Present-day knowledge of the development of permafrost

Knowledge of the development of permafrost has been arrived at gradually. In the 1930s M.L Sumgin substantiated the theory of the degradation of permafrost (with warming, thawing and northward retreat). Having compared the severe climate of glacial epochs with the warmer present one, Sumgin came to the conclusion that the permafrost formed simultaneously with the ice sheets and had subsequently thawed retreating northward, i.e. it had degraded. He presented data indicating displacement of the southern limit of permafrost northward. However such researchers as S.G. Parkhomenko, P.I. Koloskov, P.N. Kapterev, D.V. Redozubov and others pointed out the fact of new permafrost formation, permafrost temperature decrease and its increase in thickness in other regions of the country. Contrary to Sumgin they followed the alternative theory – that of aggradation, i.e. they reasoned that the process of permafrost advance is taking place at the present time. According to their views the permafrost is a result of recent heat exchange (the last 3–5 thousand years) in the system ‘atmosphere-lithosphere’. These two points of view were antagonistic for 10–15 years and only V.A. Kudryavtsev's basic works (1953–1963) clarifying the basis for the present theory of permafrost development gave the proper interpretation of these points of view.