream in certain locations. They're stronger in some locations and weaker in the others. 

So we've seen clear cases of the weather interaction between the Arctic and the mid-latitudes like that Bering Sea, Alaska, East Coast examples that the I showed. So we've seen that. But their forcing tends to be local, opening up the blocking high pressure over Alaska, over Greenland, and over the Bering Sea north of Europe. So I like to think in terms of these three blocking locations, rather than the average all the way around the globe. 

HOST: And then, there's a few more on temperatures. So I'll kind of just keep going on that trend. Also I see people have their hands raised or, well, they have-- I don't know-- you can use the hand raise feature, too. So the next question on temperatures was I understand why increasing global temperature result in a change. But I don't understand statistically why an increase in the mean would result in a change in distribution, i.e., longer tail of distribution to rare events. 

JIM OVERLAND: Sorry, longer what? 

HOST: Longer tail on that distribution. 

JIM OVERLAND: Well, it's because we're having the interaction with these storm events. Rather than just overall warming, that you have the storm events melting more ice, and creating more open water, or melting on Greenland. And the tails come from that interaction with the atmosphere circulation. 

HOST: Thanks, Jim. Let me-- hold on, working through. Just working, now, I'm just going to go back to the way they came in. But how would we speak to successfully-- how would we successfully speak to policymakers, who tend to focus on trends and means versus the sporadic nature of rare events?

JIM OVERLAND: That's a difficult but important issue. Rather than saying a large uncertainty on when these rare events will come, I think focusing on the impacts themselves, talking about storms or changes in shipping, or changes in the ecosystem are a better way of talking about. Rather than a few tenths of a degree warming trends. 

HOST: Then the next question is-- we got a comment and a question. Thank you very much for the great talk, Jim. I wonder if there's a strong indication of the atmosphere at land ocean coupled influences on the extremes, such as methane gassing. 

JIM OVERLAND: Absolutely. Methane and the change in permafrost when you have thawing, it's irreversible. But it also provides increased methane, which is a greenhouse gas. So again, it's one of these things where if you have a rare warm event, like the Siberian heat wave, that rare event speeds everything up. And it cuts in with all the different Arctic processes that contribute to the change. That's why I'm saying that these rare events are indicating that we're having faster changes in the Arctic than just temperature trends. 

HOST: Next question, forecasting in the Arctic generally suffers from sparse observations. If there was one thing you could get more of or more frequent that would help decrease this uncertainty, what would it be? 

JIM OVERLAND: We'd like-- we'd like weather balloons over the Arctic. But we're never going to get all of that. But maintaining the drifting buoys that can measure the increase in temperatures in the upper ocean is the doable thing with air droppable buoys that now can profile the ocean, rather than just give temperatures on the surface. I think that's really important. 

And models can help. But models need initial conditions and data to drive them. I'm concerned, with more traffic going through Bering Strait, that if we don't increase the number of ocean temperatures north of the Bering Strait, that we're for disaster on not being able to forecast some of the severe weather events. 

And without sea ice, there is more fetch for the waves. So even if you have the same types of storm systems, you can have more severe waves. And qualitatively, that if there's more open water, you would expect more energy going into the Arctic storms as well. 

HOST: Thanks, Jim. The questions just keep coming in. So we'll just keep going through them. Will global air pressure increase as global warming proceeds? 

JIM OVERLAND: Warmer-- warmer air is-- essentially creates increased distance between various pressure levels in the atmosphere. And so one of the issue of our mid-latitude reinforcing the wavy jet stream is more increased temperature, both from heat flux from the open water areas and warm temperatures coming in from the south increases the height of the pressure surfaces at the jet stream level. And that locks in the location. And since the open water areas don't move around, they tend to lock in the wavy jet stream in one configuration and increase the persistence. So the warmer temperatures more have to do with raising the high pressure surfaces and locking in a wavy jet stream. 

HOST: Next question is Mike Wallace and other climate scientists have pushed back against the polar vortex hypothesis advanced by Jennifer Francis and you, Jim. What's the latest on this scientific debate? Is there growing support and evidence for a weakening of the vortex due to diminished sea ice? 

JIM OVERLAND: This is an important question. And again, it's one of these that's hard for a general audience. The way that I look at it is from the picture I showed earlier, the polar vortex and the jet stream can go from the more zonal elliptical pattern to more of the wavy pattern. So if you have the elliptical patterning, the jet stream is well south of the sub-Arctic. And so there's not any chance for an interaction between the Arctic and mid-latitudes. 

You have to have a year or a month where, basically due to random variation, you can have the wavy jet stream. So I think Jennifer Francis is more stronger than I am. My view is the wavy jet stream, as I'm pointing out in this diagram here, the wavy jet stream is more of a random occurrence in how it starts. 

But once it starts, the more open water areas can combine-- can provide heating to the atmosphere and draw more heat from the south. So the change in the Arctic can help reinforce this wavy pattern. But it doesn't cause the wavy pattern. And that's how I straddle the middle ground between the skeptics and Jennifer Francis. 

HOST: There's more thank yous in the chat, too. And thank you for bringing your research to the discussion. They're wondering what spaceborne satellites you're using for your analysis. Wait, Jim, you have to unmute yourself. Jim, try one more time to unmute yourself. We were doing so well. 

[INTERPOSING VOICES] 

JIM OVERLAND: The satellites are where we get almost all our information here. And they've been around for over 10 years with major help in terms of where sea ice is. There are profilers that give temperature soundings that go into setting up where the jet stream and the wings are. And so the combination of the few land stations, and the satellites, and better quality models that are adding the satellite and land information. 

So I'm a major consumer. I don't particularly work on evaluating the satellites. But I'm really pleased what both the satellites and the improved models are doing, compared to where we even were 5 to 10 years ago. 

HOST: And it looks like the last few comments are-- one is great to see you continuing in this important work, Jim. It is especially interesting to see, again, that decisions we make today have life changing implications for the near future. Great talk. Thank you. And also one from AJ Resing, working with IABP via OPC and USNIC, which I don't know what the acronym stand for, but to supplement ice OBS with more marine OBS in open waters. And so your comments on profilers were taken to heart. So thank you. 

And with that, it looks like we have gone through all of the questions, unless there's a few last minute ones. And so if there aren't any more questions, we will conclude for today. And we will get this recording up on PMEL's YouTube channel as well. So thank you everyone for joining us. And Jim, thank you for the great talk. 

JIM OVERLAND: Thanks for the good questions. And yeah, there is hope. But things are moving faster than the climate models are saying for the Arctic. So we should be bringing that out. And was pointing out how we communicate the increase in extremes is an important issue. 

HOST: Great, thanks, Jim. And with that, we will-- everyone, I hope you have a great rest of your day. Thank you.