21st century evolution of Antarctic permafrost
- This page is part of the topic Antarctic climate and environment change over the next 100 years
Although we do not envisage a major reduction in permafrost area over the next 100 years, melting of ground ice may lead to subsidence over some 15,000 km2 of Antarctica’s ice-free regions. Areas that are particularly susceptible to this effect, known as thermokarst, occur in coastal areas including Casey Bay near Molodezhnaya Station (70.5ºS, 12ºE), the Pennell-Borchgrevink Coasts in North Victoria land (70.5-73ºS, 165-171ºE), the Scott Coast in the McMurdo Sound area (74-78ºS, 165ºE), and throughout the Antarctic Peninsula and its offshore islands (55-72ºS, 45-70ºW).
In recent years there have been significant changes in hydrologic and geomorphologic processes as a consequence of unusual local summer warming events. For example, in the McMurdo Dry Valleys (MDV), the mean summer temperature (December and January) during the period 1994 to 2003 was -0.19ºC, and there were 30 days per year during that period in which the mean daily temperature was above 0ºC. During December 2000-January 2001, the mean temperature was 1.5ºC, and there were 43 days in which the mean daily temperature exceeded 0ºC. This protracted warming event resulted in flooding of rivers and expansion of inland lakes. (see also Foreman et al., 2004). These extreme events may have long-lasting effects. For example, after the December 2001 “wet event” in the MDV, soil moisture in Taylor Valley remained about twice the level of the preceding 9 years for a 4-year period (Barrett, unpublished). Observations suggest that extreme events in the MDV may alter subsurface flow and increase the hyporheic zone (the region beneath and lateral to a stream bed, where there is mixing of shallow groundwater and surface water), cause flushing of salts from soils, and reactivate sand wedges and ice wedges.
About 90% of the year-round summer bases in Antarctica are in areas sensitive to thermokarst formation and mass wasting. For that reason, the effect of climate warming on melting permafrost should be of concern to the Council of Managers of National Antarctic Programs (COMNAP). Examples exist of unusual warming at McMurdo Station causing road failure and undercutting pilings for utility corridors.
In the Arctic and central Asian regions, the melting of permafrost carries with it the threat of the release of the greenhouse gas methane. There is no significant risk of that in the Antarctic, where the soils, particularly in interior regions, contain very small amounts of organic C (<0.05%).
- Foreman, C.M., Wolf, C.F. and Priscu, J.C. 2004. Impact of episodic warming events on the physical, chemical and biological relationships of lakes in the McMurdo Dry Valleys, Antarctica, Aquatic Geochemistry, 10, 239-268.