Baked Alaska: Alaskan Glaciers - Rivers of Ice and Indicators of Change
As global temperatures rise, they profoundly impact Earth’s largest reservoir of fresh water, glaciers. Outside of the Polar regions, Alaska has one of the largest accumulations of glaciers on Earth. US Geological Survey (USGS) Geologist Dr. Bruce Molnia discusses glaciers from across the Alaskan landscape and their relationship with climate and sea level.
Bruce Molnia: Hello, everybody. How are you?
I'm going to take the next 45 minutes or so and talk to you about how glaciers in Alaska are changing and some of the reasons that they are changing, but I'm going to begin by talking, first, about the Earth system, talking about water, talking about climate, talking about weather, and then focusing on glaciers. To me, they're all part of a continuum, which I'll try to describe to you.
And then we'll talk about what happens when water changes phase because that's what the biggest part of the impacts of changing climate are. If the water stays frozen as ice, then we don't have to worry about sea level changing, but as soon as the glaciers begin melting, the majority of the water ends up in the ocean. Depending on how much melt there is determines how much sea level change there will be, and depending on where you live and where your infrastructure's located, then there are either minimal or substantial consequences that are driven by climate change.
My title is "Baked Alaska", but I want to begin with the Earth system.
The Earth system is different from almost any other body within our solar system. What makes the difference is that water exists in the Earth system in three phases, gas, liquid and solid, and water is the primary component of all of the interrelated parts of the Earth system.
This is a slide that we put together probably 25 years ago when we started to talk about planets as systems.
The Earth system is made up of the lithosphere, which is the rock that is the core of this entire system, but in addition to that are two types of water components, a hydrosphere, which is liquid water, a cryosphere, which is frozen water, an atmosphere which has gaseous water in it, and then the biosphere which is the living component of this total system.
When you have this type of an arrangement of a lithosphere with these other types of spheres added to it, you get a complex interaction and dynamics that don't exist on any other body in our solar system.
For instance, if you were to look at our moon, we'd have a lithosphere, we would probably have a cryosphere because there's evidence that there's frozen water, we have a very, very weak atmosphere, no biosphere, and probably no hydrosphere. But the fact that we have all of these spheres interacting produces geochemical cycles, hydrologic cycles, and collectively lead to climate.
Earth has had climate for probably three billion years or more. The planet's four-and-a-half billion years old. And really, to have climate or the Earth to develop a defined climate, as soon as it had liquid water at the surface. In its early stages, most of the water either wasn't there, it was tied up in other chemical components, was in the interior of the Earth, but as the Earth started to differentiate and develop a hydrosphere on its surface and an atmosphere, it started to develop a climate. And climate's influenced by topography, by the rotation of the Earth, by solar activity, by any number of factors.
So the Earth has had climate, and one thing that you can say about climate is climate continuously changes. These interactions are characterized by this diagram which comes from the IPCC that shows the relationship between the lithosphere, the atmosphere, the biological co-components and the water components. For this presentation, we're going to focus on the part of the Earth's surface that is the interaction between glaciers, snow and oceans.
Weather is what we are dealing with today. We've got very cold weather, low temperatures, we had high winds yesterday. Weather is a set of physical parameters that exist at any particular location on the Earth's surface at any point in time. When we talk about weather, we're talking about basically these six characteristics: temperature, pressure, precipitation, humidity, velocity and direction of the wind, and cloud cover.
When we talk about climate, we're talking about long-term weather patterns, and typically we're talking about minimal of decadal types of weather patterns. Or we can talk about century scale, millennial scale, or even million-year climate. We talk about certain geologic periods being significantly warmer than today.
The difference between weather, which is what you get any point in time, and climate is significant. Climate is a long-term average. So if we say climate is changing from year to year we're really talking about weather changing from year to year.
You can get a tremendous amount of variability in weather. That's why some years it's extremely hot and some summers it may not be as hot. That is weather. If you had a 100-year record, you'd be able to come up with what a mean temperature would be, and then you'd be able to talk about variability within that range. That's what we talk about in terms of climate. We're talking about century scale and longer.
Now, are there any indicators that climate is changing? Many.
This is an interesting one. I was walking along a brand-new trail that they had just opened in the Mendenhall Visitor Center in August of last year and found this sign. It says, "Falling ice. For you own safety, do not go beyond the sign," which behind it is a dense alder thicket. The glacier, which is the Mendenhall Glacier, which probably was within about 250 yards of this sign when it was put in 40 or 50 years ago, is now three-quarters of a mile away.
What's happened is that that area which was exposed by the retreating ice has been colonized by vegetation, and now there are all sorts of insects and small mammals, birds, you name it. It's become a habitat, totally different from what it was less than half a century ago.
So what's the driving force in that? Well, it's a warming trend that is represented by these temperature measurements in Alaska that showed changes since the World War II end period, 1949, in this case I'd only brought it through 2006. You can see dramatic increases in the mid-'70s that represent almost 4 degrees Fahrenheit of warming in Alaska at what are now 19 first-order weather stations.
And you can see on a seasonal basis that spring temperatures are up almost 4 degrees Fahrenheit, summer, 2.3, winter, more than 6 degrees warmer. And this is all of Alaska. We're not just talking about Juno or Fairbanks or Anchorage. This is 19 first-order weather stations.
Now, let's talk about water. Water is a natural-occurring chemical compound composed of 1 atom of Oxygen and 2 atoms of Hydrogen. Each molecule of water has a set chemical and physical response depending on the temperature or the pressure that it's located at. When we freeze water, we get a mineral that's called ice.
Now if we looked at all the water on Earth and if we used 1,000 drops to represent where that water actually is, we would be very surprised, at least I was when I finally sat down and did these calculations, that 972 of those drops are salt water. They're in oceans, inland seas.
Twenty-one of those drops are glaciers. So think about that: between oceans and glaciers, you've got 973 out of 1,000 drops of water. About six drops are in the ground water and soil. Less than one drop is in the atmosphere. Less than one drop is in all the lakes and rivers. Think about where we get our drinking water from. And less than one drop is in all of the living things on our planet.
That 97.2% of salt water is the largest reservoir of water on Earth, but that 2.8% is fresh water, and of that, 75% is tied up in glaciers. Think about that. Seventy-five percent of all the fresh water on Earth is frozen water, is ice. Think about what that means in terms of availability of water. Also think about what happens when temperatures either increase or decrease.
We talk about glaciers being the 'canary of climate change', and they actually are, but they also are the main driver for what the impacts of climate change are on most human habitation. Since more than 60% of the Earth's population lives within 50 kilometers of the ocean, if the ocean changes either by going up or by going down, that produces dramatic changes. And I'll give you some examples in a couple of minutes.
Now let's define what we're talking about when we talk about glaciers. Glaciers are large perennial accumulations of ice. They also have snow, rock, sediment, liquid water all as part of their constituent. They move downhill under the influence of gravity and under the influence of their own weight.
They are formed by a complicated metamorphic process where snowflakes get compressed, re-crystallize and form ice crystals. The density of glacier ice is significantly graver than refrigerator ice or most other kinds of ice like ice because it's forming under great overburden pressure, so the air is driven out and it's almost pure water.
You can't compress water molecules, but you can eliminate the space between the molecules. In refrigerator ice, you may have 30% or 40% of the space between individual molecules filled with air; glacier ice, you don't.
Glaciers are literally a monomineralic rock composed of the mineral ice.
Glaciers are classified by their location, by their size, and by the temperature that they were created under. So we talk about polar glaciers, which are the glaciers in Central Greenland and most of Antarctica, and we talk about temperate glaciers. Temperate glaciers are glaciers where, at least for part of the year, liquid water is present in conjunction with or in contact with the frozen water.
Just by the physics of water, in order to have liquid water coexisting with frozen water, the temperature of the frozen water has to be significantly high, very, very close to the melting point, within, in fact, a small fraction of a degree of the melting point. Consequently, a small amount of temperature change has a significant amount of impact on melting of that ice.
On the other hand, if you're talking about polar ice, the mean annual temperature at the South Pole, where there's 10,000 feet of glacier ice, is about minus 60 degrees Fahrenheit.
So it's very hard to comprehend that any kind of change in Earth processes would result in any significant melting at the South Pole even if you were to warm it by 50 degrees. Even if you were to warm it by 75 degrees, you'd still have glacier ice well below the freezing point. In fact, the last time the Earth's climate resulted in a loss of glacier ice at the South Pole was about 20 million years ago.
I sort of preempted this discussion by talking about the polar regions, but you can see here is Greenland and here is Antarctica. You can also notice that glaciers span virtually the entire north-south area from north of the Arctic Circle to almost the Antarctic Circle.
So we have glaciers in North America that are in the high 60s to low 70s degrees of latitude, we have Arctic glaciers in Canada that are above 80 degrees, and we have subpolar glaciers in the southern hemisphere that are down in the high 60s. In fact, the Antarctic Peninsula gets up above the Antarctic Circle. So we have glacier ice that is temperate ice that spans the entire region from north of the Arctic Circle to south of the Antarctic Circle.
Let's use another analogy. If there were 1,000 ice crystals on Earth, 914 of them would be in Antarctica, 79 would be in Greenland, so you're looking at 973 out of 1,000 being in the polar regions, and then four in North America with about one in Alaska, two in Asia, and less than one everywhere else on Earth.
So when you talk about temperate glaciers, which up until recently has been the only source of meltwater going into the polar oceans, it really is an inconsequential amount of water in terms of the big picture that's tied up in temperate glaciers.
And as you'll see in a couple of minutes, if we were to melt all the temperate glacier ice on Earth, the maximum amount of sea level impact would be less than a foot. So when you start talking about what happens if polar glaciers begin melting, that you get dramatic differences in where sea level is today as opposed to where it might be in the next century.
Just going back to reiterate, 91.4% of all the glacier ice is in Antarctica and 7.9% is in Greenland. The remaining seven-tenths of a percent is in North America, South America, Europe, Africa, Asia, New Zealand, and on the island of Irian Jaya, which is Indonesia and New Guinea, so the glaciers that straddle the equator and go all the way up to the high 70s and 80s.
I've already defined what a temperate glacier is, but I want to emphasize this again: small change in temperature can have a dramatic impact on what happens to the area, the volume of those glaciers, and on sea level. More than 95% of the glaciers in Alaska are temperate, and that's where this comes together when we talk about how glaciers are changing throughout Alaska.
Let me digress for a second and mention that in the rest of the United States, there is probably close to 500 square miles of glacier ice. About 80% of it is in the state of Washington, but glaciers exist in Nevada, Utah, Colorado, California, Wyoming, Montana. There may be one glacier left in Idaho. But what fascinated me, there's still one glacier left in Southern Nevada, in Great Basin National Park on Wheeler Peak.
These glaciers span latitudinal ranges from the low 30s to the high 70s in North America in the United States.
So what's the impact of glaciers on sea level change? The term that we refer to, we talk about 'eustatic sea level change', which talks about changes in global sea level. There are two primary causes for changes in global sea level: one is a change in ocean water volume, one is a change in ocean water temperature.
The temperature becomes an issue because as you heat water molecules, they expand, so the same one water molecule takes up more space at 75 degrees Fahrenheit than they did at 65 degrees Fahrenheit. So you can have sea level rise without having any new water enter the ocean. We refer to that as 'steric sea level rise' and that is responsible for about half of the sea level change that's taken place since the Little Ice Age.
Little Ice Age is a period of time that ended in the last 150 years when glaciers on six continents expanded. Since the end of the Little Ice Age, which was anywhere from between the 1750-1760 time period, and in some cases the early part of the 20th century, glaciers on every one of those six continents have decreased substantially in area and volume.
Let's go back in time, though, and talk about the end of the great Ice Age during the Pleistocene, during the last glacial maximum. About 8% of Earth's surface was covered by glacial ice. That's 25% of the land area and about a third of Alaska. To put this in perspective, in order to have that much ice on the surface of the Earth above water, the global ocean was down by about 400 feet.
So if you were standing in Ocean City today at what is the present shoreline, and we're looking now towards Europe, you wouldn't be able to see the shoreline of the 20,000-year-ago time period because it would've been 60 miles further to the east. The same is true in California, but not that great a distance. In Northern Alaska, there are another 300 miles of area added to the continental shelf because the Arctic continental shelf is extremely shallow.
So if you look at a map of the land area of North America during the last glacial maximum, North America would've been about 15% larger in land area. Today, let's look at the numbers, about 3.1% of the Earth's surface is covered by glaciers, about 10.7% of the land, instead of being a third, it's now a tenth, and only about 5% of Alaska.
Beginning about 15,000 years ago, continental glaciers began melting, and for 10,000 to 11,000 years sea level rose. It rose 400 feet between about 15,000 years ago and about 6,000 years ago, and since 6,000 years ago, the level has fluctuated up and down, some places up to half a foot, some places as much as a foot and a half, depending on local tectonics and a number of other parameters that are more regional rather than global.
Now what would happen if we started melting today's glaciers? If you were to melt all the glacier ice in Alaska, sea level would change by about two inches. If you were to melt all of the temperate glaciers on Earth, sea level would rise by about a foot. If you melted Greenland, you're looking at about 20 feet. And if you melted Antarctica, you're looking at 240 feet.
I mentioned this earlier, the last time Antarctica was ice-free was about 20 million years ago. The last time Greenland was ice-free was about 110,000 years ago. At that point in time, the shoreline in Virginia would've been out at the Fall Line, would've been out by Leesburg.
So we've had tremendous variation in where the shoreline is at any point in time over the last hundreds of thousands of years. During the Pleistocene, glaciers have increased in area and decreased in area and they've increased in volume and decreased in volume.
This is not going to happen, but if all of the glacier ice on Earth were to melt, sea level would go up about 80 meters, about 265 feet. None of the present climate models predict anything like this.
What they do predict... Let me back up a little bit and say these are some of the observations. During the 20th century, sea level rose at an average rate of about a 20th of an inch to a tenth of an inch per year, and this equates to a global sea level rise of between five and nine inches during the 20th century.
The IPCC expresses a high confidence, this is the way they rate things in the IPCC report, that the rate of observed sea level increased from about the 1850 period to 1950, that at the end of the Little Ice Age, which for more points is around the middle of the 19th century, the rate of sea level rise increased, and that was directly correlatable with the melting of these temperate glaciers on all of the continents that we described possessing glaciers.
Tide gauges don't show that same acceleration. Now tide gauges tell you what's happening at individual locations, and there's very little correlation from tide gauge to tide gauge from one area to another because each area, for instance, has its own local tectonics, has its own local settling of sedimentation. There are any number of factors that impact local sea level.
Satellite measurements, which began in the mid-1990s, show a rate that's been higher than the tide gauges. This is for the global ocean. The IPCC estimates that by 2100, global average sea level will rise anywhere from about half a foot to close to two feet. This is a graph that shows sea level change from 1800 to what might be anticipated in 2100, and as you can see, there is a definite anticipated increase in the rate of sea level rise.
And then there's this asterisk. For those of you who are familiar with sports, asterisks always indicate something out of the ordinary, and typically it has to do with steroids. But in this case it doesn't.
In this case it has to do with glaciers on steroids. Maybe it does. This has to do with the fact that many glaciers in the polar regions are now being observed to have more meltwater at their bases, at their beds, where ice contacts bedrock, than previously had been observed. And what this is doing is causing an acceleration in ice velocity so that you may have read some glaciers in Greenland flowing up to five or six times faster than they had pre-1995.
In Antarctica, this is coupled with the loss of floating ice shelves, which acted as a break for some of these high-latitude, let me say it different, northernmost Antarctic glaciers. You have to remember, Antarctica is fairly southern, almost 68 degrees to 90 degrees south, but in the northern parts of Antarctica you're getting into latitudes where the glaciers start acting as if they were temperate glaciers. And if you take away the floating ice shelves around the Antarctic peninsula, you actually get a significant acceleration in the amount of ice flow.
So this asterisk represents studies that have been done in the last three years that are suggesting that there may be a significant increase in the amount of water coming from the rapid flow of Antarctic glaciers into the ocean, causing that 'up to two feet' to change by 'up to two meters', so two feet to up to six-plus feet.
No one is certain as to whether that's a reality or a short-lived phenomenon that we're observing, so stay tuned. If I were to give you this talk in 10 years, I might have a little bit more concrete information about it. But this is the IPCC report and they clearly state in the IPCC report that their estimates do not include these catastrophic types of changes, although they were aware that they may be happening.
Having said that, we spent about 20 minutes sort of setting the framework. Let's spend the next 20 minutes talking about glaciers in Alaska.
We know a lot of about glaciers in Alaska for a number of reasons, but the one that I'm most interested in is the visual documentation of glaciers and how they have changed.
This is the first photograph I've been able to find, the earliest, that shows the Muir Glacier in what is now Glacier Bay National Park in 1883. What we have in Alaska is a photographic documentation of in some cases more than 125 years of landscape evolution and change.
Now, Little Ice Age glaciers in some parts of Alaska began to retreat about 1750. That was the case in Glacier Bay. Other parts of Alaska, they only started to retreat in the late 1880s, 1890s. So some places, we have total documentation of how the glaciers have responded from their Little Ice Age maximums. In Glacier Bay, we've got 50%.
We have aerial photography in Alaska that dates to 1926, surprisingly quite early considering how remote Alaska was, but there was a USGS survey that took more than 50,000 photographs in 1926 and 1929 and included all of Glacier Bay.
Since the 1970s, we have satellite imagery covering all of the land surface of Alaska, so we've got multiple images. Here's just one example of an area that was shown in that 1926 aerial photograph. This is the same location as in the satellite image. This is a LANDSAT image from 1984.
So we have ways of looking at glaciers, from oblique, on the ground, from the air, and from vertically above, that tell us quite a bit about their extent. And by taking cartography, GPS and any other number of surveying techniques, we can do quite a good job of reconstructing how much ice was located in different areas, how large the glaciers were at their Little Ice Age maximum, and how much ice has been lost.
To give you an example, in Glacier Bay National Park, we've lost more than 1,000 cubic miles of glacier ice since 1750. I'm sorry, in Glacier Bay National Park, we have lost 1,000 cubic miles, more than 3,000 cubic kilometers, of ice. That's a phenomenal amount when you think...and we'll put that in perspective in terms of how much ice actually exists in Alaska today, but that's a really amazing thing. It's more than 5% of the total ice volume in Alaska.
When you put all of these types of information together, you can actually come up with a fairly comprehensive story about glaciers in Alaska. And I've done that, and the result is this USGS professional paper that came out October 2008 called "The Satellite Image Atlas of the Glaciers of the World", the Alaska chapter, and this is a copy for the museum.
When you look at Alaska, you discover the 14 different geographic regions that support Alaskan glaciers. And we'll talk about them in terms of how they're changing.
Of these 14 different geographic regions, there are more than 50,000 glaciers, most of which are small glaciers in higher elevation, and they cover an area of nearly 30,000 square miles. So when you talk about Glacier Bay losing more than 1,000 square miles of ice, that's a significant percentage of all the ice that had existed in Alaska. Of these more than 50,000 glaciers, about 2,000 are valley glaciers. Even though we know exactly where there are, only about a third of them have been formally named.
Now when you compare the glaciers of Alaska with the rest of the world, glaciers of Alaska have about one-third of the glacier area of Canada. Canada has a large amount of Arctic glacier ice. But when you compare them to the rest of the world, Alaska alone has about half the glacier area of all of Asia.
I've been reading a number of reports talking about the Himalayas as being the major temperate glacier reservoir. The reality is, it's about the same as Alaska; when you look at other parts of the world, six times the glacier area of Iceland and Alaska, about 75 times the glacier area of New Zealand, 12 times the glacier area of Europe, about 100 times more glacier ice than the rest of the United States. So Alaska is quite significant.
But again, if you remember my number before, if you melted all the glacier ice in Alaska, you'd have less than about two inches of sea level rise. I'll give you some idea of how dramatic and expansive glacier ice is elsewhere on Earth.
Glaciers in Alaska range in size from very small, barely the size of a football field, to two glaciers, the Bering and the Malaspina, which are each more than 2,000 square miles. In fact, if you were to take the Bering Glacier and drape its outline over a map of the eastern United States, it would go from Philadelphia to the White House lawn. If you do that in California, it would go from Santa Barbara to the Mexican border. It's huge. And the volume of water today in Alaska is about 12,000 cubic miles tied up in glacier ice.
So what's happening to the glaciers in Alaska? Throughout Alaska, nearly all lower-elevation valley glaciers are experiencing significant retreat. They are thinning, they are stagnating, meaning they are wasting away in place, especially at these lower elevations.
In fact, if you were to look at those 2,000 valley glaciers, more than 99% of them are showing visible evidence of decrease in area, volume and life. Many small cirque glaciers, and these are glaciers at lower elevations up to, say, 7,000 or 8,000 feet, have completely disappeared, as have many small valley glaciers.
However, just to make things interesting and to show you how complex local variability can be even when you can have a regional climate pattern, there are about a dozen large glaciers in Alaska that are advancing, and not just by expanding by spreading their volume over larger areas. They are expanding by increasing in total volume, total length, and total area. Several of them have been growing from more than 200 years continuously.
At higher elevations in Alaska, there's very little change. At some locations, we're actually seeing an increase in the total volume of ice above 6,000 or 7,000 feet, but it's not translating to increasing the lower parts of the glaciers. So we're seeing an increase in melting due to that temperature change that I showed you at lower elevations whereas no change at the higher elevations where temperatures may be increasing slightly but not enough to have an impact on changing the phase of the water.
At many locations in Alaska, this change has begun in the middle of the 18th century, so long before the Industrial Revolution. So there are any numbers of interesting observations that we can make about Alaska that play a role in determining the complexities of climate change, the variabilities of climate change, and the fact that you just can't generalize and say, 'Oh, yeah, the glaciers are all disappearing. Oh, yes, it's warming,' because that's a good, simple three- or five-word statement, but if you really want the answer, it takes paragraphs and sometimes it takes a pretty long period of time to get into the local variability.
And now I'm going to start talking about local variability.
This is what we'd like to see in Alaska. We'd like to see thick snow accumulations. This is an accumulation from the 1980 time period on the Mendenhall Glacier and its upper reaches where in one winter there was more than 15 feet of new snow that lasted into summer.
What we see more often, and this is the lower reaches in the Mendenhall Glacier about three years ago, is bare ice with no snow from the previous winter and lots of liquid water indicating that the ice is melting. So not only do we lose the complete previous winter snow cover, we're seeing older ice also melting away.
In fact, there are many places you can go. This is the Guyot Glacier in Icy Bay, Alaska, which is part of Wrangell-Saint Elias National Park. In fact, let me clarify that. This is the boundary of Wrangell-Saint Elias National Park, this is Federal Bureau of Land Management land. The way the park boundary is defined is the terminus of the glacier. So there have been several times when this park has gotten larger, and presently it's getting smaller.
But here you're seeing glacial meltwater going directly into salt water. And this is what happens in most parts of the Earth so that human use of that water is not possible.
This is the book I talked about. It deals with what I'm going to present now, the 14 regions as how this book is organized. There's also a website which, I'll show you the homepage for it, the URL is on top, www.usgs.gov/global_glaciers, which goes into much of the detail I'm presenting here but also focuses on Kenai Fjords National Park and Glacier Bay National Parks showing for almost every one of the large glaciers how they've changed over the last 100 or so years.
Now just to document simple visual evidence of climate change. Just watch, there are going to be four pictures here.
This is the mouth of Muir Lake in Glacier Bay. The first photograph is an 1899 photograph from the Harriman Expedition by Grove Karl Gilbert. This photograph's picture I took in 2003. In fact, the only ice in the picture is all the way over here on the right-hand side, and that's Riggs Glacier, which was a former tributary to Muir Glacier that you saw in this photograph.
What we're going to do is take a look at how other regions of Alaska are changing. Again, these are the 14 geographic regions. I've broken them down; this group of eight are regions where every single glacier that has been observed is shrinking.
Here are the regions. We're looking at as far north as the Brooks Range all the way down to Kodiak Island and the Aleutian Islands. So here there are thousands of glaciers, every one of which is showing conspicuous loss of area, volume and length.
Some examples. This is McCall Glacier in the Brooks Range, second-largest glacier there, photographed here in 1958. You can see that even in 1958 there is evidence, this is called the trim line, that the glacier had recently been much larger. Here it is photographed in 2003. So here we are 47 years later and the glacier has thinned in this case by more than 75 meters and retreated by several hundred meters. This is typical of every one of the 600 glaciers in the Brooks Range.
Another example. This is the largest glacier, the Okpilak, photographed in 1910 by Leffingwell. He was a USGS researcher, one of the first mapping in the Arctic. Same location in 2004.
When we look at Kenai Fjords National Park, here we have a picture that U.S. Grant, who was, again, a USGS contract geologist, took in 1909. Same location of that photograph in 2004. Another one of the large glaciers in Kenai Fjords, the Holgate. Again, 1909, 2004.
If we move to the westernmost part of Alaska, the Kigluaik Mountains. This is a photograph that was taken by Darrell Kaufman in 1985. This is the last glacier there, the Grand Union Glacier. In the 1950 time period, there were three periods that were mapped, two of them completely melted away between 1950 and 1985. This moraine, this large amount of rock that you see around it, gives you some idea of how large it was when it was at its Little Ice Age maximum, probably 200 years prior to this photograph.
Talkeetna Mountains, which are just north of Anchorage. This is the Talkeetna Glacier, the largest glacier in the Talkeetnas. This is where it was in the 1950s where the color changes from sort of tan to dark. Down here, there is a ridge that represents where it was in the 17th, 18th century. So again, every glacier in the Talkeetna Mountains is retreating between 1950 and 2002, when they were mapped twice by the USGS. About 25% of the smaller glaciers disappeared.
The Wood River Mountains, also in western Alaska. This is one of the glaciers that was photographed and studied by the IGY, 1957 to 1959, the Chikuminuk Glacier. Its Little Ice maximum position is down here. Its 1957 position is here. Its 2005 position would be about right there. Of eight glaciers that were mapped by the IGY, every one of them is rapidly retreating. This one is the fastest in its rate of retreat.
Another example of a small glacier. This is also in the Wood River Mountains. This is bedrocking; you can see waterfalls coming off of it. The ice was down here. Here is its end moraine from the Little Ice Age, and it's well back here. This is what you see with 99% of Alaskan glaciers.
In other places like the Alaska Range and the Wrangell Mountains, what we see are glaciers at higher elevations aren't changing much because they've got significant elevation. The Alaskan Range goes up to 20,000 feet, the Wrangells go up 15,000-plus feet.
Their mean annual temperatures above, say, 12,000 or 13,000 feet, are well, well, well below the freezing point. In fact, at the summit of Mt. Wrangell, the mean annual temperature is minus 40 degrees C, which by coincidence is also minus 40 F. There, there has been no glacier melt because of climate change. Temperature hasn't changed there at all.
But here in Denali National Park, this is a photograph that USGS geologist Stephen Capps took in 1919, and one of my Parks Service colleagues took in 2004, showing an unnamed glacier in the Teklanika River Drainage Basin. Again, there's been more than 500 feet of thinning and about two-thirds of a mile of retreat. This is typical of what you see throughout Alaska.
However, in the Aleutian range, the Chugach, the Coast Mountains, and the Saint Elias Mountains, we get mixed messages. These are where the dozen or so glaciers out of several hundred are currently advancing.
So to characterize, again, more than 95% of the larger glaciers are on retreat, but it's this other 5% that really creates some interesting stories.
Talking about some of the retreating ones, this is the largest glacier in Alaska. This is the Bering Glacier. This is a satellite radar image showing it in 1990. What I want to point out, this was the perimeter of the glacier in 1900. It came all the way down close to the Pacific Ocean down here, but this large black area, which is now an ice-marginal lake, was completely filled by glacier as recently as about 110 years ago.
Since then, it's lost about 2% of its area. Now this glacier is 5,000 square kilometers, so it's lost more than 100 square kilometers during the 20th century. But it is still a significant amount of ice left, and we're looking at elevations that are close to sea level.
But just let's look at the last decade-and-a-half or so. Here are two recently-declassified spy satellite images from National Systems showing the Bering Glacier in 1996 and then in 2005. During this time period, this part of the glacier here has disappeared, and we've had a maximum of nearly four miles of glacier retreat in a period of only a decade.
This is an oblique photograph I took of the Bering in 2002 showing one of the reasons why it's retreating as rapidly as we've measured it to be, and that is that it almost has no gradient, its terminus is floating so that liquid water is able to get into every crack, and it just causes these big pieces to slowly separate and drift away.
This type of behavior, which I refer to as 'disarticulation', is quite common in Southern Alaska, the more than 50 large glaciers which have thinned to the point of floatation and are just slowly producing very large, in some cases more than a kilometer square, pieces of ice from their terminus.
This is an area that was a former tributary to the Bering Glacier. Here's the Bering down here. This color of trim line in the lower midround here is about 1940 or 1950 elevation of glacier, so it's thinned significantly in that last 60-plus years, but these are three separate valley glaciers that used to be tributaries, that used to come in and contribute to the flow of the Bering Glacier, and they now no longer make contact with the large, with the Bering.
This is the terminus of Tana Glacier. It's a glacier in Wrangell-Saint Elias National Park that has become more of a body of water than a glacier. This line that you see on the side of the mountain is the thickness of the ice about 1950. In 1950, there was a continuous ice margin that came all the way around like this. Now, you can see some floating ice, there's some places where ice is exposed on the sides of these what we call 'thermokarst lakes', but for the most part, we're looking at in situ stagnation.
Other areas. Here we are in the Chugach Mountains. This is Toboggan Glacier in Prince William Sound, a photograph again by U.S. Grant, 1909.
What I find interesting in this photograph, when you look at the picture, you can see there is a large what we call 'barren zone' or trim line on both sides of the glacier. In 1909, it was significantly retreated from where it had been in the middle of the 19th century. But then when you look at where it was in 2000, it's actually just barely visible over here on the edge of this sloping ridge, and everything that was bare bedrock at the beginning of the 20th century is now heavily vegetated at the beginning of the 21st century.
So it's one of the other observations that we've made. It leads to the conclusion that there are significant changes in the glaciers. They're retreating, but there's also an even more formatic change in the habitat and the adjacent ecosystems. The ice retreats, the vegetation comes in very quickly, new bays form as the glaciers retreat, new large lakes form, and very, very quickly we end up with a situation where there is a totally different type of an environment.
In some places, it's deleterious to marine mammals. For instance, there is a whole population of birds and marine mammals that need floating ice in fjords adjacent to glacial termini in order to survive. As we're losing tide water glaciers, we've gone from more than 200 to less than 50 in the last 150 years. That habitat is disappearing.
So birds like the Kittlitz's Murrelet are running out of locations where they can find food and where they can nest, and many marine mammals such as harbor seals need the floating iceberg pieces in order to haul out for molting and also they need them in order to give birth to their pups.
Here's an example of local variability. This is Yale Glacier in Western Prince William Sound. This picture, which was taken in 2001, when I took it I was standing on where the terminus was in 1900. So you can see the dramatic retreat.
Immediately adjacent to it, the next fjord to the west is Harvard Glacier. This is where Harvard Glacier was in 1909. Same location for the 2000 photograph, Harvard has advanced and thickened and is almost two-thirds of a mile further advanced than it was in 1909.
So you get two glaciers side-by-side acting differently. To make it even more interesting, Harvard is the westernmost, Yale is in the middle, and a glacier called Meares is to the east. Meares is also advancing, so you've got two advancing glaciers bracketting the rapidly-retreating Harvard.
South Sawyer Glacier, I believe, is in Tongass National Forest. This is what it looked like in 2002, and the exact same location in 2006. Notice the change it retreated, almost two-thirds of a mile, and thinned by more than 400 meters. But between 2006 and 2009, very, very little change.
So there are lots of interesting variabilities and dramatic...some things happened very rapidly and then some things happened very, very slowly. A single glacier may experience different rates of change depending on its local elevations, bedrock configuration, water depth, and any number of other factors.
Some glaciers like the Taku are advancing. This one has been advancing continuously for more than 125 years. Others that are not very far away like the Mendenhall have been retreating rapidly in the last 50 years but have been retreating for more than 200 years.
In fact, when you look at the Mendenhalll, this is as far as it got in the 1750s all the way here at the very right-hand side of this image. What you see here in white, those are rooftops on houses. What you see here in green is the hummocky topography that was much more difficult to build on, so there's very little in the way of human habitation there, but that corresponds to the end moraine of the glacier. Everything between here and here are a series of recessional moraines that characterize how far the glacier had advanced.
By about 1940, it got to this point. The glacier spanned this entire area and it retreated into part of its valley that was overly deepened because of multiple advances and retreats in the past. When it did that, it was very quickly surrounded by water and the transition from just melting to capping icebergs.
So its rate of retreat increased by half in order of magnitude not because of change in climate but a change of its own local circumstances. And it's retreated back to this point where it's now so thin that it's floating and it's beginning to produce these large tabular pieces of ice that I described to you.
So in a single retreat cycle, this glacier has not only experienced the driver which was warming that created the initial response, but the interaction with its own environment has caused variations in how it's responded over the last 200 years.
If you go into the interior of Southcentral Alaska, you'll see lots of glaciers that look like this. They have well-defined lateral moraines that indicate how large they've previously been. Here is the terminus of the glacier. In this particular glacier, which was photographed in late August, the snow line is retreating very rapidly up-glacier, but its 1950 terminus was about here, its Little Ice Age terminus was about here.
You get some very interesting exceptions. This is Lituya Glacier. This is Lituya Bay along the Gulf of Alaska. This is on the western edge of Glacier Bay National Park. This glacier was back here around 1800 when it was first mapped by the French explorer Laperouse, began advancing after he left, and has been advancing continuously.
However, this line right here is the 1600 A.D. trim line. This glacier prior to its retreat before 1800 actually filled this entire bay and stuck out into the Pacific Ocean. So this glacier went through a major thickening during Little Ice Age, then had a catastrophic retreat, and has been re-advancing for the last 200-plus years. Again, some examples of local variability.
Here is a photograph of the glacier from this last summer. Just comparing the two which are five years apart, it's continuing to produce a huge amount of sediment, which is protecting it from calving, so that is how it has been growing more rapidly today than it did 50 years ago when its terminus was actually adjacent to open tide water.
Harvard Glacier, you may have heard about, has twice closed Russell Fjord by advancing and blocking this entrance, once in 1986, the last time in 2002. It causes Russell Lake to develop here. As the water level rises in Russell Lake, it puts a tremendous amount of pressure on the ice and eventually causes the ice dam to fail. When that happens, a huge amount of ice gets washed away and it takes several years to decades for the glacier to continue to grow to get to the point where it will close the fjord again. This summer, it came within 250 feet of closing it and probably will close at some time in the next few years.
This is the largest piedmont glacier in Alaska, the Malaspina, which is located not very far away from the Hubbard. In fact, the Hubbard is just on the other side of Yakutat Bay from here. This glacier has been thinning about three to four feet a year for the last 150 to 200 years. Again, you get this local variability and quite dramatic differences.
So I've taken 50 minutes, and I think I'll stop here, but let me just tell you a couple of little things about Glacier Bay. This is the Park Service brochure that shows the changes in Glacier Bay from 1750, when it extended all the way down to the mouth of the Bay, to the present. You can see there are two arms, east arm and west arm.
I've got one animation that I want to show you that will put in perspective the dramatic changes in Glacier Bay. 1750, 1850, 1890, 1937, 1964, 1985, and this is a satellite image showing what the Bay looks like today. One of my colleagues who has worked in the Bay for more than 50 years said, "It's time to rename the bay from Glacier Bay to Timber Bay." As you can see, most of what was covered by glacial ice 250 years is now covered by vegetation.
I'm going to use this as my last slide, but it characterizes the life history of glaciers in Alaska at the current climate environment that they are responding to. As temperatures are increasing, the glaciers are retreating. As the glaciers retreat, new environment becomes exposed. It quickly becomes vegetated. The vegetation serves as the anchor for any number of different species of birds and other quite diverse species of plants, insects, mammals, fish, come in and the change is dramatic.
And where we used to think that it took hundreds of years to get to a mature forest following a major climate event, what we're discovering is that in places like Glacier Bay where there was some refugia for seeds to continue to exist either just outside the Bay and areas that weren't covered by glacial ice or higher elevations where the glaciers didn't rise up to, as soon as the ice retreated, the seeds got blown in, took hold, and within decades we've got spruce growing in places where through normal succession it would take 300 to 400 years.
To summarize very quickly, Alaska is a dynamic region. It's one of the places that the changes in climate and the influence on sea level are all coming to the forefront and it's a place where we can continue to learn quite a bit about the impacts of changing climate on the natural environment.
Thank you very much.
Bruce Molnia: I've got time for questions, and I'd be happy to answer any questions that you might have.
No. They're growing in volumes, so it has nothing to do with bed friction. If it were only a change in area because they were spreading what was already there, bed friction could have been a factor. But they're getting thicker as they're getting longer, so no.
What I believe, and almost all of these fit this type of description, all of the advancing glaciers are located within about 50 kilometers of the Pacific Ocean. All of them have major tributaries that extend up to 12,000 14,000, 15,000, 18,000 feet depending on where they're located, so they have high accumulation areas that are located close to an abundant moisture source. So you get huge amounts of precipitation at the higher elevations, and the areas are great enough that the new ice that forms can overcome the amount that's being melted at the lower elevations by increased temperature.
So in that one instance where you had Meares, Yale and Harvard, even though Yale and Harvard both originate almost from the same mountain, Harvard has a much larger part of its total area at a higher elevation. Also, their orientations of the events was typically aren't due south-facing, so they're probably getting less influence of solar energy melting newly-fallen snow.
There are probably other local components that have a factor there, but that's the general situation that the higher the elevation, the closer to precipitation sources, with significant percents of their total area in the upper parts rather than in the lower parts of their regions.
Audience 1: You mentioned earlier in the talk the importance of glaciers as a freshwater source for not just ecosystems but humans. Are there examples in the United States where humans are using, people, society is using glaciers as a primary water source today?
Bruce Molnia: The best example is in the Boulder, Colorado area where Arapaho Glacier had been the primary source of water for the community of Boulder. Obviously, as Boulder has grown, the Arapahos run off just as incapable of supporting the larger population. It still is a component, though, of the water supply.
You get further north into Wyoming, Montana, a number of the rivers that are running from the higher mountains are sources of water both for irrigation and for human use in many of the communities along the banks of the rivers.
You go other continents, though, and glacier runoff is far more important. In the United States, we have so many other sources, but in the Himalayas, glacier runoff probably is responsible for a third to half of the total potable water.
And as the glaciers are decreasing, there are long-term and short-term concerns about what will happen as population continues to grow. There was a National Intelligence Assessment done last year that suggested that melting in the Himalayan glaciers may be one of the geopolitical factors that leads to global conflict.
Any other questions? Again, thank you very much.