On the thermal influence of thermokarst lakes on the subsea permafrost evolution

Abstract

A one-dimensional model for the heat transfer with a phase change is proposed to simulate the dynamics of the subsea permafrost on the Laptev Sea shelf. By now we investigate the evolution of the subsea permafrost since the last glacial maximum, taking into account a possible development of the thermokarst lakes. This paper also discusses the permafrost-related gas hydrate stability zone. The permafrost within most of the Laptev Sea shelf (≤ 50 m water depth) is estimated as 440 - 560 m given a heat flow of 60 mW/m 2 , and 178 - 265 m given a heat flow of 100 mW/m 2 . The thermokarst lakes play an important role in the heat exchange between the atmosphere and sediments. The subsea permafrost evolution also depends on thermokarst lakes existence. Scenarios show that the permafrost thawing from top to bottom leads to the formation of the closed talik. The effect of a heat flux for fault zones results in higher sediment temperatures and in a more rapid destruction of the permafrost and hydrate zone. The proposed model predicts the development of open taliks at the shelf sites with water depths of 10 – 20 m in active tectonic faults.