THERMAL STATE OF PERMAFROST IN ALASKA DURING THE LAST 20 YEARS

• Main Author: V. E. Romanovsky
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic; Fairbanks; Active layer thickness; permafrost; Alaska
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.373.2549; http://www.lter.uaf.edu/dev2009/pdf/1069_romanofsky.pdf

Permafrost temperatures were on the rise during the last 20 years in Alaska. Generally, an increase in permafrost temperatures in Alaska during the last two decades was more pronounced at the coastal Arctic sites (from 1.5 to 3.0°C at the permafrost table) and less pronounced in the Interior Alaska (from 0.5 to 1.5°C). This increase in permafrost temperatures was not monotonous. During the observational period, relative cooling occurred in the early 1990s (late 1980s in the Interior Alaska) and then again in the early 2000s. Unlike the permafrost temperatures, data on changes in the active layer thickness in Alaska are less conclusive. While some of the sites show a slightly noticeable increasing trend, most of them do not. The active layer was especially deep in 2005 in Interior Alaska. At many sites, the active layer developed during the summer of 2004 (one of the warmest summers in Fairbanks on record) was the deepest observed in the past 10 years and did not completely freeze during the 2004-2005 winter. At some locations within the discontinuous permafrost of the Alaska interior, permafrost is presently thawing in natural undisturbed conditions. Deepening of the permafrost table from 3.5 m in 1989 to 5 m in 2004 was observed within some areas at the Gakona Permafrost Observatory in central Alaska. However, a more common cause is the disturbances of the ground surface above the permafrost, both natural (forest fire, flood) and human-made (agricultural activities, roads and building constructions, etc).