PERMAFROST MELTING WITH GOOGLE EARTH:
RETROGRESSIVE PERMAFROST IN THE YUKON AND NORTHWEST TERRITORIES
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" (Google Earth BBS link). Some of the sites like the near the Bonnet Plume River have some excellent
high resolution digital camera image overlays.
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
(See the National Air Photo Library on-line site).
I have taken a few if the sites and analyzed the information below from a time
SITE 3: Bonnet Plume, Yukon Territories, Canada (KML link)
This site is within the Peel River Plateau Ecoregion
and the Taiga Plain Ecozone. The landscape is almost entirely shaped
as result of the Laurentide glaciation, and post glacial fluvial
and other geomorphological processes. Continuous permafrost is present
with depth to base of ice-bearing permafrost close to 300m (Geological
Survey of Canada, unpublished data). Retrogressive thaw flow slides
are common where ground ice has been exposed in glaciolacustrine
deposits by forest fires, debris flows and regressive erosion. (Ecoregions of the Yukon: Peel River Plateau).
Figure 1: This Google Earth oblique image shows a permafrost slide near the
Bonnet Plume River. The slide is significant in size. The active melting edge is about 2700 meters
in length. The maximum regression distance is 1250 meters.
The slide shows continuing erosion and melting and as the
air photo sequence below indicates started well before 1949.
The high resolution GE image shows a recent forest fire (dark
grey green) on top of the plateau. The steeper escarpment facing
this way, was not
burned except around
Figure 2: 1949 air photo shows that a significant slide occurred before 1949 (outlined in blue). The
dotted lines identify other active slide areas. It would suggest
that significant sliding started between 1935 and 1945. Wildland
fire history records are available for this areas since 1946.
According to these records,the first major fire occurred between
Considering the large amount of sliding before
1949, one can speculate the a significant fire occurred during
that period possible associated with an above average warm summer.
Figure 3: 1953 Air Photo
The slide areas appears to have stabilized in this image. The major slide area
(right) is still active, but the small ones are covered by
Figure 4: 1968 Air Photo
The major slide area in 1968. The red line outlines the slide, the dotted lines
show some smaller active slide areas on the escarpment which
have stabilized by 1994 and show no further sliding. Between
1949 and 1968 the melting rate showed a maximum of 12.7 meters
per year and a median rate of 7.8 m/y. The smallest regression
rate in this period was about 4.5 m/y
Figure 5 1994 Air Photo
The yellow dotted line shows the melting edge in 2007. Between 1994 and 2007
the melting- permafrost regression rate varies from a maximum
of 17.5 meters per year to an average of about 10 m/py to
a minimum of less than 1 m/py.
Melting rates between 1963 and 1994 are as follows: Maximum rate was 8 m/y: median
4.4 m/y and minimum 2.4m/y.
Figure 6: 2007 Google Earth image with permafrost melting stages between 1949
The maximum rate of melting over this 58 year period averaged out to 9.2 meters
per year. The lowest rate to about 5.1 m/y. The median about
6.8 m/y. The melting rate measured was the fastest during the
last 14 years (maximum rate 17.5 my; median 11.5 m/y; minimum
The thin light dotted line separates the area burned between 2000-and 2004 (see
fire history map below)
||Figure 6 NASA 1990 Landsat Pseudo Colour image. This 1990 image provides some
indication of the fire history. The white square represents approximately
the area covered by the air photos above. The slide itself shows
as purple, devoid of vegetation and moist.
||Figure 7. 2000 Landsat image shows that the slide has increased, but also that
the vegetation cover types are essentially the same in 1990 and
2000: no forest fires have occurred.
||Figure 8 Fire History: The study area was burned between 2000 and 2004 according to the map to the left.
||Figure 9: Topographic Map Detail for the permafrost slide area highlighted by
the red oval.
Figure 9: Segment of the Canada Geological Survey Map of Canada: number 1880A- Surficial Materials of Canada
This map was compiled by my former colleague
and friend R.J. Fulton, 1995