LD2-2: Changes in fire regime are more important than climate warming in causing talik formation and loss of shallow permafrost.

The modeling technique that will be used in the proposed research will be the “permafrost temperature reanalysis” approach described in our recent publications (Romanovsky et al., 2002; Romanovsky et al., 2003). A sophisticated numerical model (Romanovsky and Osterkamp, 2000; Tipenko and Romanovsky, 2001; Sergueev et al., 2003), which takes into account the temperature-dependent latent heat effects and unfrozen water dynamics, will be used to reproduce active layer and permafrost temperature field dynamics at the specific sites with maximum available information. There will be three or four of such sites. The input data will be prescribed specifically for each site and will include detailed description of soils thermal properties and moisture for each distinct layer, the surface vegetation, and, with daily or monthly resolution, the snow cover depth and density and the air temperature dynamics. In this modeling method that was successfully used in the past (Romanovsky et al., 1997; Osterkamp and Romanovsky, 1999; Romanovsky and Osterkamp, 2001), variations in the air temperature and snow cover thickness and properties are the driving forces of the permafrost temperature dynamics. The model is calibrated for a specific site using a subset of measured permafrost and active layer temperatures at this site (usually several years of available data are used) and data from the closest meteorological station for the same time interval. The second subset of measured data that was not used in the calibration serves for the calibrated model validation. The calibrated model can then be applied to the entire period of meteorological records at this station, producing a time series of permafrost temperature changes. The same calibrated model can be applied for predictions of the future permafrost dynamics when some future climate change scenario is used as input data. In our proposed studies we will vary the soil properties in accordance with impact of forest fires on organic layer integrity and on soil moisture. An example of such numerical experiment could be found in (Yoshikawa et al., 2002).

References

Osterkamp, T. E., and V. E. Romanovsky, Evidence for warming and thawing of discontinuous permafrost in Alaska, Permafrost and Periglacial Processes, 10(1), 17-37, 1999.

Romanovsky, V.E., T.E. Osterkamp, and N. Duxbury, An evaluation of three numerical models used in simulations of the active layer and permafrost temperature regimes, Cold Regions Science and Technology, Vol. 26, No. 3, pp. 195-203, 1997.

Romanovsky, V. E., and T. E. Osterkamp, Effects of unfrozen water on heat and mass transport processes in the active layer and permafrost, Permafrost and Periglacial Processes, 11, 219-239, 2000.

Romanovsky, V. E., and Osterkamp, T. E., Permafrost: Changes and Impacts, in: R. Paepe and V. Melnikov (eds.), “Permafrost Response on Economic Development, Environmental Security and Natural Resources”, Kluwer Academic Publishers, 297-315, 2001.

Romanovsky, V., Burgess, M., Smith, S., Yoshikawa, K., and J. Brown, Permafrost Temperature Records: Indicators of Climate Change, EOS, AGU Transactions, Vol. 83, No. 50, 589-594, December 10, 2002.

Romanovsky, V. E., Sazonova, T. S., Tipenko G. S. and S. S. Marchenko, Establishing Permafrost Temperature Data Reanalysis, Eos. Trans. AGU, 84(47), Fall Meet. Suppl., Abstract, 2003.

Sergueev, D., Tipenko, G., Romanovsky, V., and N. Romanovskii, Mountain permafrost thickness evolution under influence of long-term climate fluctuations (results of numerical simulation). In: Proceedings of the VII International Permafrost Conference, Switzerland, July 21-25, pp. 1017-1021, 2003.

Tipenko, G. S. and V. E. Romanovsky, Simulation of Soil Freezing and Thawing: Direct and Inverse Problems, EOS, Trans. AGU, 82 (47), Fall Meet. Suppl., Abstract, F551, 2001.

Yoshikawa, K., Bolton, W. R., Romanovsky,V. E., Fukuda, M., and L. D. Hinzman, Impacts of Wildfire on the Permafrost in the Boreal Forests of Interior Alaska, Journal of Geophysical Research, 107, 8148, doi:10.1029/2001JD000438, 2002. [printed 108(D1), 2003]