Geology Reference
In-Depth Information
Table 7.2 .
Typical ground-ice volumes, Arctic Canada. (A) In the upper 5 m of permafrost in
tundra lowlands of the western Arctic. (B) In the upper 7 m of permafrost on the Fosheim
Peninsula, Ellesmere Island.
A. Upper 5.0 m of permafrost, unconsolidated sediments, Western Arctic
Pore/Segregated ice (%)
Wedge Ice (%)
Total ice (%)
King Point, Yukon
43 (79)
11 (21)
44 (100)
Richards Island, NWT
28 (79)
7 (21)
36 (100)
Southwest Banks
44 (77)
21 (37)
56 (100)
Island, NWT
B. Upper 7.0 m of permafrost, bedrock, Fosheim Peninsula, Ellemere Island, Nunavut
Vol of ice (km
3
)
Ice Content (%)
Total ice (%)
Massive ice
0.179
69.0
6.8
Pore/segregated ice
1.970
48.6
74.5
Bedrock
0.407
9.7
15.4
Wedge ice
High density
0.028
3.5
1.0
Low density
0.060
1.8
2.3
Note: Values in parentheses in (A) indicate percentage contribution of ground ice to total ice
volume. In (B), ice content (%) is that of ice volume (km
3
) and total ice (%) is the percentage of
total ice volume by ice type.
Sources: Harry et al. (1985), Pollard and French (1980), French and Harry (1983), Couture and
Pollard, (1998).
lowland localities in the Western Canadian Arctic. The total volumetric ice content
varies between 35% and 60%, of which the majority (66-80%) is either segregated or
pore ice. Similar conclusions were reached by J. Brown (1967) for the northern Alaskan
Coastal Plain. Clearly, in regions such as these, ground ice is an important component
of permafrost.
Even where extensive natural exposures of permafrost are present, or where detailed
borehole data are available, most estimates of ground ice volume in the upper 1-10 m of
permafrost are gross approximations. The problem is one of generalizing from a relatively
small number of observation points, often with an irregular spatial distribution, to the
landscape at large. Bearing this in mind, several attempts have been made to characterize
ground-ice volumes in near-surface permafrost. For example, using information from
man-made trenches and large excavations (sumps) associated with the drilling of explora-
tory boreholes on Melville Island, H. M. French et al. (1986) concluded that mean values
of ice volume ranged between 30% and 70% in the upper 7.0 m. Similarly, on the un-
dulating terrain of the Fosheim Peninsula of Ellesmere Island, the mean ice content of
154 cores drilled to 1.5 m depth was 53% (Hodgson and Nixon, 1998), but with additional
observations upon massive ground ice exposures and soil moisture measurements at
53 sites, a slightly lower value of 48% for the upper 7.0 m of permafrost was subsequently
obtained (Couture and Pollard, 1998; see Table 7.2B).
Little information is available about total ground ice amounts in igneous and meta-
sedimentary rocks. However, it seems reasonable to assume that ice volumes are low and
vary from 1-2% to 10-15%.
