| Summary: | Empirical data as well as modelling experiments show that the stability of the Arctic cryosphere is today under threat due to global warming. Along the circum-arctic ocean periphery this cryosphere is comprised of terrestrial permafrost. However, during Quaternary times this frozen landscape was repeatedly changed due to global sea-level fluctuations which particularly affected the wide and shallow Siberian shelves. As western part of the Beringian landmass the entire Laptev Sea shelf was subaerially exposed in last glacial times. During the ensuing postglacial global sea-level rise this region gradually changed from a terrestrial permafrost landscape into a shallow marine shelf environment. Various geochemical, micropaleontological, palynological, and sedimentological data obtained from both conventional gravity cores and drill cores reveal the strong influence of this tranformation process on the shelf environment. Our previous scientific drilling campaign (2000), conducted to the outer Laptev Sea shelf with the goal to recover pre-Holocene sediments from acoustically transparent sections, confirmed the existence of frozen, and ice-bearing terrestrial sediments below a soft, marine sediment package of Holocene age. However, oxygen isotope composition of the ice unveiled that these frozen sediments must have been altered by re-freezing processes during and after the transgression. This assumption seems now corroborated by new high-resolution acoustic data from the mid- to inner shelf region gained during the latest expeditions in 2004. Although the overall scenario of shelf transformation for the time since the last sea level rise seems to be reasonably well understood now, there is no information available so far from older climatic intervals with conditions comparable to the Holocene. But such information from Holocene-like climate intervals will contribute useful insight for predictive purposes, since these records would then provide a longer time frame within which to evaluate natural variability in ...
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