Lecture 1 - Introduction

Periglacial environments can be cold wet or cold dry, generally alpine environments are wetter due to relief, and arctic environments are dry (arid). Permafrost, found in periglacial environments, soil/moisture that remains There is an active layer that thaws during summer, and also a transient layer between the two. The active layer is supra-permafrost, and is seasonally frozen. Usually seasonally frozen ground penetrates t the permafrost table, however if there is unfrozen ground twixt them, it is Talik. http://www.scienceinschool.org/repository/images/issue22permafrost9_xl.jpg Generally glacial landscapes are higher energy that periglacial, changing climate over time changes the prominent  landscape type and therefore the energy in the system. Proglacial environment: forms along ice boundaries and are periglacial in nature. Paraglacial environment: the environment is in disequilibrium between states/climate types. i.e. glacial -> temperate. French defined boundary conditions as less than 3 degrees air temperature (the same condition must be met for soilufluction and patterned ground, further categorization includes mean annual air temp less than -2 where frost action dominates. Tricart and Cailleux defined three periglacial environment types: 

Dry climates and severe winters, permafrost is characteristic. Humid climates with severe winter, permafrost is irregular in occurrence and distribution. Small annual temperate range, permafrost is absent.

Types of periglacial environment: High Arctic environments: Polar latitude, weak diurnal variation, strong seasons, small daily & large annual temp range. E.G. Canadian arctic. Continental climates: Sub-arctic latitude, weak diurnal, strong seasons, extreme annual temp range. E.G. Alaska & Yukon. Alpine climates: Middle latitude, well developed diurnal and seasonal patterns. E.G. Alps. Tibetan Plateau: Low Latitude, High elevation = High insolation, Strong seasonal and diurnal patterns, causes fierce freeze/thaw cycles. Climates of low annual temp range: Sub arctic latitudes Island climates E.G. South Georgia OR Mountain climates in low lats E.G. Andean summits.

Kane & Hinzman (2003): Stresses on the periglacial environment manifest in climate change, land use change and forest fires.Warmer permafrost = deeper active layer.Permafrost and overlying veg have a complex relationship, influencing thermal regime and moisture levels. Overlying veg is strongly impacted by logging and fires.

Smith and Riseborough (2002): TTOP model (1996) by smith and riseborough attempts to link the temperature at The Top Of Permafrost and the atmospheric temperature.Brown 1970, Observed that the boundary for continuous permafrost is at -8 degrees Mean Annual Air Temperature, whereas discontinuous permafrost can exist at -1.It is not simplys latitudinal though, veg, topology, snow cover etc all affect Mean Annual Ground Temperature (MAGT) which also affects permafrost incidence.MAGT is strongly governed by MAAT though.TTOP (mean annual top of permafrost) = MAAT + Surface Offset + Thermal OffsetSurface offset = MAAT - MAGSTThermal offset = MAGST - TTOPInterplay between MAAT, MAGST and therefore surface/thermal offset defines whether permafrost forms.Snow cover greatly influences the MAGST, therefore surface and thermal offset and so is key for determining the southern most limit of permafrost occurrence.

Kneisel 2010: Glacial retreat generally leaves favorable permafrost formation conditions. (coarse surface improves thermal regime).Below tree line low altitude (Swiss alps), thinner active layer than expected - organic material helps insulate and controls thermal regime.

New Page

Supplementary reading