Geology Reference
In-Depth Information
Figure 15.2.
Temp erat u reprofi les measured in 1985, 1998, and 2004 in the hole at Barter Island
near the village of Kaktovik, Alaskan North Slope. From Osterkamp and Jorgenson (2006). Repro-
duced by permission of John Wiley & Sons Ltd.
lakes of half-width 130 m. By using a taiga lake near Inuvik (i.e. south of treeline and in
a warmer climatic environment) as an analog for the potentially-warmer summer tempera-
tures and higher winter snowfall, it was inferred that the critical size and half-width of
round and oval lakes that would be required to penetrate permafrost would decrease to
165 m and 80 m, respectively. This would mean that about 20% of the Pleistocene delta
would eventually be underlain by unfrozen ground.
In all these scenarios, it must be emphasized that degradation would be gradual and
restoration of a new ground thermal equilibrium might take several millennia. Associated
with these changes would be enhanced regional thermokarst activity. As described in
Chapter 8, a range of processes would be involved, including subsidence, erosion, increased
run-off, and slope instability.
15.2.4. Changes in Cryogenic Processes
Climate warming will also affect the magnitude and frequency of many of the geomor-
phic processes currently operating in periglacial environments. Current monitoring of
thermal-contraction cracking, thaw-slumping, and active-layer detachments suggest that
change is already occurring. For example, information on the frequency of current
thermal-contraction cracking is now available from the Western Arctic Canada, northern
Quebec, and Svalbard (see pp. 123-127). Continued monitoring should detect any
ongoing climatic change. It is also possible to infer past climate change in the Western
