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Glacial isostatic adjustment; Hydro-isostasy; Marine permafrost; Marine transgression
Abstract:
The Laptev Sea and East Siberian Sea are extended shallow shelf seas which were largely land fallen during glacial periods when the global mean sea level was more than 100 m below its present value. To understand the environmental history, and, in particular, the evolution of the large offshore permafrost complexes in this region, a reconstruction of the sea-level variation and shoreline migration was undertaken. Sufficient geological information by sea-level indicators is missing and, in recent studies, the eustatic sea-level curve is commonly applied, neglecting any isostatic adjustment processes. In this study, we discuss the influence of glacial isostatic adjustment (GIA), which describes the deformational response of the solid earth and the resulting sea-level variations due to the water mass redistribution between ice sheets and ocean during a glacial cycle. Motivated as a sensitivity study, we consider GIA-induced sea-level variations from the last glacial maximum (LGM) to present and apply an earth model ensemble which covers the range of reasonable rheological parametrisations for a passive continental margin. The geodynamically consistent sea-level reconstructions are applied to predict the shoreline retreat in the Laptev and East Siberian seas. We confirm with this study that the application of the eustatic sea-level curve is a valid first-order approximation for reconstructing the shoreline position from LGM to present, whereas the sea-level heights away from the shoreline inferred from the eustatic sea-level curve differ markedly from GIA predictions.
