Abstract
Abstract. The evolution of permafrost on the Kara shelf is reconstructed for the past 125 kyr. The work includes zoning of the shelf according to geological history; compiling sea level and ground temperature scenarios within the distinguished zones; and modeling to evaluate the thickness of permafrost and the distribution of frozen, cooled and thawed deposits. Special attention is given to the scenarios of the evolution of ground temperature in key stages of history that determined the current state of the Kara shelf permafrost zone: characterization of the extensiveness and duration of the existence of the sea during stage 3 of the marine oxygen isotope stratigraphy (MIS-3), the spread of glaciation and dammed basins in MIS-2. The present shelf is divided into areas of continuous, discontinuous-to-sporadic and sporadic permafrost. Cooled deposits occur at the western and northwestern water zones and correspond to areas of MIS-2 glaciation. Permafrost occurs in the periglacial domain that is within a zone of modern sea depth from 0 to 100 m, adjacent to the continent. The distribution of permafrost is mostly sporadic in the southwest of this zone, while it is mostly continuous in the northeast. The thickness of permafrost does not exceed 100 m in the southeast and ranges from 100 to 300 m in the northeast. Thawed deposits are confined to the estuaries of large rivers and the deepwater part of the St. Anna trench. The modeling results are correlated to the available field data and are presented as a geocryological map. The formation of frozen, cooled and thawed deposits of the region is inferred to depend on the spread of ice sheets, sea level, and duration of shelf freezing and thawing periods.
Highlights
Permafrost studies and mapping on the Kara Sea shelf (Fig. 1) have a long history
We focused on recreating the Late Pleistocene–Holocene transgression (Fig. 4a, b)
The simulation results show that the distribution of deposits that differ in their state is associated with the paleogeographic events of the Late Pleistocene–Holocene
Summary
Permafrost studies and mapping on the Kara Sea shelf (Fig. 1) have a long history. The first evidence of its distribution in the Kara and other Eurasian Arctic shelves appeared in early permafrost maps of the USSR (Parkhomenko, 1937; Baranov, 1960). The available data are restricted to the southwestern part of the shelf, while the northeastern part remains poorly documented and undrilled Another recent map of permafrost distribution and thickness on the southwestern Kara shelf (Portnov et al, 2013) is based on seismoacoustic data and modeling with reference to the glacial eustatic curve but without regard to regional features related to the existence of marine oxygen isotope stratigraphy cold stage 3 (MIS-3) marine terraces. Given the logistic challenge and high costs of field studies, knowledge of the Kara shelf permafrost can be extended by numerical modeling Its application makes it possible to establish the connection of permafrost with components of the natural environment, including glaciations, glacio-isostatic movements and sea level fluctuations
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