| jean_thie |
| (Cartographer) |
| 12/17/06 08:58 PM |
| View in Google Earth |
Global warming melts permafrost
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www.geostrategis.com/p_mapm2.html
www.ecoinformatics.info
Google Earth and Climate Change: Google Earth provides a fascinating way to explore the earth remote ecosystems.
Few people would imagine that GE has the resolution and detail to monitor ecosystems, but an experienced interpreter can do remarkable
things with Google Earth.
A 2005 Google Earth visit to one of my old research sites in Manitoba, Canada, showed that Google Earth can be used to approximate the melting rates of permafrost in peat landforms. These two combined inages show a comparison of permafrost in peatplateaus just north of Lake Winnipeg. This area is within the so called southern sporadic permafrost zone, but because of its unique wetland situation permafrost is quite widespread (see for example E in 1926) and visible. Even the low resolution Google Earth images shows the melting edge clearly. The two major peat islands are aslo shown on the second image below as B and C.
The compsite figure below shows a combination of a1926 oblique aerial photo, a 1947 vertical air photo projected as oblique and a 2005 oblique Google Earth image. The permafrost around A is still present in 1947 but totally melted in 2004. The peat plateau B shows some melting (collapse holes) inside the plateau in 1947; but in 2005 they joined together and are forming a peripheral collapse. Area C is interesting because it was burned before 1926 regenerated a black spruce cover and shows still its frozen state in 2005. In fact the melting process in B and C seems very comparable. So fire does not necessarily increase the rate of permafrost melting. On the other hand, the the small peatplateau at touching the top of (A) melted within years after a fire in the late 60's.
A close up view from helicopter: Black Spruce (Picea mariana) grow on the frozen core in the middle. They are about 12-15 meters in height. The collapsing edge shows surface water and leaning trees and trunks sinking in the non-frozen wetlands. Tamarack (Larix Laricina) growth is denser around the original edge of the palsa.
Extensive collapse scars of former peat plateaus. Very little permafrost is left except for areas near (2). This area was burned a number of years ago. In these small areas of permafrost white birch and black spruce regeneration is seen. The relative recent collapse areas are marked with (1), older scar areas with (3)
Analysis page comparing 1929 and 1947 aerial photographs, and 2005 Google image and field work photos available at http://www.geostrategis.com/p_mapm2.html
website: www@geostrategis.com
| jean_thie |
| (Cartographer) |
| 01/02/07 09:56 AM |
| View in Google Earth |
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Re: Peatland Sensitivity to Climate Warming Map
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This Peatland Sensitivity Map to Climate Warming was prepared by Kettles and Tarnocai (1999) and superimposed on Google Earth Satellite image. It covers the exaple of permafrost melting in the previous post. It shows that this area is considered extremely sensitive to climate warming.
. It is displayed as overlay in Google Earth for Manioba and a portion on Ontario in Canada.
In this area the southern permafrost line would move about 300 kms North.
Permafrost Sensitivity Map
In Canada peatlands cover about 12% of the land surface. (over 1.13 million km2). A large part of the carbon stored in peatlands could be released in the atmosphere as carbon dioxide and methane, further increasing climate warming.
More Information at: http://www.geostrategis.com/p_sensitivity.htm
http://www.geostrategis.com/p_mapm2.html
| heamit |
| (Master Cartographer) |
| 01/02/07 04:57 PM |
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Re: Peatland Sensitivity to Climate Warming Map
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Hi jeanthie and welcome to Google Earth!
These are great - thank you for posting them!
| jean_thie |
| (Cartographer) |
| 01/03/07 09:22 AM |
| View in Google Earth |
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Re: Peatland Sensitivity to Climate Warming Map
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Dear Heamit,
Thanks for your supportive comments. It is kind of nice to get back to use Google Earth to get back to my deep past. I used to be the first Head of Applications Development Division of the Canada Centre for Remote Sensing (1973-1975). Interpretation and analysis (visual or automated) of satellite and airborne images have always fascinated me, and GE allows me to play with this again. Of course I have done this stuff with ERTS and LANDSat imagery in those days, but now it is accessible to almost everyone!
By the way, the interesting part of this permafrost is that it is at the most southern edge of its occurrance. This is by no means the Arctic, but the Mid Boreal zone. While melting rates have been reasonably consistent in the last 50 years, you could expect significant more change in the next 20 years. Also surprising is that the permafrost occurs in some areas within 50 meters of the shoreline. See image below
for more information
www.geostrategis.com/p_mapm2.html
www.ecoinformatics.info
| Hill |
| (Master Guide) |
| 01/03/07 02:11 PM |
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Re: Global warming melts permafrost
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Quote:
Few people would imagine that GE has the resolution and detail to monitor ecosystems, but an experienced interpreter can do remarkable
things with Google Earth.
I think you will find that GE is used more and more for scientific research and documentation as more scientists find just how useful it is. The link to the website is very useful also. Thanks for your post.
| jean_thie |
| (Cartographer) |
| 01/04/07 06:05 PM |
| View in Google Earth |
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Re: Reconstruct "the past" with Google Earth
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Quote:
I think you will find that GE is used more and more for scientific research and documentation as more scientists find just how useful it is.
Dear Hill, Thanks for your comments and I completely agree with you. Scientist will embrace it, initially to visualize and communitcate their knowledge and later to influence societal decision making. For me, Google is already the main knowledge access tool I use in my daily work. When Google Earth and other geospatial tools are fully integrated with it, we will have a real knowledge management service, especially for the geo-sciences: a sytems which allows integration, analysis, modeling etc. If we integrate the global geospatial data infratructure initiatives with GE, we can rapidly move to a societal geospatial knowledge infratructure.
By the way, I found GE particularly useful for reconstructing and comparison with the earliest oblique aerial photography available.(taken often before the 1930’s from fixed wing aircraft)
This is an example I used for permafrost comparision between 1926 and 2005.
for more information see also
http://www.geostrategis.com/p_mapm2.html.
and
http://www.geostrategis.com/p_sensitivity.htm
home base
http://www.geostrategis.com
| jean_thie |
| (Cartographer) |
| 01/16/07 12:31 PM |
| View in Google Earth |
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Re: Impact of Forest Fires on Permafrost
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Impact of Forest Fires on Melting of Permafrost in Peatlands.
The GE image below shows This is an example of a 1930 fire which burned part of a large peatplateau complex. After the burn black spruce regenerated naturally and no increased melting was observed in 1974. Even in 2004 this Google Earth image shows that permafrost still exists with a similar distribution as in the non burned area. Melting has continued at a steady pace.. Fire records in this area do not show significant fires in the last 15 years. A few very small areas can be found (see recent small burn), bit the immediate impact of those cannot be assessed. GE resolution is not adequate for that in this area. Although fire generally did not have an impact of acceleration of melting rates, one particular small peatplateau totally collapsed after a burn in 1965.
This picture below was taken 1970 from helicopter. It shows the area burned in previous image. The area B was not burned in 1930, the area A is also a part of a stand which survived the fire. The regeneration is primarily Black Spruce, with an occasional bright dots of White Birch. The light colored collapse areas around the edge and in the centre are quite distinct.
Typical fire regeneration on permafrost peatplateaus in this area, trees are 30-40 years old. The peat auger in this picture is in the permafrost which starts at about 50 cm or 2 ft below the surface. (late August).
Website: www@geostrategis.com
More information
http://www.geostrategis.com/p_mapm2.html
| jean_thie |
| (Cartographer) |
| 03/02/07 02:24 PM |
| View in Google Earth |
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Re: Global warming melts permafrost
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Palsa near Cranberry Portage, Manitoba.
This image gives a good cross section of the permafrost development in the peat and clay layer. The fieldwork for this diagram was carried out between 1968-1970 by two of my forest ecologist friends Steve Zoltai and Charles Tarnocai.
This cross section is very indicative of the situation described in the first post on permafrost melting just north of Lake Winnipeg. The glacial lake Agassiz clays form the mineral layer, which is covered by up to two meters of organic material. Permafrost extends into the clay layer. Onviously the premafrost was developed after the galcial lake retreated and the organic layer formed. It is actually the result of a very intricate interaction of climate, microclimate and forest cover and insulating properties of sphagnum mosses.
More information at
http://www.geostrategis.com/p_mapm2.html
and
www.ecoinformatics.com
| gideonshorn |
| (Tourist) |
| 03/21/07 02:11 PM |
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Re: Global warming melts permafrost
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Jeanthie,
Thanks for the great post. You have done some wonderful work.
Rick Marshall
| jean_thie |
| (Cartographer) |
| 08/13/07 10:00 AM |
| View in Google Earth |
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Permafrost Melting North of Lake Winnipeg
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This folder contains a series of aerial photos taken between 1926
( aerial obliques) , 1946, 1967, 1971 which provide a source of comparison for studying the melting of permafrost in the form of palsas and peatplateaus at the most southern limits of occurance.
For more information: www.geostrategis.com and
http://www.geostrategis.com/p_mapm2.html
Site A:
Collapsing of permafrost is regularly distribute over the area. The red areas show the location of permfrost melting between 1947 and and 1957. Most of the area was burned in 1930 (except the darker treed- black spruce islands (on permfrost), but there are no signs that the burn accelerated melting rates. For example some of these darker 'black spuce on permafrost islands' have almost completely melted away between 1967 and 2000+, the date of the GE image. use the transparency slider to compare the two dates. Maximum extent of the permafrost in this area is likely correlated with the 'little ice age'. Just outside the overlay about 1.3 km north west of the left top corner is a small area burned about 3 years before the date of the GE image.
Site B: This area is interesting because most of the permafrost has diappeared. The small dark tread areas of black spruce on permanently frozen peat plateaus were all that was left of the once extensive permafrost. At its maximum extent about 65% of this site had permfrost. In this area most of the melting actually occured before 1946. In 1967 only the small dark spots remained. They tend to occur on the edges of the former peat plateaus. Most of these have disappeared now or are significantly smaller. Barely 1% of this site still has permafrost.Aerial Photo 1967; Red marks show areas melted between 1946 and 1967. Fieldwork carried out in 1973.
Site C:This photograph was taken as part of a multi-sensor aerial flight over the study area by the Canada Centre for Remote Sensing Airborne Division for the Manitob Remote Sensing Program. The colour photo was taken towards the end of the growing season. This site is remarkable because many of the small permafrost island still exist today and show relative small rates of melting.
Site D: Significant melting occured here before 1926 and this 1926 oblique photo gives an excellent image of the collapse scars which remain after the melting of the permafrost. Melting has continued since 1926, but permafrost remains are still visible on the GE image
Approximatearea coverd by the oblique aerial photo.
Site E:
This photo compared with the underlying Google Earth image provides a 60 year time frame to study the melting of permafrost. The permafrost in the form of Black Spruce forested peat plateaus and palsas is delineated on the photo after filedwork in this area in 1969-1971. Most of the smaller bodies of permafrost have disappeared and the larger ones show slow but steady melting around the perimeter.
| kingpointnorth |
| (Tourist) |
| 11/02/07 10:31 AM |
| View in Google Earth |
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Re: Global warming melts permafrost
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The attached kmz file may be of interest to this discussion as well. Here I have used Google Earth to doucment observed or suspect permafrost failures in the North Yukon and Western NWT.
| jean_thie |
| (Cartographer) |
| 01/25/08 08:58 PM |
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Re: Global warming melts permafrost
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Hi, Kingpointnorth,
This is an exceptional selection of permafrost failures/ regressive thaw phenomena. Some of them are as impressive as the melting of glaciers. Did you find these permafrost failures with Google Earth or did you just use GE to map them? Of course they are part of the natural dynamics of permanently frozen sloping or eroding landscapes and it would be interesting to know if the regression has accelerating in the last 30-40 years. Do you have an answer?
I am studying a few of your sites on various satellite imagery and older aerial photographs. Do you have more information on your Red Marked site?
| jean_thie |
| (Cartographer) |
| 02/03/08 06:08 PM |
| View in Google Earth |
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Permafrost melting: A glacier like retreat
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EXPLORING PERMAFROST MELTING WITH GOOGLE EARTH:
RETROGRESSIVE PERMAFROST THAW IN THE TREVOR RANGE YUKON
An excellent selection of sites in the Yukon showing significant slides and regression of permafrost in mineral soils was made available on Google Earth by "kingpointnorth"
In the context of climate warming, it is interesting to look at some of these sites over a period of 50 years or more. Aerial photography has been taken in the North since the mid 1920's. From the 1950's on aerial photography becomes a more dependable source of information for comparison.
Figure 1 below shows a glacier like retreat of land based permafrost. It is based on a comparison and interpretation of a series of aerial and satellite images. The left is an 1966 July Aerial photo (A19650-67) draped over a Google Earth. To the right is the Google Earth high resolution Digital Globe July 2004 image. The grey dotted lines show the permafrost melting/ erosion edge in 1966. The Yellow dotted line is derived from a NASA Landsat 1990 low resolution image interpretation (WorldWind) and the orange dotted line is represents the GE 2004 digital Globe image.
The maximum regression distance over the 38 year period is about 850 meters, while the active edge is close to 890 meters in length. Average regression rate would be in the order of 20 meters per year . Most of it, certainly volume wise, in the last 14 years. There ar no indications that this slide has been triggered by wildland fires as there is no evidence of fire history on the aerial and satellite images.
This melting and regression rate is comparable to other rates documented in the Yukon. Form example Burn and Friele (1989 Arctic vol. 42 no.1, p31-40) measure regression rates of up to 16 meters per year in retrogressive thaw slumps near Mayo, Yukon Territory
more information at: http://www.geostrategis.com/p_permafrost-slides.htm
| kingpointnorth |
| (Tourist) |
| 02/06/08 10:22 PM |
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Re: Global warming melts permafrost
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Hi Jean,
Thankyou for your response and interest. Nearly all of the failures were identified using Google Earth. Many are suspect due to the low resolution coverage over most of the Yukon. Those that fall within the high resolution coverage areas are easily identifiable and in some areas numerous. As the high resoultion coverage improves I keep adding more sites. The numbers are significant indeed.
I have had the opportunity to fly across the Peel Plateau on several occasions. In 2005 we did pass by the larger site marked in red; at the time I was able to photograph this and a few other failures along our flight path. I understand that others have as well but to what extent I am not sure.
After inspecting the red marker site from the air, photographing it and then later looking to see if I could pick it out on Google Earth (sometime later in 2005 or early 2006), it did not take long to find more features that had the same or similar characteristics - a few dozen to start with. At that time it was all low resolution coverage but with the newer high resolution coverage the total number is now in the hundreds (I have lost count). Some are in the range of 1km in length. I continue to look and add to my list as time permits.
I can send you the photographs of those that I have flown over if you like. I have not been on the ground so can't offer any more details or measurements.
The red marker site does show that the failure has gone through a transistion from being active and then partially stablizing. It appears to me it most likely created the small lake immediately upstream. I have looked at WorldWind and found this site but the resolution is such I think it would be hard to meaure change over time. The use of aerial photos from the past 40 to 50 years is probably the only way to do this comparison (such as what you have done so well) . I have no idea if the rate of change has accellerated or not.
I have discussed this briefly with Panya Lipovsky her with the Yukon Government but I don't know if she has had a chance to look at this in more detail.
I will sign off for now. Please stay in touch. Let me know if I can send you the photos.
Cheers,
Doug Davidge (kingpointnorth)
| jean_thie |
| (Cartographer) |
| 02/18/08 09:29 AM |
| View in Google Earth |
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Permafrost melting: Retrogressive Thaw, Yukon
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Hi Doug,
Your selection of permafrost slide markers is really very interesting. Each of these sites warrants further studies. Your photograps would certainly be of interest. Why not add them to this discussion thread.
Your red marked site is very interesting since it shows very recent as well as 50 year old slide scar areas. The relative recent disturbed bare soil is clearly visible on both sides of the creek. Also the adjacent areas on both sides show significant sliding area which appear to have been stabilized and are recovered with vegetation.
I have taken some time to study your red marked site in more detail using air photos from 1950, 1953, 1972 and 1977, as well as Landsat. the image below shows my interpretation . You are right that the pre 1950 slide caused the formation of the little lake upstream. The pre 1950 slide appears to have been a sudden event. The pink arrow shows the slide path, which also blocked the creek flow, and created a small lake upstream. The the water erosion from the displaced creek started to undermine the north facing slope which showed a steady regression for the next 27 years before stabilizing. Just before the 1990's additional regression occurred on the south facing slope (thin orange line) also occurring as a sudden failure. The new slide areas (yellow dotted line) developed between 1990 and 2000.
Retrogressive Slide on 1950 and 1953 Aerial Photos
The 1950 photo ( A12847-144) was taken on August 2nd, 1950 at a height of 20'000 ft. Original scale 1:40'000. The pink arrow shows the flow direction. The slide, on the south facing slope occurred as a sudden event blocking the flow of the creek and creating a small lake upstream. The drainage channel was pushed into the opposite slope which started to collapse. Both sides continued to melt, but most of the regression in the following decade is in the north facing slope. The 1953 airphoto (A13753-22) was taken on 27 July from 35'000 ft.
1972 and 1977 Air photos
During the next 20 years the North facing slide is regressing. The 1972 and 1977 air photos show that the creek is pushed back again (yellow marker). In this 5 year period the North slide appears stable, and some further sliding occurred on the south facing slide (from blue dotted line to the light blue-grey dotted line). There are no signs of fire scars in the vegetation on these photos, but a fire scars ( (dated between 1958-1978) were identified in close to the Salter Hill area, about 5 km distance from this slide area. 1972 Airphoto (A22972-119) taken on 11 July, from 35'000 ft; 1977 air photo (A24761-133) taken on August 1, from 35'000 ft.
NASA Landsat Pseudo Colour 1990 (left) and 2000 (right). The pink arrow on the 1990 satellite image shows that the south facing slope has become active again. Also the light blue arrow shows the start of the next phase on the north slope. The 1950 and 1970 slide areas still look reasonably stable and are covered with vegetation again. The red arrow on the 2000 image shows a part of the 1950 slide which has become active again: the small dark black area- a mudflow The yellow arrow on the 2000 image points to the dark purple active slide area essentially very similar to the Google Earth image (2007). No fire scars are visible on each of the images.
Fire History for the Yukon 1946-2004 . The map below depicts the wildland fires since 1946. Source: Source: Yukon Energy, Mines and Resources . The Caribou River area described here is marked with the red marker near (1). The closest fires on this map was (3) which occurred between 1990 and 1999. The Trevor Range Site (green marker) is identified with a (2). It will be interesting to study the blue markers provided by kningpointnorth in relation to fire history. A cursory review of some of the sites in recent and older burn areas seems to imply a link with the fires. Legend: Grey= 2000-2004; Red=1990-1999: Pink=1980-1989; Green= 1970-1979; Orange= 1960-1969; Yellow=1950-1959; Light Green= 1946-1949 (not on this part of the map)
Doug, you could add the fire map as overlay to your collection of markers. As you already can see, many of your markers are in burned and non-burned areas. I have looked at a number of the sites in recent burn areas, where the fires appear to be the cause of the slide. Fires can also have an impact on increased stream flow and therefore increased erosion.
Fires are already so abundant in this part of the world. If they double in frequency as result of climate warming, retrogresive thaw slides would certainly become more abundant. It would be interesting to study this with your markers and the existing fire history,
It is so far my impression from your markers and these preliminary analysis that ther could be twice as many slides today than there were 60 years ago.
Cheers,
Jean
| sateliteoflove |
| (Tourist) |
| 03/06/08 05:45 AM |
| View in Google Earth |
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Re: Global warming melts permafrost
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Hi, Jean Thie and others,
Am I right to assume that there is no way to prove permafrost melting occurs other than bij comparisson to earlier aerial photgraphs?
I am not a scientist, rather an artist who wants to convey the feeling of urgency of global warming issues using Google Earth as a source of inspiration (check my weblog http://googleearthart.blogspot.com )
The first painting I made in this Google Earth series was of a part of the Russian Tundra. I found a strong image I could use as inspiration, but I have no idea if there is any evidence of permafrost melting on that location. Are there maybe teltale signs (like a large number of small lakes which could all go anaerobic)? If I'm to make a statement of some sorts with my paintings, I would should at least know a little bit of what I'm talking about.....
I've included the KMZ file of the location. The painting is on my weblog.
I'd be gratefull for any wise words on the issue.
Keep up the good work!
Evert Schut
| jean_thie |
| (Cartographer) |
| 03/13/08 02:45 PM |
| View in Google Earth |
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Siberian Permafrost Thaw Lakes and Lanscape Art
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Beste Evert,
You pose some interesting questions about permafrost melting. Using Google Earth as an artisitic source of inspiration is a great approach. Permafrost landscapes provide particularly fascinating landscapes often reminiscent of modern art and no better way to see these than with satellite or airphoto images.
To answer your questions:
1) Satellite and air photos provide especially effective tools to study environmental change over time. Field work, sample sites, data collection and monitoring are critical components of satellite based landscape studies. There are global monitoring networks have reasonably long records of permafrost monitoring (active layer dynamics, ground temperature, permafrost depth etc.). The Global Terrestrial Network for Permafrost is an example: http://www.gtnp.org/index_e.html. A good practical example is the East Siberian and Alaskan Transect Project: http://www.gi.alaska.edu/snowice/Permafrost-lab/projects/projects_completed/proj_transects.html
2) The image of the Siberian Tundra you used shows a typical permafrost wetland landscape. It is in the continuous permafrost zone and it does not show any dramatic melting, but it demonstrates typical arctic lake permafrost dynamics. In fact a number of lakes have disappeared over time and within the dried up lake bottoms permafrost is building again.
3) To understand the relationship between permafrost melting and climate change, you have to understand that the building of permafrost (aggradation) and the melting of permafrost (degradation) are two processes that occur more or less simultaneous. The active layer of soil which freezes in winter and thaws in summer is an example of this. The figure below demonstrates the varying thickness of the active layer and the aggrading permafrost which is filling in a former lake again. ( source: http://piru.alexandria.ucsb.edu/collections/geosystems/geosystems17-17.jpg
4) Your blog talks about methane and the BBC series. It is interesting to note that one of the research sites is quite close to your “painting”. I have inserted below one of the illustrations and provided a link to the location on GE. This study talks about the melting of Yedoma , a Pleistocene loess permafrost with a high ice content and rich in organic matter. Source: http://www.nature.com/nature/journal/v443/n7107/abs/nature05040.html
The landscape studied here is different from your area; in particular fewer thaw lakes and more sloping terrain. If you study this area in detail you can also see the rich fire history. Wildland fires occur frequently and are expected to increase significantly due to global warming.
5) For comparison I have included an image from Barrow Alaska showing the age of thaw lakes in ice rich permafrost. The source: http://www.geography.uc.edu/~kenhinke/dtlb/
Gegroet
| sateliteoflove |
| (Tourist) |
| 03/14/08 02:08 PM |
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Re: Siberian Permafrost Thaw Lakes and Lanscape Art
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Dear Jean,
Thanks a lot for your extensive reply! I just read through quickly and it looks like I will have to do quite a lot of further reading before I can say anything about permafrost melting with even the slightest authority.... Lucky for me an artist can get away with an 'artists impression', but I feel it's my obligation to at least know a bit more about what's really going on. I hope you will bear with me and my lay questions.
From your reply I understand that the thaw lakes are quite natural in a wetland permafrost environment. The BBC documentary gave me the impression that the (anaerobic) conditions in the lakes cause methane production, so is this also a natural process? So are scientists worried about an increased rate of methane emissions as result of increased melting of permafrost (leading to more and bigger permafrost lakes)? Or is the methane production in this area itself something new? Or perhaps the production of methane is not restricted to deep lakes?
Have any esimates been made of the total increase in methane emissions in artic zones? I think I read somewhere that the IPPC models have not yet taken this into account. Is that right?
Between the lines of your reply and other posts I get the impression that increased fire damage is at least as big an issue as methane emissions. I know, reading between the lines is risky business. Perhaps you can put me straight?
Thanks again for your efforts! Cheers
Evert.
| kingpointnorth |
| (Tourist) |
| 03/25/08 10:21 AM |
| View in Google Earth |
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Re: Permafrost melting: Retrogressive Thaw, Yukon
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I will upload individual photos of a few of the permafrost failures I was able to photograph from a helicopter in 2006 using a 10 megapixel camera. This site is located on the Bonnett Plume River just upstream of it's confluence with the Peel River. The low angle of the photo does not allow for a good overlay on GE but you will be able to see a great deal of ground level detail. Cheers....
| kingpointnorth |
| (Tourist) |
| 03/25/08 11:00 AM |
| View in Google Earth |
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Re: Permafrost melting: Retrogressive Thaw, Yukon
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This is the 2nd oblique photo upload to this discussion showing a permaforst failure in the upper Eagle River watershed. This site is located about 16 km east of the Eagle Plains Lodge along the Dempster Highway. The photo was taken from a helicopter using a 10 megapixel camera.
Cheers
Lrae
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| (Master Wizard) |
| 03/25/08 12:30 PM |
| View in Google Earth |
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Re: Permafrost melting: Retrogressive Thaw, Yukon
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Kingpoint,
Just thought you might like to try another way of displaying your images.
Photo Overlay. Zoom into the image.
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Lrae
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| (Master Wizard) |
| 03/25/08 12:38 PM |
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Re: Permafrost melting: Retrogressive Thaw, Yukon
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This KMZ doesn't seem to work.
| kingpointnorth |
| (Tourist) |
| 04/02/08 01:42 PM |
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Re: Permafrost melting: Retrogressive Thaw, Yukon
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Hi Lrae,
That is exactly what I needed/wanted to do. Thanks for showing me. I am new to the practice of adding overlays to GE so your help is very much appreciated. Many thanks!!
Kingpoint
| jean_thie |
| (Cartographer) |
| 04/06/08 06:19 PM |
| View in Google Earth |
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Re: Permafrost melting: Retrogressive Thaw, Yukon
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Hi Kingpoint. Your picture of the Bonnet Plume River permafrsot slide is really excellent and provides a good indication of active slide areas as well as vegetation cover. The area was burned between 2000 and 2004 according to fire history records.
I looked again at some old photographs from the national Air Photo Library collection in Ottawa. Below are some examples. The coverage started in 1949, 1953, 1968, 1994. The slide started already before 1949. Much earlier than I exected. In fact the photos of 1949 showed a significant amount of thaw features which since have stabilized. A number continued to grow as this one. The average melting rate between 1949 and 2007 is about 7 meters per year. The last 14 years the rate appears to be on the average about 11 meters per year.
I will do some more work on this, but in the meantime here is the overview image. Your aerial photo provides an excellent reference for interpreation.
More information can be found at my website: http://www.geostrategis.com/g_permafrostslide-bonnet.htm
