Eyes on Earth Episode 20 - Mapping Alaska's Permafrost

STEVE YOUNG:

Hello everyone. Welcome to this episode of Eyes on Earth. Our podcast focuses on our ever-changing planet, and on the people here at EROS and across the globe who use remote sensing to monitor and study the health of Earth. Iím your host, Steve Young.

Todayís guests are Bruce Wylie and Neal Pastick. Bruce is a U.S. Geological Survey scientist based at EROS who has traveled to Alaska annually for a decade to study the state of near-surface permafrost in that part of the world, and his collegue, Neal, a physical scientist with KBR and a contractor to the USGS, has participated with Bruce on that field work as well.

Alaskan permafrost contains vast amounts of carbon in organic matteróplants that took carbon dioxide from the atmosphere centuries ago, died, and froze before they could completely decompose. Worldwide, permafrost is thought to contain about twice as much carbon as is currently in the atmosphere.

Bruce and Neal have mapped the extent of that near-surface permafrost in Alaska and looked at whatís happening to it as the Arctic warms at a rate that scientists say is twice as fast as other parts of the planet.

Welcome Bruce and Neal.

BRUCE WYLIE:

Thank you, Steve.

NEAL PASTICK:

Thank you, Steve, for the opportunity to be on the show.

YOUNG:

Bruce, tell us what near-surface permafrost is, how far in the ground it goes?

WYLIE:

 Permafrost by definition is ground that has been below freezing for at least two consecutive years. And we define near surface permafrost if the top of that permafrost is within one meter of the surface. Google it, youíll see that thereís up to 2,000 feet below the surface of the ground up on the North Slope of Alaska. But generally, we would see, Iíd say 30, 40 meters from where our studies were. We were seeing areas that look like it may go down 200, 300 meters in certain areas, but we donít know. Got to get a drill rig out to the middle of nowhere to do that. 

YOUNG:

So you to field work to kind of gauge the depth of permafrost and near-surface permafrost. Neal, tell us a little about that.

PASTICK:

We typically conduct field work in Alaska during late August or September, not only because the mosquito populations have begun to dwindle and itís really the nicest time of year, but also mainly because the seasonally frozen ground is fully thawed. So what weíre really after is quantifying the depth to which the top of the permafrost is at, or perennial frozen ground. So, when we head out to the field, we typically lay out a transect at a scale thatís equivalent to those remote sensing inputs that weíre using. And along this transect, weíll take a metal tile probe, really scientific, to quantify the depth to the top of the permafrost. And it just involves inserting a metal rod into the ground until thereís some refusal. And when we hit the top of the permafrost, thereís a thud. So, really scientific method to do it, but itís a tried and tested and proved method that a lot of scientists have used in the past.

YOUNG:

And tell us how you can map permafrost from remote sensing platforms. I mean how do those things tell us where the permafrost is and how deep it is.

PASTICK:

Yeah, so what weíll do is take those field observations then an intersect it with our remote sensing data, or other geospatial data with factors known to reflect or explain the distribution of permafrost. So, like historical climate data. Something weíll feed into these models. Vegetation maps. Etc. etc. And basically once we have this database, we use computer algorithms or machine learning algorithms to upscale those observations using those relationships across the larger landscape.

YOUNG:

Bruce, have your studies been finding that permafrost is disappearing?

WYLIE:

Our studies initially were primarily focused on making the best darn permafrost map that we could. And so we did that, mapped it at 30 meters. The whole state of Alaska. There are other people that have more long-term sites looking at if the permafrost is degrading. And many of those look at the temperature of the permafrost, and those studies show that the permafrost is indeed warming and approaching a melting point in many places. We can repeat this on all of our survey lines across Alaska to document conclusively how permafrost has changed over time.

YOUNG:

Neal, what is the significance of that loss?

PASTICK:

The significance ... well, permafrost is the foundation for which most everything is built on in the Arctic, right? So, imagine your house and removing the infrastructure underneath your house. Everything would collapse. So in ice rich soil, or permafrost that is high ice rich content, once that thaws, the ground surface can collapse, causing damage to infrastructure, homes, and complete reorganization of vegetation communities on the surface. 

YOUNG:

Bruce, what happens when permafrost changes?

WYLIE:

Bruce: Well, a lot of the permafrost, particularly if itís near-surface permafrost, has a pretty direct impact on the plants. So if you have permafrost, itís almost like having bedrock at about, like, less than a foot sometimes. And so, guess what, you have a perched water table. Itís going to hold that water right near the surface. And the black spruce trees that dominate this boreal system are shallow rooted. If you lean on one, you can almost push it over, and itís a 300-year-old tree thatís as big around as a broomstick. But theyíve got very shallow roots. And youíve got moss. Itís like walking on, you know, 20 down comforters stacked on top of each other. Itís just squishy mossy stuff. And so that kind of system would be in jeopardy with thawing permafrost. The active layer or that maximum thaw depth would get much deeper, and it would facilitate more water seeping into the soil and more lateral movements of the water through the soil. And maybe even facilitate water movement down into the aquifer. Studies have shown that that would tend to make a drier system, which may be more vulnerable to fire.

YOUNG:

We have heard that there is a lot of carbon that is quote, in the freezer. What happens to the carbon when that permafrost is no longer there, and how significant is the escape if it escapes?

PASTICK:

Thatís a really good point, right? So, once permafrost thaws, itís previously frozen organic matter can start to decompose and be released to the atmosphere in the form of carbon dioxide and methane. Really depending on the soil respiration that takes place. This microbial decomposition and subsequent release of greenhouse gases to the atmosphere can actually accelerate climate warming, which in turn results in more permafrost degradation, which is creating a positive feedback loop, which can impact societies in and outside of permafrost-effected areas.

WYLIE:

One of our researchers is Mark Waldrop at Menlo Park, and he actually looks at microbes with DNA of the soil to see what kind of microbes there are. One of his papers, he found that the microbes that are in the permafrost, when they thaw, theyíre ready to go and they land running. And so they start decomposing that stuff as quick as they can. When you freeze something, you can kind of break the cellular structure because the freezing of the cellular water, cytoplasm, will expand. So when it thaws, things tend to decompose quite quickly. Whatís going to happen to it? The carbon in the permafrost will decompose, whether it decomposes in the presence of oxygen or not in the presence of oxygen. Not in the presence of oxygen might be under a wetland or in a really wet situation. Without oxygen, youíll get methane, and thatís five times as potent of a greenhouse gas as carbon dioxide. If it decomposes with oxygen, you get carbon dioxide, which is a major greenhouse gas. 

YOUNG:

You apparently with your work and the work of your collegues have been able to project near-surface permafrost extent into the future. How do you do that, and how do you know, unless time goes by, that your projections are accurate?

WYLIE:

You know, I talked about our first objective was to make the most accurate map as we could of permafrost. And to do that, we had lots of observations around Alaska, at different years and different times and stuff. And then we used that regression tree model with spatial inputs. Several of those spatial inputs were current climate, current precipitation and current temperatures. So, we had already had a model developed that used climate as an input. All we did was then make a map with that model, but this time instead of putting current climate, we put in future climate or future climate scenarios and then just made a map of it. The weakness of this approach is we assume the land cover is constant, right? We didnít change the land cover. We didnít change anything like that. So if the fire frequency is going to increase in the future, ours didnít capture that. Ours was just isolating the effects of a change in climate on permafrost.

YOUNG:

Whoís likely to use that kind of information, do you know?

WYLIE:

The process-based modelers that do the future climate projections will have a much better spatial representation of where permafrost is and where it isnít than what they had before. 

YOUNG:

Whatís the implication for the rest of the planet if the Arctic and Alaska are losing their permafrost. If itís degrading. If thereís more fires? Have those connections been made or not?

WYLIE:

The high amount of carbon stocks in these high latitudes is quite impressive. If you look at the UNEP (United Nations Environment Programme) map of soil stocks, youíll see that the Arctic even has higher carbon stocks than the tropical forests. Thereís one area I saw, Indonesia, that may have a little higher carbon stocks than the Arctic. But the Arctic has a very large land mass. Itís all of Siberia, Alaska, just huge. So the potential amount of carbon that could be released in Alaska is significant. 

YOUNG:

Neal, how do you mitigate against permafrost thaw?

PASTICK:

So when youíre building these different infrastructures, you can put in self-leveling systems as well as have these ... like theyíve done with the pipeline, is have these cooling pipes that are planted into the ground that keeps the ground frozen even as air temperatures increase. So, those are a couple of different ways that you can mitigate permafrost thaw at the engineering level. 

YOUNG:

Youíve obviously been up in Alaska, youíve done field work. Do you ever encounter any wildlife up there? Do you have any stories to tell? I mean what do you do when you encounter a grizzly bear or something else?

WYLIE:

Weíve had black bears come into camp, and I shot them with a beanbag round to scare them off. But the most interesting one I think for your audience might be, we were floating down a river called the Hula Hula in the North Slope of Alaska and we were headed for the Arctic Ocean. We were going to be met there by a boat to come and pick us up. We were halfway, five days into a 10-day trip, and we were sitting around a willow fire ... thereís no trees there. And Neal looked up and he said, ëOh thereís a bear on the other side of the river.í Of course, every bear up there is a grizzly. And then he said, ëOh, and thereís another one, and another one.í My shotgun was a meter, a yard away. And I grabbed that, and then I stepped in front of the group. I didnít want anybody in front of me. And two of the bears ran off, and one charged down the ridge straight at us. Oh, it was beautiful. Just in awe. And then all of a sudden, oh no, heís coming for me! But they taught us, you know, you set your defensive perimeter, you know, 15, 20 yards. If they get within that, youíre going to unload. The willows on the other side of the river was my perimeter. I was going to start shooting. Fortunately the bear turned around halfway down. 

YOUNG:

Did it get your blood pumping or what?

WYLIE:

Oh, yeah. Thereís lots of stories I could tell.

YOUNG:

Weíve been talking to Bruce Wylie, a USGS scientist at EROS, and his colleague Neal Pastick, a physical scientist and contractor to the USGS, who have done years of study on permafrost levels in Alaska and how they are changing as the Arctic warms. 

We hope you come back for the next episode of Eyes on Earth. This podcast is a product of the U.S. Geological Survey, Department of the Interior. Thanks for joining us.