HR: 17:40h
AN: A24C-07 INVITED     [Abstracts]
TI: Changes in Northern Eurasian Permafrost
AU: * Romanovsky, V E
EM: ffver@uaf.edu
AF: Geophysical Institute, UAF, 903 Koyukuk Drive POBox 757320, Fairbanks, AK 99775 United States
AB: Permafrost occupies a significant portion of Northern Eurasia. The large observed and predicted future climatic changes will inevitably change the energy and mass fluxes at the land surface and, as a result, the near-surface and subsurface physical conditions in northern Eurasia. This will trigger changes in ecosystems that will be largest in the permafrost areas because of the extreme sensitivity of the natural systems in these regions. The stability of the ecosystems in the permafrost regions relies on the stability of ice that so far holds these systems together. In losing permafrost the systems lose their stability. Thus, even if some ecosystems could avoid disintegration, their characteristics will be changed dramatically. Analysis of the long-term records of the near-surface permafrost temperature, obtained from different parts of the permafrost zone in northern Eurasia, shows a significant warming trend during the last 30 years. Ground temperature trends generally follow the trends in the air temperatures with more pronounced warming in the lower latitudes (between 55ø and 65ø North). This recent climate warming brought soil temperatures in Northern Eurasia to a surprisingly high level, about 1 to 3øC warmer than long-term averages. Within some areas the permafrost temperatures now are very close to 0øC and at some sites a long-term permafrost degradation already started. If recent trends continue, it will take several centuries to millennia for permafrost in the present discontinuous zone to disappear completely in the areas where it is now actively warming and thawing. However, negative consequences of this degradation will be pronounced from the very beginning because the highest ice content in permafrost usually is found in the upper few tens of meters. While the increase in permafrost temperatures may change many of its physical properties that can have some negative effects on infrastructure, the major threshold occurs when permafrost starts to thaw from its top down. At this moment, many processes (some of them very destructive) will be triggered or intensified. The most significant impacts on ecosystems, infrastructure, carbon cycle and hydrology will be observed in areas where permafrost contains a considerable amount of ground ice. Several specific examples of the past (measured) and predicted future (calculated) changes in permafrost will be discussed.
DE: 3210 Modeling
DE: 1823 Frozen ground
DE: 1600 GLOBAL CHANGE (New category)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting