Different geophysical methods are used to study and map submarine permafrost on the Arctic Shelf. Due to specific features of submarine permafrost, none of geophysical methods can provide conclusive data when gas-charged sediments and taliks occur within permafrost. Experimental data show that electrical properties of frozen grounds change significantly. For example, depending on ground lithology and wetness, electrical resistivity can increase up to 103 times upon freezing. Thus, electromagnetic methods could be considered more informative and valuable tool for characterizing subsea permafrost.
Investigation of submarine permafrost on the shallow Arctic Shelf requires modifications of electromagnetic methods to cover specific needs of working from the fast ice. Winter expeditions devoted to subsea permafrost investigations were performed in 2012-2014 in the near-shore area of the Laptev Sea. TEM was applied to predict permafrost down to 1 km depth. TEM systems are advantageous when many stations are required, because many short deployments can be performed in a single survey. Working from the fast ice allowed collection of few tens of stations to cover the entire polygon. Interpretation of data collected in 2012 allowed to predict position of the permafrost table near-shore in the vicinity of Muostakh Island, which was validated by followed up permafrost drilling. Accuracy of the methods reached 3.5%. Surveys performed in 2013-2014 also confirmed good agreement between electromagnetic data and observational data obtained by drilling.