Permafrost

154
Frost Penetration Beneath Snow Cover
Saarelainen Seppot
(Technical Research Centre of Finland VTT, Materials and Building, P.O.B. 1000, FIN-02044 VTT,
Finland, tel. +358 20722 4895, email: seppo.saarelainen@vtt.fi)
Abstract: In civil engineering, frost penetration is normally estimated for a snow-free ground
or pavement. In a natural terrain a layer of snow decreases strongly cooling, and thus also frost
penetration. In seasonal freezing and thawing, the length of thaw depends on the frost
penetration during the previous winter. Thus, the snow cover dramatically reduces the length of
thaw-weakening period.
In this study, frost penetration in a ground covered with a layer of snow is studied. The
approaches include modeling of frost penetration in a ground, and air temperatures are varied in
the course of time. The snow cover can be given as constant or varying with time. Some
examples are presented, verifying the approach.
Key words: frost penetration, modeling, snow cover
The Effect of Ad Hoc Management on Alaska’s North Slope
Winter Oil Exploration Season
Sherri L. Wall
(University of Alaska Fairbanks)
Abstract: Over the last 30 years, the length of the winter tundra travel season allowing oil
exploration on Alaska’s North Slope has declined from 200 days in the early 1970’s to 100
days in 2003. The narrowing operating window, attributed to climate change, poses a threat to
the fiscal stability of the State of Alaska and the energy security of the United States. The
implications to Alaska’s economy from declining oil revenues are profound since oil royalties
and taxes account for 84 percent of the State’s general fund revenues. Furthermore, with 19
percent of U.S. production, Alaska’s oil reduces the nation’s dependency on unstable foreign oil
sources. The shortened season has been prolifically cited as an indicator of climate change in
publications, climate change conferences, and news media.
The Department of Natural Resources (DNR) has responsibility for making the yearly
determination of when tundra conditions are suitable to declare a “general opening” for winter
exploration. DNR has roughly followed a heuristic “12 & 6” standard which requires 12
inches of frost to be present in the active layer and 6 inches of snow coverage for vegetation
protection. The standard was incorporated into the environmental impact statement (EIS)
prepared in 1975 for the Navy’s exploration of what is now the National Petroleum Reserve of
Alaska (NPR-A). The objective of this research was to review DNR’s management history
in conjunction with statistical analysis of available scientific data to determine how much of the
declining season can be attributed to climate change as compared to management choice. The
results suggest that ad hoc management has been responsible for 85% of Alaska’s shortened oil
exploration season.