active-layer

Other approaches can also be used to calculate active-layer thickness (e.g., using a full surface energy balance).

Infrastructure and climate in the Arctic 2009

An increase in ground temperature along an existing pile is very likely to reduce its bearing capacity or increase the rate of its settlement for two reasons: an increase in the active-layer thickness will reduce the effective embedment length of the pile; and increased temperature will reduce the strength of the frozen soil.

Infrastructure and climate in the Arctic 2009

The susceptibility of permafrost to environmental hazards associated with thermokarst, ground settlement, and several other destructive cryogenic processes can be crudely evaluated using the geocryological hazard index, which is the combination of the projected percentage change in active-layer thickness and the ground ice content:

Infrastructure and climate in the Arctic 2009

The air thawing index can be used to calculate active-layer thickness and maximum permafrost temperatures as a function of depth and time of year (see section 16.2.2.2).

Infrastructure and climate in the Arctic 2009

Eqn. 16.2 where Δzal is the percentage increase in active-layer thickness, and Vice is the volumetric proportion of nearsurface soil occupied by ground ice.

Infrastructure and climate in the Arctic 2009

In areas with significant topographic variations, flowing water can carry heat into drainage channels, causing increased soil temperatures and increased active-layer thickness [52].

Effects of climate change on landscape and regional processes and feedbacks to the climate system in the Arctic 2009

Increases in active-layer depth can cause subsidence at the surface, a lowering of the soil water table [46], and, potentially, thermokarst erosion [47].

Effects of climate change on landscape and regional processes and feedbacks to the climate system in the Arctic 2009

Current models suggest that arctic vegetation and active-layer soils will be a sink for C in the long term because of the northward movement of vegetation zones that are more productive than those they displace.

Uncertainties in the understanding of ecological processes and changes driven by climate and UV-B radiation 2009

A simple mechanistic model of tundra CH4 emissions that included the combined effects of temperature, moisture, and active-layer depth also suggested significant changes in CH4 emissions as a result of climate change [97].

Effects of changes in climate and UV radiation levels on function of arctic ecosystems in the short and long term 2009

With the first two methods, it is necessary to estimate the maximum active-layer thickness and the maximum permafrost temperature as a function of depth that the structure will be subjected to in its lifetime.

Infrastructure and climate in the Arctic 2009